sign in sign up
<<
Home , 1639 transit of Venus, 2004 transit of Venus, 2007 WD5, 2008 LC18, 2009 BD, 3 Juno

paper Contents

1 1 1.1 Structure ...... 1 1.1.1 Composition ...... 1 1.1.2 and size ...... 2 1.1.3 Internal structure ...... 2 1.2 ...... 3 1.2.1 layers ...... 3 1.2.2 Great Spot and other vortices ...... 4 1.3 Planetary rings ...... 4 1.4 ...... 5 1.5 and rotation ...... 5 1.6 Observation ...... 6 1.7 Research and exploration ...... 6 1.7.1 Pre-telescopic research ...... 6 1.7.2 Ground-based research ...... 7 1.7.3 Radiotelescope research ...... 8 1.7.4 Exploration with space probes ...... 8 1.8 ...... 9 1.8.1 ...... 10 1.8.2 Classification of moons ...... 10 1.9 Interaction with the Solar System ...... 10 1.9.1 Impacts ...... 11 1.10 Possibility of ...... 12 1.11 Mythology ...... 12 1.12 See also ...... 12 1.13 Notes ...... 13 1.14 References ...... 13 1.15 Further reading ...... 18 1.16 External links ...... 18

2 19 2.1 Physical characteristics ...... 19 2.1.1 Internal structure ...... 20

i ii CONTENTS

2.1.2 Surface ...... 20 2.1.3 ...... 21 2.1.4 Hydrology ...... 21 2.1.5 Geography and naming of surface features ...... 23 2.1.6 Atmosphere ...... 26 2.1.7 Climate ...... 28 2.2 Orbit and rotation ...... 28 2.3 Search for life ...... 29 2.4 Habitability ...... 30 2.5 Exploration missions ...... 30 2.6 on Mars ...... 30 2.7 Viewing ...... 31 2.7.1 Closest approaches ...... 32 2.8 Historical observations ...... 32 2.8.1 Ancient and medieval observations ...... 33 2.8.2 “canals” ...... 33 2.8.3 visitation ...... 34 2.9 In culture ...... 34 2.9.1 Intelligent “” ...... 34 2.10 Moons ...... 36 2.11 Gallery ...... 37 2.12 See also ...... 37 2.13 Notes ...... 37 2.14 References ...... 37 2.15 External links ...... 45

3 47 3.1 Common meanings ...... 47 3.2 Places ...... 47 3.3 In the military ...... 47 3.4 Transportation ...... 47 3.5 In entertainment ...... 47 3.5.1 Music ...... 47 3.5.2 Comics ...... 48 3.5.3 Other ...... 48 3.6 Technology ...... 48 3.6.1 Computing ...... 48 3.7 Sports ...... 48 3.8 Publications ...... 48 3.9 Radio stations ...... 48 3.10 In business ...... 48 3.11 Other uses ...... 48 CONTENTS iii

3.12 See also ...... 49

4 50 4.1 History ...... 50 4.1.1 Discovery ...... 50 4.1.2 Naming ...... 51 4.1.3 Status ...... 52 4.2 Composition and structure ...... 52 4.2.1 Internal structure ...... 52 4.2.2 Atmosphere ...... 52 4.2.3 Magnetosphere ...... 53 4.3 Planetary rings ...... 54 4.4 Climate ...... 54 4.4.1 ...... 55 4.4.2 Internal heating ...... 55 4.5 Orbit and rotation ...... 56 4.5.1 Orbital resonances ...... 56 4.6 Formation and migration ...... 57 4.7 Moons ...... 57 4.8 Observation ...... 58 4.9 Exploration ...... 58 4.10 See also ...... 59 4.11 Notes ...... 59 4.12 References ...... 59 4.13 Bibliography ...... 64 4.14 Further reading ...... 64 4.15 External links ...... 64

5 65 5.1 Physical characteristics ...... 65 5.1.1 Internal structure ...... 65 5.2 Atmosphere ...... 66 5.2.1 Cloud layers ...... 66 5.2.2 North pole hexagonal cloud pattern ...... 67 5.2.3 pole vortex ...... 67 5.2.4 Other features ...... 68 5.3 Magnetosphere ...... 68 5.4 Orbit and rotation ...... 68 5.5 Planetary rings ...... 69 5.6 Natural ...... 69 5.7 History of exploration ...... 70 5.7.1 Ancient observations ...... 70 iv CONTENTS

5.7.2 European observations (17th–19th centuries) ...... 70 5.7.3 Modern NASA and ESA probes ...... 71 5.8 Observation ...... 72 5.9 In culture ...... 73 5.10 See also ...... 74 5.11 Notes ...... 74 5.12 References ...... 74 5.13 Further reading ...... 78 5.14 External links ...... 79

6 80 6.1 History ...... 80 6.1.1 Discovery ...... 80 6.1.2 Naming ...... 81 6.1.3 Name ...... 82 6.2 Orbit and rotation ...... 82 6.2.1 ...... 83 6.2.2 Visibility ...... 83 6.3 Internal structure ...... 83 6.3.1 Internal heat ...... 84 6.4 Atmosphere ...... 84 6.4.1 Composition ...... 84 6.4.2 Troposphere ...... 85 6.4.3 Upper atmosphere ...... 85 6.5 Planetary rings ...... 86 6.6 Magnetosphere ...... 86 6.7 Climate ...... 87 6.7.1 Banded structure, winds and ...... 87 6.7.2 Seasonal variation ...... 88 6.8 Formation ...... 89 6.9 Moons ...... 89 6.10 Exploration ...... 90 6.11 In culture ...... 90 6.12 See also ...... 91 6.13 Notes ...... 91 6.14 References ...... 91 6.15 Further reading ...... 96 6.16 External links ...... 96

7 97 7.1 Physical characteristics ...... 97 7.1.1 Geography ...... 97 CONTENTS v

7.1.2 Surface geology ...... 98 7.1.3 Internal structure ...... 99 7.1.4 Atmosphere and climate ...... 99 7.1.5 Magnetic field and core ...... 101 7.2 Orbit and rotation ...... 101 7.3 Observation ...... 102 7.3.1 Transits ...... 103 7.3.2 ...... 103 7.4 Studies ...... 103 7.4.1 Early studies ...... 103 7.4.2 Ground-based research ...... 104 7.5 Exploration ...... 104 7.5.1 Early efforts ...... 105 7.5.2 ...... 105 7.5.3 Surface and ...... 105 7.5.4 mapping ...... 107 7.5.5 Current and future missions ...... 107 7.5.6 Manned fly-by concept ...... 108 7.5.7 Sample return ...... 108 7.5.8 Spacecraft timeline ...... 108 7.6 In culture ...... 108 7.6.1 Etymology ...... 108 7.6.2 Venus symbol ...... 108 7.7 Colonization and ...... 109 7.8 See also ...... 109 7.9 Notes ...... 109 7.10 References ...... 109 7.11 External links ...... 114 7.11.1 Cartographic resources ...... 115 7.12 Text and sources, contributors, and licenses ...... 116 7.12.1 Text ...... 116 7.12.2 Images ...... 127 7.12.3 Content license ...... 135 Chapter 1

Jupiter

This article is about the . For the Roman god, 1.1 Structure see Jupiter (mythology). For other uses, see Jupiter (disambiguation). Jupiter is composed primarily of gaseous and liquid matter. It is the largest of the four giant planets in the Jupiter is the fifth planet from the and the largest Solar System and hence its largest planet. It has a diame- planet in the Solar System. It is a with ter of 142,984 km (88,846 mi) at its . The a mass one-thousandth of that of the Sun, but is two of Jupiter, 1.326 g/cm3, is the highest of the giant and a half times that of all the other planets in the So- planets, but lower than those of the four terrestrial plan- lar System combined. Jupiter is a , along with ets. Saturn (Uranus and Neptune are giants). Jupiter was known to of ancient times.*[11] The Romans named it after their god Jupiter.*[12] When 1.1.1 Composition viewed from , Jupiter can reach an apparent mag- nitude of −2.94, bright enough to cast shadows,*[13] and Jupiter's upper atmosphere is composed of about 88– making it on average the third-brightest object in the 92% and 8–12% by percent volume of night sky after the and Venus.(Mars can briefly gas molecules. Because a helium atom has about four match Jupiter's brightness at certain points in its orbit.) times as much mass as a hydrogen atom, the composi- Jupiter is primarily composed of hydrogen with a quar- tion changes when described as the proportion of mass ter of its mass being helium, although helium only com- contributed by different atoms. Thus, the atmosphere is prises about a tenth of the number of molecules. It may approximately 75% hydrogen and 24% helium by mass, also have a rocky core of heavier elements,*[14] but like with the remaining one percent of the mass consisting the other giant planets, Jupiter lacks a well-defined solid of other elements. The interior contains denser materi- surface. Because of its rapid rotation, the planet's shape als, such that the distribution is roughly 71% hydrogen, is that of an oblate (it has a slight but notice- 24% helium and 5% other elements by mass. The atmo- able bulge around the equator). The outer atmosphere sphere contains trace amounts of , vapor, is visibly segregated into several bands at different lat- , and -based compounds. There are also itudes, resulting in turbulence and storms along their in- traces of , ethane, hydrogen sulfide, , , phosphine, and . The outermost layer of the at- teracting boundaries. A prominent result is the Great Red * * Spot, a giant that is known to have existed since at mosphere contains crystals of frozen ammonia. [15] [16] least the 17th century when it was first seen by telescope. Through and measurements, trace amounts of and other hydrocarbons have also Surrounding Jupiter is a faint planetary and a * powerful magnetosphere. Jupiter has at least 67 moons, been found. [17] including the four large Galilean moons discovered by The atmospheric proportions of hydrogen and helium are Galilei in 1610. , the largest of these, close to the theoretical composition of the primordial has a diameter greater than that of the planet Mercury. solar . Neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as Jupiter has been explored on several occasions by robotic * spacecraft, most notably during the early Pioneer and abundant as in the Sun. [18] Helium is also depleted, to Voyager flyby missions and later by the Galileo orbiter. about 80% of the Sun's helium composition. This deple- tion is a result of precipitation of these elements into the The most recent probe to visit Jupiter was the - * bound spacecraft in late February 2007. interior of the planet. [19] Abundances of heavier inert The probe used the from Jupiter to increase its gases in Jupiter's atmosphere are about two to three times speed. Future targets for exploration in the Jovian sys- that of the Sun. tem include the possible ice-covered liquid ocean on the Based on , Saturn is thought to be simi- moon . lar in composition to Jupiter, but the other giant plan-

1 2 CHAPTER 1. JUPITER

ets Uranus and Neptune have relatively much less - creasing mass would continue until appreciable stellar ig- drogen and helium.*[20] Because of the lack of atmo- nition is achieved as in high-mass dwarfs having spheric entry probes, high-quality abundance numbers of around 50 Jupiter .*[27] the heavier elements are lacking for the outer planets be- Although Jupiter would need to be about 75 times as yond Jupiter. massive to fuse hydrogen and become a , the small- est is only about 30 percent larger in radius than Jupiter.*[28]*[29] Despite this, Jupiter still radiates 1.1.2 Mass and size more heat than it receives from the Sun; the amount of heat produced inside it is similar to the total solar radia- tion it receives.*[30] This additional heat is generated by the –Helmholtz mechanism through contraction. This process causes Jupiter to shrink by about 2 cm each .*[31] When it was first formed, Jupiter was much hotter and was about twice its current diameter.*[32]

1.1.3 Internal structure

Jupiter is thought to consist of a dense core with a mixture of elements, a surrounding layer of liquid metallic hydro- gen with some helium, and an outer layer predominantly of molecular hydrogen.*[31] Beyond this basic outline, there is still considerable uncertainty. The core is often described as rocky, but its detailed composition is un- known, as are the properties of materials at the tempera- tures and pressures of those depths (see below). In 1997, the existence of the core was suggested by gravitational measurements,*[31] indicating a mass of from 12 to 45 Jupiter's diameter is one order of smaller (×0.10045) times the Earth's mass or roughly 4%–14% of the total than the Sun, and one order of magnitude larger (×10.9733) mass of Jupiter.*[30]*[33] The presence of a core during than the Earth. The has roughly the same size as at least part of Jupiter's history is suggested by models of the circumference of the Earth. planetary formation that require the formation of a rocky or icy core massive enough to collect its bulk of hydro- Jupiter's mass is 2.5 times that of all the other planets gen and helium from the protosolar nebula. Assuming it in the Solar System combined—this is so massive that did exist, it may have shrunk as currents of its barycenter with the Sun lies above the Sun's surface hot liquid metallic hydrogen mixed with the molten core at 1.068 solar radii from the Sun's center. Although this and carried its contents to higher levels in the planetary planet dwarfs the Earth with a diameter 11 times as great, interior. A core may now be entirely absent, as gravita- it is considerably less dense. Jupiter's volume is that tional measurements are not yet precise enough to rule of about 1,321 , but it is only 318 times as mas- that possibility out entirely.*[31]*[34] sive.*[4]*[21] Jupiter's radius is about 1/10 the radius of The uncertainty of the models is tied to the error margin the Sun,*[22] and its mass is 0.001 times the mass of the Sun, so the density of the two bodies is similar.*[23] A in hitherto measured parameters: one of the rotational coefficients (J6) used to describe the planet's gravitational ""(MJ or MJup) is often used as a unit to describe masses of other objects, particularly extrasolar moment, Jupiter's equatorial radius, and its planets and brown dwarfs. So, for example, the extrasolar at 1 bar pressure. The mission, which launched in August 2011, is expected to better constrain the values planet HD 209458 b has a mass of 0.69 MJ, while Kappa Andromedae b has a mass of 12.8 M .*[24] of these parameters, and thereby make progress on the J problem of the core.*[35] Theoretical models indicate that if Jupiter had much more mass than it does at present, it would shrink.*[25] For The core region is surrounded by dense metallic hydro- gen, which extends outward to about 78% of the ra- small changes in mass, the radius would not change appre- * * dius of the planet. [30] Rain-like droplets of helium and ciably, and above about 500 M⊕ (1.6 Jupiter masses) [25] the interior would become so much more compressed un- neon precipitate downward through this layer, deplet- ing the abundance of these elements in the upper atmo- der the increased pressure that its volume would decrease * * despite the increasing amount of matter. As a result, sphere. [19] [36] Jupiter is thought to have about as large a diameter as Above the layer of metallic hydrogen lies a transparent in- a planet of its composition and evolutionary history can terior atmosphere of hydrogen. At this depth, the temper- achieve.*[26] The process of further shrinkage with in- ature is above the critical temperature, which for hydro- 1.2. ATMOSPHERE 3

gen is only 33 K*[37] (see hydrogen). In this state, there are no distinct liquid and gas phases—hydrogen is said to be in a supercritical fluid state. It is convenient to treat hydrogen as gas in the upper layer extending downward from the cloud layer to a depth of about 1,000 km,*[30] and as liquid in deeper layers. Physically, there is no clear boundary—the gas smoothly becomes hotter and denser as one descends.*[38]*[39] The temperature and pressure inside Jupiter increase steadily toward the core, due to the Kelvin–Helmholtz mechanism. At the “surface”pressure level of 10 bars, the temperature is around 340 K (67 °C; 152 °F). At the phase transition region where hydrogen—heated be- yond its critical point—becomes metallic, it is believed the temperature is 10,000 K (9,700 °C; 17,500 °F) and the pressure is 200 GPa. The temperature at the core boundary is estimated to be 36,000 K (35,700 °C; 64,300 °F) and the interior pressure is roughly 3,000–4,500 This view of Jupiter's Great Red Spot and its surroundings was GPa.*[30] obtained by on February 25, 1979, when the space- craft was 9.2 million km (5.7 million mi) from Jupiter. The white oval storm directly below the Great Red Spot is approximately the same diameter as Earth.

color and intensity from year to year, but they have re- mained sufficiently stable for astronomers to give them identifying designations.*[21]

This cut-away illustrates a model of the interior of Jupiter, with a rocky core overlaid by a deep layer of liquid metallic hydrogen.

This looping animation shows the movement of Jupiter's counter- 1.2 Atmosphere rotating cloud bands. In this image, the planet's exterior is mapped onto a cylindrical projection. Animation at larger article: widths: 720 pixels, 1799 pixels.

The cloud layer is only about 50 km (31 mi) deep, and Jupiter has the largest planetary atmosphere in the So- consists of at least two decks of clouds: a thick lower lar System, spanning over 5,000 km (3,107 mi) in alti- deck and a thin clearer region. There may also be a tude.*[40]*[41] As Jupiter has no surface, the base of its thin layer of water clouds underlying the ammonia layer, atmosphere is usually considered to be the point at which as evidenced by flashes of detected in the at- atmospheric pressure is equal to 1 MPa (10 bar), or ten mosphere of Jupiter. This is caused by water's polarity, times surface pressure on Earth.*[40] which makes it capable of creating the charge separation needed to produce lightning.*[30] These electrical dis- 1.2.1 Cloud layers charges can be up to a thousand times as powerful as light- ning on the Earth.*[43] The water clouds can form thun- * Jupiter is perpetually covered with clouds composed of derstorms driven by the heat rising from the interior. [44] ammonia crystals and possibly ammonium hydrosulfide. The orange and brown coloration in the clouds of Jupiter The clouds are located in the tropopause and are ar- are caused by upwelling compounds that change color ranged into bands of different , known as tropi- when they are exposed to ultraviolet light from the cal regions. These are sub-divided into lighter-hued zones Sun. The exact makeup remains uncertain, but the sub- and darker belts. The interactions of these conflicting stances are believed to be , sulfur or possi- circulation patterns cause storms and turbulence. bly hydrocarbons.*[30]*[45] These colorful compounds, speeds of 100 m/s (360 km/h) are common in zonal known as chromophores, mix with the warmer, lower jets.*[42] The zones have been observed to vary in width, deck of clouds. The zones are formed when rising 4 CHAPTER 1. JUPITER

convection cells form crystallizing ammonia that masks out these lower clouds from view.*[46] Jupiter's low axial tilt means that the poles constantly re- ceive less solar than at the planet's equatorial region. Convection within the interior of the planet trans- ports more energy to the poles, balancing out the temper- atures at the cloud layer.*[21]

1.2.2 Great Red Spot and other vortices

Time-lapse sequence (over 1 ) from the approach of Voyager 1 to Jupiter, showing the motion of atmospheric bands, and circulation of the Great Red Spot. Full size video here

times around the planet relative to any possible fixed ro- tational marker below it. Jupiter – Great Red Spot is decreasing in size (May 15, 2014).*[47] In 2000, an atmospheric feature formed in the south- ern hemisphere that is similar in appearance to the Great The best known feature of Jupiter is the Great Red Spot, Red Spot, but smaller. This was created when several a persistent that is larger than Earth, smaller, white oval-shaped storms merged to form a sin- located 22° south of the equator. Latest evidence by gle feature—these three smaller white ovals were first ob- the shows there are three “red served in 1938. The merged feature was named Oval BA, spots”adjacent to the Great Red Spot*[48] It is known to and has been nicknamed Red Spot Junior. It has since have been in existence since at least 1831,*[49] and pos- increased in intensity and changed color from white to sibly since 1665.*[50]*[51] Mathematical models suggest red.*[57]*[58]*[59] that the storm is stable and may be a permanent feature of the planet.*[52] The storm is large enough to be vis- ible through Earth-based with an aperture of 1.3 Planetary rings 12 cm or larger.*[53] The oval object rotates counterclockwise, with a period of about six days.*[54] The Great Red Spot's dimensions are 24–40,000 km × 12–14,000 km. It is large enough to contain two or three planets of Earth's diameter.*[55] The maximum altitude of this storm is about 8 km (5 mi) above the surrounding cloudtops.*[56] Storms such as this are common within the turbulent of giant planets. Jupiter also has white ovals and brown ovals, which are lesser unnamed storms. White ovals tend to consist of relatively cool clouds within the upper atmosphere. Brown ovals are warmer and lo- cated within the“normal cloud layer”. Such storms can last as little as a few or stretch on for centuries. Even before Voyager proved that the feature was a storm, there was strong evidence that the spot could not be as- The sociated with any deeper feature on the planet's surface, as the Spot rotates differentially with respect to the rest Main article: Rings of Jupiter of the atmosphere, sometimes faster and sometimes more slowly. During its recorded history it has traveled several Jupiter has a faint planetary ring system composed of 1.5. ORBIT AND ROTATION 5

three main segments: an inner torus of particles known —a region between it and the bow shock. as the halo, a relatively bright main ring, and an outer The interacts with these regions, elongating gossamer ring.*[60] These rings appear to be made of the magnetosphere on Jupiter's lee side and extending it , rather than ice as with Saturn's rings.*[30] The main outward until it nearly reaches the orbit of Saturn. The ring is probably made of material ejected from the satel- four largest all orbit within the magne- lites and . Material that would normally tosphere, which protects them from the solar wind.*[30] fall to the moon is pulled into Jupiter because of its The magnetosphere of Jupiter is responsible for intense strong gravitational influence. The orbit of the material episodes of radio emission from the planet's re- veers towards Jupiter and new material is added by addi- * gions. Volcanic activity on the Jovian moon (see be- tional impacts. [61] In a similar way, the moons low) injects gas into Jupiter's magnetosphere, producing and probably produce the two distinct compo- * a torus of particles about the planet. As Io moves through nents of the dusty gossamer ring. [61] There is also evi- this torus, the interaction generates Alfvén waves that dence of a rocky ring strung along Amalthea's orbit which * carry ionized matter into the polar regions of Jupiter. As may consist of collisional debris from that moon. [62] a result, radio waves are generated through a cyclotron maser mechanism, and the energy is transmitted out along a cone-shaped surface. When the Earth intersects this 1.4 Magnetosphere cone, the radio emissions from Jupiter can exceed the so- lar radio output.*[64] Main article: Magnetosphere of Jupiter Jupiter's magnetic field is 14 times as strong as the 1.5 Orbit and rotation

Aurora on Jupiter. Three bright dots are created by magnetic flux tubes that connect to the Jovian moons Io (on the left), Ganymede (on the bottom) and Europa (also on the bottom). In addition, the bright almost circular region, called the main oval, and the fainter polar can be seen.

Earth's, ranging from 4.2 gauss (0.42 mT) at the equator to 10–14 gauss (1.0–1.4 mT) at the poles, making it the strongest in the Solar System (except for sunspots).*[46] This field is believed to be generated by eddy currents —swirling movements of conducting materials—within Jupiter (red) completes one orbit of the Sun (center) for every the liquid metallic hydrogen core. The volcanoes on the 11.86 of the Earth (blue) moon Io emit large amounts of forming a along the moon's orbit. The gas is ionized Jupiter is the only planet that has a center of mass with in the magnetosphere producing sulfur and oxygen ions. the Sun that lies outside the volume of the Sun, though by They, together with hydrogen ions originating from the only 7% of the Sun's radius.*[65] The average distance atmosphere of Jupiter, form a sheet in Jupiter's between Jupiter and the Sun is 778 million km (about equatorial plane. The plasma in the sheet co-rotates 5.2 times the average distance from the Earth to the Sun, with the planet causing deformation of the dipole mag- or 5.2 AU) and it completes an orbit every 11.86 . netic field into that of magnetodisk. Electrons within the This is two-fifths the of Saturn, forming generate a strong radio signature that pro- * a 5:2 between the two largest planets duces bursts in the range of 0.6–30 MHz. [63] in the Solar System.*[66] The elliptical orbit of Jupiter At about 75 Jupiter radii from the planet, the inter- is inclined 1.31° compared to the Earth. Because of action of the magnetosphere with the solar wind gen- an eccentricity of 0.048, the distance from Jupiter and erates a bow shock. Surrounding Jupiter's magneto- the Sun varies by 75 million km between perihelion and sphere is a , located at the inner edge of a aphelion, or the nearest and most distant points of the 6 CHAPTER 1. JUPITER planet along the orbital path respectively. The axial tilt of Jupiter is relatively small: only 3.13°. As a result this planet does not experience significant - sonal changes, in contrast to Earth and Mars for exam- ple.*[67] Jupiter's rotation is the fastest of all the Solar System's planets, completing a rotation on its axis in slightly less than ten hours; this creates an equatorial bulge easily seen through an Earth-based amateur telescope. The planet is shaped as an oblate spheroid, meaning that the diameter across its equator is longer than the diameter measured between its poles. On Jupiter, the equatorial diameter is The retrograde motion of an outer planet is caused by its relative 9,275 km (5,763 mi) longer than the diameter measured location with respect to the Earth. through the poles.*[39]

Because Jupiter is not a solid body, its upper atmosphere Earth overtakes Jupiter every 398.9 days as it orbits the undergoes differential rotation. The rotation of Jupiter's Sun, a duration called the synodic period. As it does polar atmosphere is about 5 minutes longer than that so, Jupiter appears to undergo retrograde motion with re- of the equatorial atmosphere; three systems are used as spect to the background . That is, for a period Jupiter frames of reference, particularly when graphing the mo- seems to move backward in the night sky, performing a tion of atmospheric features. System I applies from the looping motion. latitudes 10° N to 10° S; its period is the planet's shortest, at 9h 50m 30.0s. System II applies at all latitudes north Jupiter's 12-year orbital period corresponds to the dozen and south of these; its period is 9h 55m 40.6s. System III astrological signs of the , and may have been the * was first defined by radio astronomers, and corresponds historical origin of the signs. [21] That is, each time to the rotation of the planet's magnetosphere; its period Jupiter reaches it has advanced eastward by is Jupiter's official rotation.*[68] about 30°, the width of a zodiac sign. Because the orbit of Jupiter is outside the Earth's, the phase angle of Jupiter as viewed from the Earth never 1.6 Observation exceeds 11.5°. That is, the planet always appears nearly fully illuminated when viewed through Earth-based tele- scopes. It was only during spacecraft missions to Jupiter that views of the planet were obtained.*[70] A small telescope will usually show Jupiter's four Galilean moons and the prominent cloud belts across Jupiter's atmosphere.*[71] A large telescope will show Jupiter's Great Red Spot when it faces the Earth.

1.7 Research and exploration

1.7.1 Pre-telescopic research

The observation of Jupiter dates back to the Babylonian of Jupiter and the Moon astronomers of the 7th or 8th century BC.*[72] The Chi- nese historian of astronomy, Xi Zezong, has claimed that Jupiter is usually the fourth brightest object in the sky , a Chinese , made the discovery of (after the Sun, the Moon and Venus);*[46] at times Mars one of Jupiter's moons in 362 BC with the unaided . appears brighter than Jupiter. Depending on Jupiter's If accurate, this would predate Galileo's discovery by position with respect to the Earth, it can vary in visual nearly two millennia.*[73]*[74] In his 2nd century work magnitude from as bright as −2.9 at opposition down to the , the Hellenistic astronomer Claudius Ptole- −1.6 during conjunction with the Sun. The angular di- maeus constructed a geocentric planetary model based on ameter of Jupiter likewise varies from 50.1 to 29.8 arc deferents and epicycles to explain Jupiter's motion rela- .*[4] Favorable oppositions occur when Jupiter is tive to the Earth, giving its orbital period around the Earth passing through perihelion, an event that occurs once per as 4332.38 days, or 11.86 years.*[75] In 499, , orbit. As Jupiter approached perihelion in 2011, a mathematician–astronomer from the classical age of there was a favorable opposition in September 2010.*[69] Indian mathematics and astronomy, also used a geocen- 1.7. RESEARCH AND EXPLORATION 7

M ϕ r R θ A e e

False-color detail of Jupiter's atmosphere, imaged by Voyager 1, Model in the Almagest of the longitudinal motion of Jupiter () showing the Great Red Spot and a passing white oval. relative to the Earth ().

the Earth, these events would occur about 17 minutes tric model to estimate Jupiter's period as 4332.2722 days, later than expected. Ole Rømer deduced that sight is not or 11.86 years.*[76] instantaneous (a conclusion that had earlier re- jected),*[16] and this timing discrepancy was used to es- timate the speed of light.*[80] 1.7.2 Ground-based telescope research In 1892, E. E. observed a fifth of Jupiter In 1610, discovered the four largest with the 36-inch (910 mm) refractor at Lick Observa- moons of Jupiter—Io, Europa, Ganymede and tory in California. The discovery of this relatively small (now known as the Galilean moons)—using a telescope; object, a testament to his keen eyesight, quickly made thought to be the first telescopic observation of moons him famous. This moon was later named Amalthea.*[81] other than Earth's. Galileo's was also the first discovery It was the last planetary moon to be discovered directly of a celestial motion not apparently centered on the Earth. by visual observation.*[82] An additional eight satellites It was a major point in favor of Copernicus' heliocentric were discovered before the flyby of the Voyager 1 probe theory of the motions of the planets; Galileo's outspoken in 1979. support of the Copernican theory placed him under the threat of the Inquisition.*[77] During the , Cassini used a new telescope to dis- cover spots and colorful bands on Jupiter and observed that the planet appeared oblate; that is, flattened at the poles. He was also able to estimate the of the planet.*[16] In 1690 Cassini noticed that the atmo- sphere undergoes differential rotation.*[30] The Great Red Spot, a prominent oval-shaped feature in the southern hemisphere of Jupiter, may have been ob- served as early as 1664 by Robert and in 1665 by Giovanni Cassini, although this is disputed. The pharma- cist Heinrich Schwabe produced the earliest known draw- ing to show details of the Great Red Spot in 1831.*[78] The Red Spot was reportedly lost from sight on several occasions between 1665 and 1708 before becoming quite conspicuous in 1878. It was recorded as fading again in 1883 and at the start of the 20th century.*[79] Infrared image of Jupiter taken by ESO's . Both Giovanni Borelli and Cassini made careful tables of the motions of the Jovian moons, allowing predic- In 1932, Rupert Wildt identified absorption bands of am- tions of the times when the moons would pass before or * behind the planet. By the 1670s, it was observed that monia and methane in the spectra of Jupiter. [83] when Jupiter was on the opposite side of the Sun from Three long-lived anticyclonic features termed white ovals 8 CHAPTER 1. JUPITER

were observed in 1938. For several decades they re- missions mained as separate features in the atmosphere, sometimes approaching each other but never merging. Finally, two Beginning in 1973, several spacecraft have performed of the ovals merged in 1998, then absorbed the third in planetary flyby maneuvers that brought them within ob- 2000, becoming Oval BA.*[84] servation range of Jupiter. The Pioneer missions ob- tained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radi- 1.7.3 Radiotelescope research ation fields near the planet were much stronger than ex- pected, but both spacecraft managed to survive in that In 1955, and Kenneth detected environment. The trajectories of these spacecraft were bursts of radio signals coming from Jupiter at 22.2 used to refine the mass estimates of the Jovian system. MHz.*[30] The period of these bursts matched the ro- Radio by the planet resulted in better mea- tation of the planet, and they were also able to use this surements of Jupiter's diameter and the amount of polar information to refine the rotation rate. Radio bursts from flattening.*[21]*[94] Jupiter were found to come in two forms: long bursts (or Six years later, the Voyager missions vastly improved L-bursts) lasting up to several seconds, and short bursts the understanding of the Galilean moons and discovered (or S-bursts) that had a duration of less than a hundredth * Jupiter's rings. They also confirmed that the Great Red of a second. [85] Spot was anticyclonic. Comparison of images showed Scientists discovered that there were three forms of radio that the Red Spot had changed hue since the Pioneer mis- signals transmitted from Jupiter. sions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the • Decametric radio bursts (with a wavelength of tens process of erupting. As the spacecraft passed behind the of meters) vary with the rotation of Jupiter, and are planet, it observed flashes of lightning in the night side influenced by interaction of Io with Jupiter's mag- atmosphere.*[15]*[21] netic field.*[86] The next mission to encounter Jupiter, the solar • Decimetric radio emission (with wavelengths mea- probe, performed a flyby maneuver to attain a polar or- sured in centimeters) was first observed by Frank bit around the Sun. During this pass the spacecraft con- Drake and Hein Hvatum in 1959.*[30] The ori- ducted studies on Jupiter's magnetosphere. Since Ulysses gin of this signal was from a torus-shaped belt has no cameras, no images were taken. A second flyby around Jupiter's equator. This signal is caused by six years later was at a much greater distance.*[93] cyclotron radiation from electrons that are acceler- ated in Jupiter's magnetic field.*[87]

• Thermal radiation is produced by heat in the atmo- sphere of Jupiter.*[30]

1.7.4 Exploration with space probes

Main article:

Since 1973 a number of automated spacecraft have vis- ited Jupiter, most notably the , the first spacecraft to get close enough to Jupiter to send back revelations about the properties and phenomena of the Solar System's largest planet.*[88]*[89] Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in ve- locity of the spacecraft, or delta-v. Entering a Hohmann transfer orbit from Earth to Jupiter from low Earth or- Cassini views Jupiter and Io on January 1, 2001 bit requires a delta-v of 6.3 km/s*[90] which is compa- rable to the 9.7 km/s delta-v needed to reach low Earth In 2000, the Cassini probe, en route to Saturn, flew by orbit.*[91] Fortunately, gravity assists through planetary Jupiter and provided some of the highest-resolution im- flybys can be used to reduce the energy required to reach ages ever made of the planet. On December 19, 2000, the Jupiter, albeit at the cost of a significantly longer flight spacecraft captured an image of the moon , but duration.*[92] the resolution was too low to show surface details.*[95] 1.8. MOONS 9

The New Horizons probe, en route to Pluto, flew by times Earth normal, at a temperature of 153 °C).*[101] Jupiter for . Its closest approach was on It would have melted thereafter, and possibly vaporized. February 28, 2007.*[96] The probe's cameras measured The Galileo orbiter itself experienced a more rapid ver- plasma output from volcanoes on Io and studied all sion of the same fate when it was deliberately steered into four Galilean moons in detail, as well as making long- the planet on September 21, 2003, at a speed of over 50 distance observations of the outer moons Himalia and km/s, to avoid any possibility of it crashing into and pos- .*[97] Imaging of the Jovian system began Septem- sibly contaminating Europa—a moon which has been hy- ber 4, 2006.*[98]*[99] pothesized to have the possibility of harboring life.*[100] Data from this mission revealed that hydrogen composes Galileo mission up to 90% of Jupiter's atmosphere.*[26] The tempera- tures data recorded was more than 300 °C (>570 °F) Main article: Galileo (spacecraft) and the windspeed measured more than 644 kmph (>400 So far the only spacecraft to orbit Jupiter is the Galileo or- mph) before the probes vapourised.*[26]

Future probes

NASA has a mission underway to study Jupiter in detail from a . Named Juno, the spacecraft launched in August 2011, and will arrive in late 2016.*[102] The next planned mission to the Jovian system will be the 's Jupiter Explorer (JUICE), due to launch in 2022.*[103]

Canceled missions

Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. NASA's JIMO (Jupiter Icy Moons Orbiter) was can- celled in 2005.*[104] A subsequent proposal for a joint NASA/ESA mission, called EJSM/Laplace, was de- veloped with a provisional launch date around 2020. EJSM/Laplace would have consisted of the NASA- led Jupiter , and the ESA-led .*[105] However by April 2011, ESA had formally ended the partnership citing budget issues at NASA and the consequences on the mission timetable. Jupiter as seen by the space probe Cassini. Instead ESA planned to go ahead with a European- only mission to compete in its L1 selec- biter, which went into orbit around Jupiter on December tion.*[106] 7, 1995.*[26] It orbited the planet for over seven years, conducting multiple flybys of all the Galilean moons and Amalthea. The spacecraft also witnessed the impact of Shoemaker–Levy 9 as it approached Jupiter in 1.8 Moons 1994, giving a unique vantage point for the event. While the information gained about the Jovian system from Main article: Moons of Jupiter Galileo was extensive, its originally designed capacity was See also: Timeline of discovery of Solar System planets limited by the failed deployment of its high-gain radio and their moons transmitting antenna.*[100] A 340- atmospheric probe was released Jupiter has 67 natural satellites.*[107] Of these, 51 are from the spacecraft in July 1995, entering Jupiter's at- less than 10 kilometres in diameter and have only been mosphere on December 7.*[26] It parachuted through discovered since 1975. The four largest moons, visible 150 km (93 mi) of the atmosphere at speed of about from Earth with on a clear night, known as the 2,575 km/h (1600 mph)*[26] and collected data for 57.6 "Galilean moons", are Io, Europa, Ganymede and Cal- minutes before it was crushed by the pressure (about 23 listo. 10 CHAPTER 1. JUPITER

is seen most dramatically in the extraordinary volcanic activity of innermost Io (which is subject to the strongest tidal forces), and to a lesser in the geological youth of Europa's surface (indicating recent resurfacing of the moon's exterior).

1.8.2 Classification of moons

Jupiter with the Galilean moons. Seen from Earth at this point in their orbits, Europa appears closer to Jupiter than does Io. Jupiter's moon Europa. 1.8.1 Galilean moons Before the discoveries of the Voyager missions, Jupiter's Main article: Galilean moons moons were arranged neatly into four groups of four, The orbits of Io, Europa, and Ganymede, some of based on commonality of their . Since then, the large number of new small outer moons has complicated this picture. There are now thought to be six main groups, although some are more distinct than others. A basic sub-division is a grouping of the eight inner reg- ular moons, which have nearly circular orbits near the plane of Jupiter's equator and are believed to have formed with Jupiter. The remainder of the moons consist of an The Galilean moons. From left to right, in order of increasing unknown number of small irregular moons with ellipti- distance from Jupiter: Io, Europa, Ganymede, Callisto. cal and inclined orbits, which are believed to be captured or fragments of captured asteroids. Irregular the largest satellites in the Solar System, form a pattern moons that belong to a group share similar orbital ele- known as a Laplace resonance; for every four orbits that ments and thus may have a common origin, perhaps as a Io makes around Jupiter, Europa makes exactly two orbits larger moon or captured body that broke up.*[109]*[110] and Ganymede makes exactly one. This resonance causes the gravitational effects of the three large moons to dis- tort their orbits into elliptical shapes, since each moon receives an extra tug from its neighbors at the same point 1.9 Interaction with the Solar Sys- in every orbit it makes. The from Jupiter, on tem the other hand, works to circularize their orbits.*[108] The eccentricity of their orbits causes regular flexing of Along with the Sun, the gravitational influence of Jupiter the three moons' shapes, with Jupiter's gravity stretching has helped shape the Solar System. The orbits of most them out as they approach it and allowing them to spring of the system's planets lie closer to Jupiter's orbital plane back to more spherical shapes as they swing away. This than the Sun's equatorial plane (Mercury is the only planet tidal flexing heats the moons' interiors by friction. This that is closer to the Sun's equator in orbital tilt), the 1.9. INTERACTION WITH THE SOLAR SYSTEM 11

Kirkwood gaps in the belt are mostly caused by Jupiter, and the planet may have been responsible for the of the inner Solar System's history.*[112]

Hubble image taken on July 23 showing a blemish of about 5,000 miles long left by the 2009 Jupiter impact.*[115]

numbers that it accretes or ejects them.*[118] This topic This diagram shows the asteroids in Jupiter's orbit, as well remains controversial among astronomers, as some be- as the main . lieve it draws towards Earth from the belt Along with its moons, Jupiter's gravitational field con- while others believe that Jupiter protects Earth from the alleged .*[119] Jupiter experiences about 200 trols numerous asteroids that have settled into the re- * gions of the Lagrangian points preceding and following times more asteroid and comet impacts than Earth. [26] Jupiter in its orbit around the Sun. These are known A 1997 survey of historical astronomical drawings sug- as the Trojan asteroids, and are divided into Greek and gested that the astronomer Cassini may have recorded an Trojan “camps”to commemorate the Iliad. The first impact scar in 1690. The survey determined eight other of these, 588 Achilles, was discovered by Max Wolf in candidate observations had low or no possibilities of an 1906; since then more than two thousand have been dis- impact.*[120] A fireball was photographed by Voyager 1 covered.*[113] The largest is . during its Jupiter encounter in March 1979.*[121] During Most short-period comets belong to the Jupiter family the period July 16, 1994, to July 22, 1994, over 20 frag- —defined as comets with semi-major axes smaller than ments from the comet Shoemaker–Levy 9 (SL9, formally Jupiter's. Jupiter family comets are believed to form in designated D/1993 F2) collided with Jupiter's southern the outside the orbit of Neptune. During close hemisphere, providing the first direct observation of a encounters with Jupiter their orbits are perturbed into a collision between two Solar System objects. This impact provided useful data on the composition of Jupiter's at- smaller period and then circularized by regular gravita- * * tional interaction with the Sun and Jupiter.*[114] mosphere. [122] [123] On July 19, 2009, an impact site was discovered at approximately 216 degrees in System 1.9.1 Impacts 2.*[124]*[125] This impact left behind a spot in Jupiter's atmosphere, similar in size to Oval BA. Infrared See also: Comet Shoemaker–Levy 9, 2009 Jupiter im- observation showed a bright spot where the impact took pact event and 2010 Jupiter place, meaning the impact warmed up the lower atmo- Jupiter has been called the Solar System's sphere in the area near Jupiter's south pole.*[126] cleaner,*[116] because of its immense gravity well and location near the inner Solar System. It receives the A fireball, smaller than the previous observed impacts, most frequent comet impacts of the Solar System's plan- was detected on June 3, 2010, by Anthony Wesley, an ets.*[117] It was thought that the planet served to par- amateur astronomer in , and was later discov- ered to have been captured on video by another amateur tially shield the inner system from cometary bombard- * * astronomer in the Philippines. [127] Yet another fireball ment. [26] Recent computer simulations suggest that * Jupiter does not cause a net decrease in the number of was seen on August 20, 2010. [128] comets that pass through the inner Solar System, as its On September 10, 2012, another fireball was de- gravity perturbs their orbits inward in roughly the same tected.*[121]*[129] 12 CHAPTER 1. JUPITER

1.10 Possibility of life planet along the to define the of their zodiac.*[21]*[134] Further information: The Romans named it after Jupiter (Latin: Iuppiter, Iū- piter) (also called Jove), the principal god of Roman In 1953, the Miller–Urey experiment demonstrated that mythology, whose name comes from the Proto-Indo- a combination of lightning and the chemical compounds European vocative compound *Dyēu-pəter (nominative: that existed in the atmosphere of a primordial Earth could *Dyēus-pətēr, meaning “O Father Sky-God”, or “O * form organic compounds (including amino ) that Father -God”). [135] In turn, Jupiter was the coun- could serve as the building blocks of life. The simu- terpart to the mythical Greek (Ζεύς), also referred lated atmosphere included water, methane, ammonia and to as Dias (Δίας), the planetary name of which is retained * molecular hydrogen; all molecules still found in the at- in modern Greek. [136] mosphere of Jupiter. The atmosphere of Jupiter has a The astronomical symbol for the planet, , is a stylized strong vertical air circulation, which would carry these representation of the god's lightning bolt. The original compounds down into the lower regions. The higher tem- Greek deity Zeus supplies the root zeno-, used to form peratures within the interior of the atmosphere breaks some Jupiter-related words, such as zenographic.*[137] down these chemicals, which would hinder the formation of Earth-like life.*[130] Jovian is the adjectival form of Jupiter. The older adjec- tival form jovial, employed by astrologers in the Middle It is considered highly unlikely that there is any Earth- Ages, has come to mean “happy”or “merry,”moods like life on Jupiter, as there is only a small amount of wa- ascribed to Jupiter's astrological influence.*[138] ter in the atmosphere and any possible solid surface deep within Jupiter would be under extraordinary pressures. In The Chinese, Korean and Japanese referred to the planet as the “wood star”(Chinese: 木星; pinyin: mùxīng), 1976, before the Voyager missions, it was hypothesized * that ammonia or water-based life could evolve in Jupiter's based on the Chinese Five Elements. [139] Chinese Tao- upper atmosphere. This hypothesis is based on the ecol- ism personified it as the Fu star. The Greeks called “ ” ogy of terrestrial which have simple photosynthetic it Φαέθων, Phaethon, blazing. In Vedic , plankton at the top level, fish at lower levels feeding on Hindu astrologers named the planet after Brihaspati, the these creatures, and marine predators which hunt the religious teacher of the gods, and often called it "Guru", “ ”* fish.*[131]*[132] which literally means the Heavy One. [140] In the En- glish language, Thursday is derived from“'s day”, The possible presence of underground oceans on some of with Thor associated with the planet Jupiter in Germanic Jupiter's moons has led to speculation that the presence mythology.*[141] of life is more likely there. In the Central Asian-Turkic myths, Jupiter called as a “Erendiz/Erentüz”, which means“eren(?)+yultuz(star)". There are many theories about meaning of“eren”. Also, 1.11 Mythology these peoples calculated the period of the orbit of Jupiter as 11 years and 300 days. They believed that some social and natural events connected to Erentüz's movements on the sky.*[142]

1.12 See also

•

• Jovian–Plutonian gravitational effect

• Jovian (fiction)

Jupiter, woodcut from a 1550 edition of Guido Bonatti's Liber • Juno (spacecraft) Astronomiae. • The planet Jupiter has been known since ancient times. It Jupiter in fiction is visible to the in the night sky and can occa- sionally be seen in the daytime when the Sun is low.*[133] • To the Babylonians, this object represented their god Marduk. They used the roughly 12-year orbit of this • New Horizons 1.14. REFERENCES 13

1.13 Notes [11] De Crespigny, Rafe.“Emperor Huan and Emperor Ling” . Asian studies, Online Publications. Archived from the original on September 7, 2006. Retrieved May 1, 2012. [1] Orbital elements refer to the barycenter of the Jupiter sys- Xu Huang apparently complained that the astronomy of- tem, and are the instantaneous osculating values at the fice had failed to give them proper emphasis to the precise J2000 . Barycenter quantities are given be- and to other portents, including the movement of the cause, in contrast to the planetary centre, they do not ex- planet Jupiter (taisui). At his instigation, Chen Shou/Yuan perience appreciable changes on a day-to-day basis due to was summoned and questioned, and it was under this pres- the motion of the moons. sure that his advice implicated Liang Ji. [2] Refers to the level of 1 bar atmospheric pressure [12] Stuart Taylor (2001). Solar system evolution: a new perspective : an inquiry into the chemical composition, ori- gin, and evolution of the solar system (2nd, illus., revised 1.14 References ed.). Cambridge University Press. p. 208. ISBN 0-521- 64130-6.

[1] Jupiter, entry in the Oxford English Dictionary, prepared [13] “Young astronomer captures a shadow cast by Jupiter: by J. A. Simpson and E. S. C. Weiner, vol. 8, second Bad Astronomy”. Blogs.discovermagazine.com. Novem- edition, Oxford: Clarendon Press, 1989. ISBN 0-19- ber 18, 2011. Retrieved May 27, 2013. 861220-6 (vol. 8), ISBN 0-19-861186-2 (set.) [14] Saumon, D.; Guillot, T. (2004). “Shock Compression of [2] Yeomans, Donald K. (July 13, 2006). “HORIZONS and the Interiors of Jupiter and Saturn”. The Web-Interface for Jupiter Barycenter (Major Body=5)". Astrophysical Journal 609 (2): 1170–1180. arXiv:astro- JPL Horizons On-Line System. Retrieved Au- /0403393. :2004ApJ...609.1170S. gust 8, 2007. – Select “Ephemeris Type: Orbital Ele- doi:10.1086/421257. ments”, “Time Span: January 1, 2000 12:00 to 2000- 01-02”.(“Target Body: Jupiter Barycenter”and“Center: [15] Gautier, D.; Conrath, B.; Flasar, M.; Hanel, R.; Sun”should be defaulted to.) Kunde, V.; Chedin, A.; Scott N. (1981). “The helium abundance of Jupiter from Voyager” [3] Seligman, . “Rotation Period and Day Length” . Journal of Geophysical Research 86 (A10): . Retrieved August 13, 2009. 8713–8720. Bibcode:1981JGR....86.8713G. doi:10.1029/JA086iA10p08713. [4] Williams, Dr. R. (November 16, 2004). “Jupiter Fact Sheet”. NASA. Retrieved August 8, 2007. [16] Kunde, V. G. et al. (September 10, 2004). “Jupiter's Atmospheric Composition from the Cassini [5] “The MeanPlane (Invariable plane) of the Solar System Thermal Infrared Spectroscopy Experiment”. Science passing through the barycenter”. April 3, 2009. Retrieved 305 (5690): 1582–86. Bibcode:2004Sci...305.1582K. April 10, 2009. (produced with Solex 10 written by Aldo doi:10.1126/science.1100240. PMID 15319491. Re- Vitagliano; see also Invariable plane) trieved April 4, 2007.

[6] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, [17] Kim, S. J.; Caldwell, J.; Rivolo, A. R.; Wagner, R. Michael F. et al. (2007). “Report of the IAU/IAG (1985). “Infrared Polar Brightening on Jupiter III. Working Group on cartographic coordinates and Spectrometry from the Voyager 1 Experiment”. rotational elements: 2006”. Celestial Mechan- Icarus 64 (2): 233–48. Bibcode:1985Icar...64..233K. ics and Dynamical Astronomy 98 (3): 155–180. doi:10.1016/0019-1035(85)90201-5. Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- 007-9072-y. [18] Niemann, H. B.; Atreya, S. K.; Carignan, G. R.; Don- ahue, T. M.; Haberman, J. A.; Harpold, D. N.; Har- [7] “Solar System Exploration: Jupiter: Facts & Figures”. tle, R. E.; Hunten, D. M.; Kasprzak, W. T.; Ma- NASA. May 7, 2008. haffy, P. R.; Owen, T. C.; Spencer, N. W.; Way, S. H. (1996). “The Galileo Probe Mass Spectrome- [8]“Astrodynamic Constants”. JPL Solar System Dynamics. ter: Composition of Jupiter's Atmosphere”. Science February 27, 2009. Retrieved August 8, 2007. 272 (5263): 846–849. Bibcode:1996Sci...272..846N. doi:10.1126/science.272.5263.846. PMID 8629016. [9] Seidelmann, P. K.; Abalakin, V. K.; Bursa, M.; , M. E.; de Burgh, C.; Lieske, J. H.; Oberst, J.; Simon, J. [19] von Zahn, U.; Hunten, D. M.; Lehmacher, G. (1998). L.; Standish, E. M.; Stooke, P.; Thomas, P. C. (2001). “Helium in Jupiter's atmosphere: Results from the Galileo “Report of the IAU/IAG Working Group on Cartographic probe Helium Interferometer Experiment”. Journal Coordinates and Rotational Elements of the Planets and of Geophysical Research 103 (E10): 22815–22829. Satellites: 2000”. HNSKY Program. Re- doi:10.1029/98JE00695. trieved February 2, 2007. [20] Ingersoll, A. P.; Hammel, H. B.; Spilker, T. R.; Young, [10] Anonymous (March 1983). “Probe Nephelometer”. R. E. (June 1, 2005). “Outer Planets: The Ice Giants” Galileo Messenger (NASA/JPL) (6). Retrieved February (PDF). Lunar & Planetary Institute. Retrieved February 12, 2007. 1, 2007. 14 CHAPTER 1. JUPITER

[21] Burgess, Eric (1982). By Jupiter: Odysseys to a Giant. [35] Horia, Yasunori; Sanoa, ; Ikomaa, Masahiro; New York: Columbia University Press. ISBN 0-231- Idaa, Shigeru (2007). “On uncertainty of Jupiter's 05176-X. core mass due to observational errors”. Pro- ceedings of the International Astronomical Union [22] Shu, Frank H. (1982). The physical : an intro- (Cambridge University Press) 3 (S249): 163–166. duction to astronomy. Series of books in astronomy (12th doi:10.1017/S1743921308016554. ed.). University Science Books. p. 426. ISBN 0-935702- 05-9. [36] Lodders, Katharina (2004). “Jupiter Formed with More Tar than Ice”. The Astrophysical Journal [23] Davis, Andrew M.; Turekian, Karl K. (2005). , 611 (1): 587–597. Bibcode:2004ApJ...611..587L. comets, and planets. Treatise on 1. Elsevier. doi:10.1086/421970. Retrieved July 3, 2007. p. 624. ISBN 0-08-044720-1. [37] Züttel, Andreas (September 2003). “Materials for [24] Jean Schneider (2009). “The Extrasolar Planets Ency- hydrogen storage”. Materials Today 6 (9): 24–33. clopedia: Interactive Catalogue”. Observatory. doi:10.1016/S1369-7021(03)00922-2.

[25] Seager, S.; Kuchner, M.; Hier-Majumder, C. A.; Mil- [38] Guillot, T. (1999). “A comparison of the interiors itzer, B. (2007). “Mass-Radius Relationships for Solid of Jupiter and Saturn”. Planetary and Space Science ”. The Astrophysical Journal 669 (2): 1279– 47 (10–11): 1183–200. arXiv:astro-ph/9907402. 1297. arXiv:0707.2895. Bibcode:2007ApJ...669.1279S. Bibcode:1999P&SS...47.1183G. doi:10.1016/S0032- doi:10.1086/521346. 0633(99)00043-4.

[26] How the Universe Works 3. Jupiter: Destroyer or Savior?. [39] Lang, Kenneth R. (2003). “Jupiter: a giant primitive Discovery Channel. 2014. planet”. NASA. Retrieved January 10, 2007.

[27] Guillot, Tristan (1999). “Interiors of Giant Plan- [40] Seiff, A.; Kirk, D.B.; Knight, T.C.D. et al. (1998). ets Inside and Outside the Solar System”. Sci- “Thermal structure of Jupiter's atmosphere near ence 286 (5437): 72–77. Bibcode:1999Sci...286...72G. the edge of a 5-μm hot spot in the north equato- doi:10.1126/science.286.5437.72. PMID 10506563. Re- rial belt”. Journal of Geophysical Research 103 trieved August 28, 2007. (E10): 22857–22889. Bibcode:1998JGR...10322857S. doi:10.1029/98JE01766. [28] Burrows, A.; Hubbard, W. B.; Saumon, D.; Lunine, J. I. (1993). “An expanded set of and very low [41] Miller, Steve; Aylward, Alan; Millward, George mass star models”. Astrophysical Journal 406 (1): 158– (January 2005). “Giant Planet and 71. Bibcode:1993ApJ...406..158B. doi:10.1086/172427. Thermospheres: The Importance of Ion-Neutral Cou- pling”. Space Science Reviews 116 (1–2): 319–343. [29] Queloz, Didier (November 19, 2002). “VLT Interfer- Bibcode:2005SSRv..116..319M. doi:10.1007/s11214- ometer Measures the Size of Proxima Centauri and Other 005-1960-4. Nearby Stars”. European Southern Observatory. Re- trieved January 12, 2007. [42] Ingersoll, A. P.; Dowling, T. E.; Gierasch, P. J.; Orton, G. S.; Read, P. L.; Sanchez-Lavega, A.; Showman, A. [30] Elkins-Tanton, Linda T. (2006). Jupiter and Saturn. New P.; Simon-Miller, A. A.; Vasavada, A. R. “Dynamics of York: Chelsea . ISBN 0-8160-5196-8. Jupiter's Atmosphere” (PDF). Lunar & Planetary Insti- tute. Retrieved February 1, 2007. [31] Guillot, T.; Stevenson, D. J.; Hubbard, W. B.; Saumon, D. (2004). “Chapter 3: The Interior of Jupiter”. In Bage- [43] Watanabe, Susan, ed. (February 25, 2006). “Surprising nal, F.; Dowling, T. E.; McKinnon, W. B. Jupiter: The Jupiter: Busy Galileo spacecraft showed jovian system is Planet, Satellites and Magnetosphere. Cambridge Univer- full of surprises”. NASA. Retrieved February 20, 2007. sity Press. ISBN 0-521-81808-7. [44] Kerr, Richard A. (2000). “Deep, Moist Heat Drives [32] Bodenheimer, P. (1974). “Calculations of the early Jovian ”. Science 287 (5455): 946–947. evolution of Jupiter”. Icarus. 23 23 (3): 319– doi:10.1126/science.287.5455.946b. Retrieved February 25. Bibcode:1974Icar...23..319B. doi:10.1016/0019- 24, 2007. 1035(74)90050-5. [45] Strycker, P. D.; Chanover, N.; Sussman, M.; Simon- [33] Guillot, T.; Gautier, D.; Hubbard, W. B. (1997). Miller, A. (2006). A Spectroscopic Search for Jupiter's “New Constraints on the Composition of Jupiter Chromophores. DPS meeting #38, #11.15 (American As- from Galileo Measurements and Interior Mod- tronomical Society). Bibcode:2006DPS....38.1115S. els”. Icarus 130 (2): 534–539. arXiv:astro- ph/9707210. Bibcode:1997astro.ph..7210G. [46] Gierasch, Peter J.; Nicholson, Philip D. (2004).“Jupiter” doi:10.1006/icar.1997.5812. . World Book @ NASA. Retrieved August 10, 2006.

[34] Various (2006). McFadden, -Ann; Weissman, Paul; [47] Harrington, J.D.; Weaver, ; Villard, Ray (May Johnson, Torrence, eds. Encyclopedia of the Solar System 15, 2014). “Release 14-135 – NASA's Hubble Shows (2nd ed.). Academic Press. p. 412. ISBN 0-12-088589- Jupiter's Great Red Spot is Smaller than Ever Measured” 1. . NASA. Retrieved May 16, 2014. 1.14. REFERENCES 15

[48]“HubbleSite- NewsCenter”. NASA. Retrieved December [65] Herbst, T. M.; Rix, H.-W. (1999). Guenther, Eike; 12, 2013. Stecklum, Bringfried; Klose, Sylvio, eds. Star Forma- tion and Extrasolar Planet Studies with Near-Infrared In- [49] , W. F. (1899).“Jupiter, early history of the great terferometry on the LBT 188. San , Calif.: red spot on”. Monthly Notices of the Royal Astronomical Astronomical Society of the Pacific. pp. 341–350. Society 59: 574–584. Bibcode:1899MNRAS..59..574D. Bibcode:1999ASPC..188..341H. ISBN 1-58381-014-5. [50] Kyrala, A. (1982). “An explanation of the persistence – See section 3.4. of the Great Red Spot of Jupiter”. Moon and the [66] Michtchenko, T. A.; Ferraz-Mello, S. (February Planets 26 (1): 105–7. Bibcode:1982M&P....26..105K. 2001). “Modeling the 5 : 2 Mean-Motion Resonance doi:10.1007/BF00941374. in the Jupiter–Saturn ”. Icarus [51] Philosophical Transactions Vol. I (1665–1666.). Project 149 (2): 77–115. Bibcode:2001Icar..149..357M. Gutenberg. Retrieved on December 22, 2011. doi:10.1006/icar.2000.6539.

[52] Sommeria, Jöel; Meyers, Steven D.; Swinney, Harry [67] “Interplanetary Seasons”. Science@NASA. Retrieved L. (February 25, 1988). “Laboratory simulation of February 20, 2007. Jupiter's Great Red Spot”. 331 (6158): 689–693. Bibcode:1988Natur.331..689S. doi:10.1038/331689a0. [68] Ridpath, Ian (1998). Norton's Star (19th ed.). Pren- tice Hall. ISBN 0-582-35655-5. [53] Covington, Michael A. (2002). Celestial Objects for Mod- ern Telescopes. Cambridge University Press. p. 53. ISBN [69] Horizons output. “Favorable Appearances by Jupiter”. 0-521-52419-9. Retrieved January 2, 2008. (Horizons)

[54] Cardall, C. Y.; Daunt, S. J.“The Great Red Spot”. Uni- [70] “Encounter with the Giant”. NASA. 1974. Retrieved versity of Tennessee. Retrieved February 2, 2007. February 17, 2007.

[55] “Jupiter Data Sheet”. Space.com. Retrieved February [71] “How to Observe Jupiter”. WikiHow. July 28, 2013. 2, 2007. Retrieved July 28, 2013.

[56] Phillips, Tony (March 3, 2006).“Jupiter's New Red Spot” [72] A. Sachs (May 2, 1974). “Babylonian Observational As- . NASA. Retrieved February 2, 2007. tronomy”. Philosophical Transactions of the Royal So- ciety of London (Royal Society of London) 276 (1257): [57] “Jupiter's New Red Spot”. 2006. Retrieved March 9, 43–50 (see p. 44). Bibcode:1974RSPTA.276...43S. 2006. doi:10.1098/rsta.1974.0008. JSTOR 74273. [58] Steigerwald, Bill (October 14, 2006).“Jupiter's Little Red “ Spot Growing Stronger”. NASA. Retrieved February 2, [73] Xi, Z. Z. (1981). The Discovery of Jupiter's 2007. Satellite Made by Gan-De 2000 Years Before Galileo”. Acta Astrophysica Sinica 1 (2): 87. [59] Goudarzi, Sara (May 4, 2006). “New storm on Jupiter Bibcode:1981AcApS...1...87X. hints at climate changes”. USA Today. Retrieved Febru- ary 2, 2007. [74] Dong, Paul (2002). China's Major Mysteries: Paranormal Phenomena and the Unexplained in the People's Republic. [60] Showalter, M.A.; , J.A.; Cuzzi, J. N.; , China Books. ISBN 0-8351-2676-5. J. B. (1987). “Jupiter's ring system: New results on structure and particle properties”. Icarus 69 (3): 458– [75] Olaf Pedersen (1974). A Survey of the Almagest. Odense 98. Bibcode:1987Icar...69..458S. doi:10.1016/0019- University Press. pp. 423, 428. 1035(87)90018-2. [76] tr. with notes by Walter Eugene (1930). The Aryab- [61] Burns, J. A.; Showalter, M.R.; Hamilton, hatiya of Aryabhata. University of Chicago Press. p. 9, D.P. et al. (1999). “The Formation of Stanza 1. Jupiter's Faint Rings”. Science 284 (5417): 1146–50. Bibcode:1999Sci...284.1146B. [77] Westfall, Richard S. “Galilei, Galileo”. The Galileo doi:10.1126/science.284.5417.1146. PMID 10325220. Project. Retrieved January 10, 2007.

[62] Fieseler, P.D.; , Olen W; Vandermey, Nancy; [78] Murdin, Paul (2000). Encyclopedia of Astronomy and As- Theilig, E.E; Schimmels, Kathryn A; Lewis, George trophysics. Bristol: Institute of Physics Publishing. ISBN D; Ardalan, Shadan M; , Claudia J (2004). 0-12-226690-0. “The Galileo Star Scanner Observations at Amalthea”. Icarus 169 (2): 390–401. Bibcode:2004Icar..169..390F. [79] “SP-349/396 Pioneer Odyssey—Jupiter, Giant of the So- doi:10.1016/j.icarus.2004.01.012. lar System”. NASA. August 1974. Retrieved August 10, 2006. [63] Brainerd, Jim (November 22, 2004).“Jupiter's Magneto- sphere”. The Spectator. Retrieved August [80] “Roemer's Hypothesis”. MathPages. Retrieved January 10, 2008. 12, 2007.

[64] “Radio Storms on Jupiter”. NASA. February 20, 2004. [81] Tenn, Joe (March 10, 2006).“” Retrieved February 1, 2007. . Sonoma State University. Retrieved January 10, 2007. 16 CHAPTER 1. JUPITER

[82] “Amalthea Fact Sheet”. NASA JPL. October 1, 2001. [99] Alexander, Amir (September 27, 2006).“New Horizons Retrieved February 21, 2007. Snaps First Picture of Jupiter”. The Planetary Society. Archived from the original on February 21, 2007. Re- [83] Dunham Jr., Theodore (1933). “Note on the trieved December 19, 2006. Spectra of Jupiter and Saturn”. Publications of the Astronomical Society of the Pacific 45: 42–44. [100] McConnell, Shannon (April 14, 2003).“Galileo: Journey Bibcode:1933PASP...45...42D. doi:10.1086/124297. to Jupiter”. NASA Jet Propulsion Laboratory. Retrieved November 28, 2006. [84] Youssef, A.; Marcus, P. S. (2003). “The dynam- ics of jovian white ovals from formation to merger”. [101] Magalhães, Julio (December 10, 1996). “Galileo Probe Icarus 162 (1): 74–93. Bibcode:2003Icar..162...74Y. Mission Events”. NASA Space Projects Division. Re- doi:10.1016/S0019-1035(02)00060-X. trieved February 2, 2007. [102] Goodeill, Anthony (March 31, 2008). “New Frontiers – [85] Weintraub, Rachel A. (September 26, 2005). “How One Missions – Juno”. NASA. Retrieved January 2, 2007. Night in a Field Changed Astronomy”. NASA. Retrieved February 18, 2007. [103] Amos, Jonathan (May 2, 2012). “Esa selects 1bn-euro Juice probe to Jupiter”. BBC News Online. Retrieved [86] Garcia, Leonard N.“The Jovian Decametric Radio - May 2, 2012. sion”. NASA. Retrieved February 18, 2007. [104] Berger, Brian (February 7, 2005). “White House scales [87] Klein, M. J.; Gulkis, S.; Bolton, S. J. (1996). “Jupiter's back space plans”. MSNBC. Retrieved January 2, 2007. Synchrotron Radiation: Observed Variations Before, During and After the Impacts of Comet SL9”. NASA. [105] “Laplace: A mission to Europa & Jupiter system”. ESA. Retrieved February 18, 2007. Retrieved January 23, 2009.

[88] NASA – Pioneer 10 Mission Profile. NASA. Retrieved [106] New approach for L-class mission candidates, ESA, April on December 22, 2011. 19, 2011

[89] NASA – . NASA. Retrieved on [107] Sheppard, Scott S. “The Giant Planet Satellite and December 22, 2011. Moon Page”. Departament of Terrestrial at Carniege Institution for science. Retrieved December 19, [90] Fortescue, Peter W.; Stark, John and Swinerd, Graham 2014. Spacecraft systems engineering, 3rd ed., John Wiley and [108] Musotto, S.; Varadi, F.; Moore, W. B.; Schu- Sons, 2003, ISBN 0-470-85102-3 p. 150. bert, G. (2002). “Numerical simulations of the [91] Hirata, Chris.“Delta-V in the Solar System”. California orbits of the Galilean satellites”. Icarus 159 Institute of Technology. Archived from the original on (2): 500–504. Bibcode:2002Icar..159..500M. July 15, 2006. Retrieved November 28, 2006. doi:10.1006/icar.2002.6939. [109] Jewitt, D. C.; Sheppard, S.; Porco, C. (2004). Bagenal, [92] Wong, Al (May 28, 1998). “Galileo FAQ: Navigation” F.; Dowling, T.; McKinnon, W, eds. Jupiter: The Planet, . NASA. Retrieved November 28, 2006. Satellites and Magnetosphere (PDF). Cambridge Univer- [93] Chan, K.; Paredes, E. S.; Ryne, M. S. (2004). “Ulysses sity Press. ISBN 0-521-81808-7. Archived from the orig- Attitude and Orbit Operations: 13+ Years of International inal on July 14, 2011. Cooperation”. American Institute of Aeronautics and As- [110] Nesvorný, D.; Alvarellos, J. L. A.; Dones, L.; Levi- tronautics. Retrieved November 28, 2006. son, H. F. (2003). “Orbital and Collisional Evolution of the Irregular Satellites”. The Astronomical Jour- [94] Lasher, Lawrence (August 1, 2006). “Pioneer Project nal 126 (1): 398–429. Bibcode:2003AJ....126..398N. Home Page”. NASA Space Projects Division. Retrieved doi:10.1086/375461. November 28, 2006. [111] Showman, A. P.; Malhotra, R. (1999). “The [95] Hansen, C. J.; Bolton, S. J.; Matson, D. L.; Galilean Satellites”. Science 286 (5437): 77–84. Spilker, L. J.; Lebreton, J.-P. (2004). “The doi:10.1126/science.286.5437.77. PMID 10506564. Cassini– flyby of Jupiter”. Icarus 172 (1): 1–8. Bibcode:2004Icar..172....1H. [112] Kerr, Richard A. (2004). “Did Jupiter and Saturn doi:10.1016/j.icarus.2004.06.018. Team Up to Pummel the Inner Solar System?". Science 306 (5702): 1676. doi:10.1126/science.306.5702.1676a. [96] “Mission Update: At Closest Approach, a Fresh View of PMID 15576586. Retrieved August 28, 2007. Jupiter”. Archived from the original on April 29, 2007. Retrieved July 27, 2007. [113] “List Of Jupiter Trojans”. IAU Center. Retrieved October 24, 2010. [97] “Pluto-Bound New Horizons Provides New Look at Jupiter System”. Retrieved July 27, 2007. [114] Quinn, T.; Tremaine, S.; Duncan, M. (1990). “Plan- etary perturbations and the origins of short-period [98] “New Horizons targets Jupiter kick”. BBC News Online. comets”. Astrophysical Journal, Part 1 355: 667–679. January 19, 2007. Retrieved January 20, 2007. Bibcode:1990ApJ...355..667Q. doi:10.1086/168800. 1.14. REFERENCES 17

[115] Dennis Overbye (July 24, 2009).“Hubble Takes Snapshot [130] Heppenheimer, T. A. (2007).“Colonies in Space, Chap- of Jupiter's 'Black Eye'". New York Times. Retrieved July ter 1: Other Life in Space”. National Space Society. 25, 2009. Retrieved February 26, 2007.

[116] Lovett, Richard A. (December 15, 2006). “'s [131] “Life on Jupiter”. Encyclopedia of , As- Comet Clues Reveal Early Solar System”. National Ge- tronomy & Spaceflight. Retrieved March 9, 2006. ographic News. Retrieved January 8, 2007. [132] , C.; Salpeter, E. E. (1976). “Particles, environ- [117] Nakamura, T.; Kurahashi, H. (1998). “Colli- ments, and possible ecologies in the Jovian atmosphere”. sional Probability of Periodic Comets with the Ter- The Astrophysical Journal Supplement Series 32: 633–637. restrial Planets: An Invalid Case of Analytic Formu- Bibcode:1976ApJS...32..737S. doi:10.1086/190414. lation”. Astronomical Journal 115 (2): 848–854. Bibcode:1998AJ....115..848N. doi:10.1086/300206. Re- “ trieved August 28, 2007. [133] Staff (June 16, 2005). Stargazers prepare for daylight view of Jupiter”. ABC News Online. Archived from the [118] Horner, J.; , B. W. (2008). “Jupiter original on May 12, 2011. Retrieved February 28, 2008. – friend or foe? I: the asteroids.”. Interna- tional Journal of Astrobiology 7 (3–4): 251–261. [134] Rogers, J. H. (1998). “Origins of the ancient con- arXiv:0806.2795. Bibcode:2008IJAsB...7..251H. stellations: I. The Mesopotamian traditions”. Jour- doi:10.1017/S1473550408004187. nal of the British Astronomical Association 108: 9–28. Bibcode:1998JBAA..108....9R. [119] Overbyte, Dennis (July 25, 2009). “Jupiter: Our Comic Protector?". Thew New York Times. Retrieved July 27, [135] Harper, Douglas (November 2001). “Jupiter”. Online 2009. Etymology Dictionary. Retrieved February 23, 2007. [120] Tabe, Isshi; Watanabe, Jun-ichi; Jimbo, Michiwo [136] “Greek Names of the Planets”. Retrieved July 14, 2012. (February 1997). “Discovery of a Possible Impact In Greek the name of the planet Jupiter is Dias, the Greek SPOT on Jupiter Recorded in 1690”. Publications name of god Zeus. See also the Greek article about the of the Astronomical Society of Japan 49: L1–L5. planet. Bibcode:1997PASJ...49L...1T. doi:10.1093/pasj/49.1.l1.

[121] Marchis (September 10, 2012).“Another fireball [137] See for example:“IAUC 2844: Jupiter; 1975h”. Interna- on Jupiter? .”. Cosmic Diary blog. Retrieved September tional Astronomical Union. October 1, 1975. Retrieved 11, 2012. October 24, 2010. That particular word has been in use since at least 1966. See: “Query Results from the As- [122] Baalke, Ron. “Comet Shoemaker-Levy Collision with tronomy Database”. Smithsonian/NASA. Retrieved July Jupiter”. NASA. Retrieved January 2, 2007. 29, 2007.

“ [123] Britt, Robert R. (August 23, 2004). Remnants of 1994 [138] “Jovial”. Dictionary.com. Retrieved July 29, 2007. Comet Impact Leave Puzzle at Jupiter”. space.com. Re- trieved February 20, 2007. [139] ‹The template Chinaplanetnames is being considered for [124] Staff (July 21, 2009). “Amateur astronomer discovers deletion.› Jupiter collision”. ABC News online. Retrieved July 21, China: De Groot, Jan Jakob Maria (1912). Religion in 2009. China: universism. a key to the study of Taoism and Con- fucianism. American lectures on the history of religions 10 [125] Salway, Mike (July 19, 2009). “Breaking News: Pos- (G. P. Putnam's Sons). p. 300. Retrieved 2010-01-08. sible Impact on Jupiter, Captured by Anthony Wesley”. Japan: Crump, Thomas (1992). The Japanese numbers IceInSpace. IceInSpace News. Retrieved July 19, 2009. game: the use and understanding of numbers in modern Japan. Nissan Institute/Routledge Japanese studies series [126] Grossman, Lisa (July 20, 2009). “Jupiter sports new (Routledge). pp. 39–40. ISBN 0415056098. 'bruise' from impact”. New Scientist. Korea: Hulbert, Bezaleel (1909). The passing of Korea. Doubleday, Page & company. p. 426. Retrieved “ [127] Bakich, Michael (June 4, 2010). Another impact on 2010-01-08. Jupiter”. Astronomy Magazine online. Retrieved June 4, 2010. [140] “Guru”. Indian Divinity.com. Retrieved February 14, [128] Beatty, Kelly (August 22, 2010). “Another Flash on 2007. Jupiter!". Sky & Telescope. Sky Publishing. Archived from the original on August 27, 2010. Retrieved August [141] Falk, Michael; Koresko, Christopher (1999). “As- 23, 2010. Masayuki Tachikawa was observing ... 18:22 tronomical Names for the Days of the ” Universal Time on the 20th ... Kazuo Aoki posted an im- . Journal of the Royal Astronomical Society of age ... Ishimaru of Toyama prefecture observed the event Canada 93: 122–33. Bibcode:1999JRASC..93..122F. doi:10.1016/j.newast.2003.07.002. [129] Hall, George (September 2012).“George's Astrophotog- raphy”. Retrieved September 17, 2012. 10 Sept. 2012 [142] “Türk Astrolojisi”. ntvmsnbc.com. Retrieved April 23, 11:35 UT .. observed by Dan Petersen 2010. 18 CHAPTER 1. JUPITER

1.15 Further reading

• Bagenal, F.; Dowling, T. E.; McKinnon, W. B., eds. (2004). Jupiter: The planet, satellites, and magne- tosphere. Cambridge: Cambridge University Press. ISBN 0-521-81808-7. • Beebe, Reta (1997). Jupiter: The Giant Planet (Sec- ond ed.). Washington, D.C.: Smithsonian Institu- tion Press. ISBN 1-56098-731-6.

1.16 External links

• Hans Lohninger et al. (November 2, 2005). “Jupiter, As Seen By Voyager 1”. A Trip into Space. Virtual Institute of Applied Science. Re- trieved March 9, 2007. • Dunn, Tony (2006).“The Jovian System”. Gravity Simulator. Retrieved March 9, 2007.—A simulation of the 62 Jovian moons.

• Seronik, G.; Ashford, A. R. “Chasing the Moons of Jupiter”. Sky & Telescope. Archived from the original on July 13, 2007. Retrieved March 9, 2007. • Anonymous (May 2, 2007). “In Pictures: New views of Jupiter”. BBC News. Retrieved May 2, 2007.

• Cain, Fraser.“Jupiter”. Universe Today. Retrieved April 1, 2008.

• “Fantastic Flyby of the New Horizons spacecraft (May 1, 2007.)". NASA. Retrieved May 21, 2008. • “Moons of Jupiter articles in Re- search Discoveries”. Planetary Science Research Discoveries. University of Hawaii, NASA.

• June 2010 impact video • Bauer, Amanda; Merrifield, Michael (2009). “Jupiter”. Sixty Symbols. Brady Haran for the University of Nottingham. Chapter 2

Mars

This article is about the planet. For other uses, see Mars and the . Defunct (disambiguation). spacecraft on the surface include MER-A and sev- eral other inert landers and rovers such as the Mars is the fourth planet from the Sun and the sec- , which completed its mission in 2008. Observa- ond smallest planet in the Solar System, after Mercury. tions by the Mars Reconnaissance Orbiter have revealed possible flowing water during the warmest on Named after the Roman god of war, it is often referred * to as the “Red Planet”because the oxide prevalent Mars. [26] In 2013, NASA's Curiosity rover discovered on its surface gives it a reddish appearance.*[15] Mars that Mars's soil contains between 1.5% and 3% water by is a with a thin atmosphere, having sur- mass (about two pints of water per cubic foot or 33 liters per cubic meter, albeit attached to other compounds and face features reminiscent both of the impact craters of * the Moon and the volcanoes, valleys, deserts, and polar thus not freely accessible). [27] ice caps of Earth. The rotational period and seasonal cy- Mars can easily be seen from Earth with the naked eye, as cles of Mars are likewise similar to those of Earth, as can its reddish coloring. Its reaches is the tilt that produces the seasons. Mars is the site of −3.0,*[10] which is surpassed only by Jupiter, Venus, the , largest *[16] and second-highest Moon, and the Sun. Optical ground-based telescopes are known mountain in the Solar System and the tallest on typically limited to resolving features about 300 kilome- a planet, and of , one of the largest ters (190 mi) across when Earth and Mars are closest be- in the Solar System. The smooth Borealis basin cause of Earth's atmosphere.*[28] in the northern hemisphere covers 40% of the planet and may be a giant impact feature.*[17]*[18] Mars has two moons, and , which are small and irregu- larly shaped. These may be captured asteroids,*[19]*[20] 2.1 Physical characteristics similar to , a . Until the first successful Mars flyby in 1965 by 4, many speculated about the presence of liquid water on the planet's surface. This was based on observed peri- odic variations in light and dark patches, particularly in the polar latitudes, which appeared to be seas and conti- nents; long, dark striations were interpreted by some as irrigation channels for liquid water. These straight line Earth compared with Mars. features were later explained as optical illusions, though geological evidence gathered by unmanned missions sug- gests that Mars once had large-scale water coverage on its surface at some earlier stage of its life.*[21] In 2005, radar data revealed the presence of large quantities of wa- * * * ter ice at the poles [22] and at mid-latitudes. [23] [24] Mars - animation (00:40) showing major features. The Spirit sampled chemical compounds con- taining water molecules in March 2007. The Phoenix lan- der directly sampled water ice in shallow on Mars has approximately half the diameter of Earth. It is July 31, 2008.*[25] less dense than Earth, having about 15% of Earth's vol- ume and 11% of the mass. Its surface area is only slightly Mars is host to seven functioning spacecraft: five in or- less than the total area of Earth's dry land.*[6] Although — bit , , Mars Reconnais- Mars is larger and more massive than Mercury, Mercury — sance Orbiter, MAVEN and Mars Orbiter Mission and has a higher density. This results in the hav- — two on the surface ing a nearly identical gravitational pull at the surface—

19 20 CHAPTER 2. MARS

that of Mars is stronger by less than 1%. The red-orange appearance of the is caused by iron(III) oxide, more commonly known as , or rust.*[29] It can also look like butterscotch,*[30] and other common surface colors include golden, brown, tan, and greenish, depending on .*[30]

2.1.1 Internal structure

Like Earth, Mars has differentiated into a dense metallic core overlaid by less dense materials.*[31] Current mod- els of its interior imply a core region about 1,794 ± 65 kilometers (1,115 ± 40 mi) in radius, consisting primar- ily of iron and with about 16–17% sulfur.*[32] This iron(II) sulfide core is thought to be twice as rich in lighter elements than Earth's core.*[33] The core is surrounded by a that formed many of the tectonic and volcanic features on the planet, but it now appears to be dormant. Besides silicon and oxygen, the most abundant elements in the Martian are iron, , aluminum, , and . The av- Geologic Map of Mars (USGS; July 14, 2014) * * * erage thickness of the planet's crust is about 50 km (31 (full map / video) [39] [40] [41] mi), with a maximum thickness of 125 km (78 mi).*[33] Earth's crust, averaging 40 km (25 mi), is only one third that these bands demonstrate on Mars four as thick as Mars's crust, relative to the sizes of the two billion years ago, before the planetary dynamo ceased to planets. The InSight lander planned for 2016 will use a function and the planet's magnetic field faded away.*[43] seismometer to better constrain the models of the inte- rior.*[34] During the Solar System's formation, Mars was created as the result of a stochastic process of run-away out of the that orbited the Sun. Mars 2.1.2 Surface geology has many distinctive chemical features caused by its po- sition in the Solar System. Elements with comparatively Main article: low boiling points, such as , phosphorus, and sul- phur, are much more common on Mars than Earth; these elements were probably removed from areas closer to the Mars is a terrestrial planet that consists of minerals con- Sun by the young star's energetic solar wind.*[44] taining silicon and oxygen, metals, and other elements that typically make up . The surface of Mars is After the formation of the planets, all were subjected to primarily composed of tholeiitic ,*[35] although the so-called "Late Heavy Bombardment". About 60% parts are more silica-rich than typical basalt and may be of the surface of Mars shows a record of impacts from similar to andesitic rocks on Earth or silica glass. Re- that era,*[45]*[46]*[47] whereas much of the remaining gions of low show concentrations of surface is probably underlain by immense impact basins , with northern low albedo regions displaying caused by those events. There is evidence of an enormous higher than normal concentrations of sheet and impact basin in the northern hemisphere of Mars, span- high-silicon glass. Parts of the southern highlands in- ning 10,600 by 8,500 km (6,600 by 5,300 mi), or roughly clude detectable amounts of high-calcium . Lo- four times larger than the Moon's South Pole – calized concentrations of hematite and have also basin, the largest impact basin yet discovered.*[17]*[18] been found.*[36] Much of the surface is deeply covered This theory suggests that Mars was struck by a Pluto-sized by finely grained iron(III) oxide dust.*[37]*[38] body about four billion years ago. The event, thought to be the cause of the Martian hemispheric dichotomy, cre- Although Mars has no evidence of a current structured ated the smooth Borealis basin that covers 40% of the global magnetic field,*[42] observations show that parts planet.*[48]*[49] of the planet's crust have been magnetized, and that - nating polarity reversals of its dipole field have occurred The geological history of Mars can be split into many in the past. This paleomagnetism of magnetically sus- periods, but the following are the three primary peri- ceptible minerals has properties that are similar to the ods:*[50]*[51] alternating bands found on the ocean floors of Earth. One theory, published in 1999 and re-examined in October • period (named after Noachis ): 2005 (with the help of the ), is Formation of the oldest extant surfaces of Mars, 4.5 2.1. PHYSICAL CHARACTERISTICS 21

billion years ago to 3.5 billion years ago. Noachian has a basic pH of 7.7, and contains 0.6% of the age surfaces are scarred by many large impact .*[55]*[56]*[57]*[58] craters. The bulge, a volcanic upland, is Streaks are common across Mars and new ones appear thought to have formed during this period, with ex- frequently on steep slopes of craters, troughs, and val- tensive flooding by liquid water late in the period. leys. The streaks are dark at first and get lighter with • period (named after ): age. Sometimes, the streaks start in a tiny area which then 3.5 billion years ago to 2.9–3.3 billion years ago. spread out for hundreds of metres. They have also been The Hesperian period is marked by the formation seen to follow the edges of boulders and other obstacles of extensive plains. in their path. The commonly accepted theories include that they are dark underlying layers of soil revealed after * • period (named after Amazonis Plani- avalanches of bright dust or dust devils. [59] Several ex- tia): 2.9–3.3 billion years ago to present. Amazo- planations have been put forward, some of which involve * * nian regions have few impact craters, but water or even the growth of organisms. [60] [61] are otherwise quite varied. Olympus Mons formed during this period, along with lava flows elsewhere on Mars. 2.1.4 Hydrology

Some geological activity is still taking place on Mars. Main article: The is home to sheet-like lava flows up Liquid water cannot exist on the surface of Mars due to to about 200 Mya. Water flows in the called the Fossae occurred less than 20 Mya, indi- cating equally recent volcanic intrusions.*[52] On Febru- ary 19, 2008, images from the Mars Reconnaissance Or- biter showed evidence of an avalanche from a 700 m high cliff.*[53]

2.1.3 Soil

Main article: Martian soil The Phoenix lander returned data showing Martian soil

Photomicrograph taken by Opportunity showing a gray hematite concretion, indicative of the past presence of liquid water

low atmospheric pressure, which is about 100 times thin- ner than Earth's,*[62] except at the lowest elevations for short periods.*[63]*[64] The two polar ice caps appear to be made largely of water.*[65]*[66] The volume of water ice in the south , if melted, would be suffi- cient to cover the entire planetary surface to a depth of 11 meters (36 ft).*[67] A permafrost mantle stretches from the pole to latitudes of about 60°.*[65] Exposure of silica-rich dust uncovered by the Spirit rover Large quantities of water ice are thought to be trapped within the thick cryosphere of Mars. Radar data to be slightly alkaline and containing elements such as from Mars Express and the Mars Reconnaissance Or- magnesium, , potassium and chlorine. These biter show large quantities of water ice both at the poles nutrients are found in gardens on Earth, and they are (July 2005)*[22]*[68] and at middle latitudes (November necessary for growth of plants.*[54] Experiments per- 2008).*[23] The Phoenix lander directly sampled water formed by the lander showed that the Martian soil ice in shallow Martian soil on July 31, 2008.*[25] 22 CHAPTER 2. MARS

Landforms visible on Mars strongly suggest that liq- uid water has existed on the planet's surface. Huge linear swathes of scoured ground, known as outflow channels, cut across the surface in around 25 places. These are thought to record which occurred dur- ing the catastrophic release of water from subsurface aquifers, though some of these structures have also been hypothesized to result from the action of or lava.*[69]*[70] One of the larger examples, Ma'adim Vallis is 700 km (430 mi) long and much bigger than the Grand with a width of 20 km (12 mi) and a depth of 2 km (1.2 mi) in some places. It is thought to have been carved by flowing water early in Mars's history.*[71] The Composition of“Yellowknife Bay”rocks – rock veins are higher youngest of these channels are thought to have formed in calcium and sulfur than “Portage”soil – APXS results – as recently as only a few million years ago.*[72] Else- Curiosity rover (March 2013). where, particularly on the oldest areas of the Martian sur- face, finer-scale, dendritic networks of valleys are spread across significant proportions of the landscape. Features of these valleys and their distribution strongly imply that they were carved by runoff resulting from rain or snow fall in early Mars history. Subsurface water flow and groundwater sapping may play important subsidiary roles in some networks, but precipitation was probably the root Francis McCubbin, a planetary scientist at the University cause of the incision in almost all cases.*[73] of New Mexico in Albuquerque looking at hydroxals in crystalline minerals from Mars, states that the amount of Along crater and canyon walls, there are also thousands water in the upper mantle of Mars is equal to or greater of features that appear similar to terrestrial gullies. The than that of Earth at 50–300 parts per million of water, gullies tend to be in the highlands of the southern hemi- which is enough to cover the entire planet to a depth of sphere and to face the Equator; all are poleward of 30° lat- 200–1,000 m (660–3,280 ft).*[85] itude. A number of authors have suggested that their for- mation process involves liquid water, probably from melt- On March 18, 2013, NASA reported evidence from in- ing ice,*[74]*[75] although others have argued for for- struments on the Curiosity rover of hydration, mation mechanisms involving or the likely hydrated calcium , in several rock samples movement of dry dust.*[76]*[77] No partially degraded including the broken fragments of “”rock and gullies have formed by and no superimposed “Sutton Inlier”rock as well as in veins and nodules impact craters have been observed, indicating that these in other rocks like “Knorr”rock and “Wernicke” * * * are young features, possibly even active today.*[75] rock. [86] [87] [88] Analysis using the rover's DAN in- strument provided evidence of subsurface water, amount- Other geological features, such as deltas and alluvial fans ing to as much as 4% water content, down to a depth of preserved in craters, are further evidence for warmer, 60 cm (24 in), in the rover's traverse from the Bradbury wetter conditions at some interval or intervals in earlier Landing site to the Yellowknife Bay area in the Glenelg * Mars history. [78] Such conditions necessarily require terrain.*[86] the widespread presence of crater across a large pro- portion of the surface, for which there is also indepen- Some researchers think that much of the low northern dent mineralogical, sedimentological and geomorpholog- plains of the planet were covered with an ocean hundreds * ical evidence.*[79] of meters deep, though this remains controversial. [89] In March 2015, scientists stated that such ocean might Further evidence that liquid water once existed on the sur- have been the size of Earth's Arctic Ocean. This find- face of Mars comes from the detection of specific min- ing was derived from the ratio of water and deuterium erals such as hematite and , both of which some- in the modern Martian atmosphere compared to the ra- * times form in the presence of water. [80] Some of the tio found on Earth. Eight times as much deuterium was evidence believed to indicate ancient water basins and found at Mars than exists on Earth, suggesting that an- flows has been negated by higher resolution studies by the cient Mars had significantly higher levels of water. Re- * Mars Reconnaissance Orbiter. [81] In 2004, Opportunity sults from the Curiosity rover had previously found a high detected the mineral . This forms only in the pres- ratio of deuterium in Crater, though not significantly ence of acidic water, which demonstrates that water once high enough to suggest the presence of an ocean. Other * existed on Mars. [82] More recent evidence for liquid scientists caution that this new study has not been con- water comes from the finding of the mineral on firmed, and point out that Martian climate models have the surface by NASA's Mars rover Opportunity in De- not yet shown that the planet was warm enough in the * * cember 2011. [83] [84] Additionally, the study leader past to support bodies of liquid water.*[90] 2.1. PHYSICAL CHARACTERISTICS 23

Polar caps The seasonal frosting of some areas near the southern ice cap results in the formation of transparent 1-metre- Main article: thick slabs of above the ground. With the ar- rival of spring, warms the subsurface and pres- sure from subliming CO2 builds up under a slab, elevat- ing and ultimately rupturing it. This leads to -like eruptions of CO2 gas mixed with dark basaltic sand or dust. This process is rapid, observed happening in the space of a few days, or months, a rate of change rather unusual in geology – especially for Mars. The gas rushing underneath a slab to the site of a geyser carves a -like pattern of radial channels under the ice, the process being the inverted equivalent of an erosion net- North polar early summer ice cap (1999) work formed by water draining through a single plug- hole.*[101]*[102]*[103]*[104]

2.1.5 Geography and naming of surface features

Main article: Geography of Mars South polar midsummer ice cap (2000) See also: Category:Surface features of Mars Although better remembered for mapping the Moon, Mars has two permanent polar ice caps. During a pole's winter, it lies in continuous darkness, chilling the surface and causing the deposition of 25–30% of the atmosphere * into slabs of CO2 ice (dry ice). [91] When the poles are again exposed to sunlight, the frozen CO2 sublimes, cre- ating enormous winds that sweep off the poles as fast as 400 km/h (250 mph). These seasonal actions trans- port large amounts of dust and water vapor, giving rise to Earth-like frost and large cirrus clouds. Clouds of water-ice were photographed by the Opportunity rover in 2004.*[92] A MOLA-based topographic map showing highlands (red and orange) dominating the southern hemisphere of Mars, lowlands The polar caps at both poles consist primarily (70%) of (blue) the northern. Volcanic plateaus delimit the northern plains water ice. Frozen carbon dioxide accumulates as a com- in some regions, whereas the highlands are punctuated by several paratively thin layer about one metre thick on the north large impact basins. cap in the northern winter only, whereas the south cap has a permanent dry ice cover about eight metres thick.*[93] Johann Heinrich Mädler and Wilhelm were the first This permanent dry ice cover at the south pole is pep- “areographers”. They began by establishing that most of pered by flat floored, shallow, roughly circular pits, which Mars's surface features were permanent and by more pre- repeat imaging shows are expanding by meters per year; cisely determining the planet's rotation period. In 1840, this suggests that the permanent CO2 cover over the south Mädler combined ten years of observations and drew the pole water ice is degrading over time.*[94] The north- first map of Mars. Rather than giving names to the var- ern polar cap has a diameter of about 1,000 km (620 ious markings, Beer and Mädler simply designated them mi) during the northern Mars summer,*[95] and contains with letters; Meridian Bay () was thus about 1.6 million cubic kilometres (380,000 cu mi) of ice, feature "a".*[105] which, if spread evenly on the cap, would be 2 km (1.2 mi) thick.*[96] (This compares to a volume of 2.85 mil- Today, features on Mars are named from a variety of lion cubic kilometres (680,000 cu mi) for the Greenland sources. Albedo features are named for classical mythol- ice sheet.) The southern polar cap has a diameter of 350 ogy. Craters larger than 60 km are named for deceased km (220 mi) and a thickness of 3 km (1.9 mi).*[97] The scientists and writers and others who have contributed to total volume of ice in the south polar cap plus the adja- the study of Mars. Craters smaller than 60 km are named cent layered deposits has also been estimated at 1.6 mil- for towns and villages of the world with populations of lion cubic km.*[98] Both polar caps show spiral troughs, less than 100,000. Large valleys are named for the word “Mars”or“star”in various languages; small valleys are which recent analysis of SHARAD ice penetrating radar * has shown are a result of katabatic winds that spiral due named for rivers. [106] to the Effect.*[99]*[100] Large albedo features retain many of the older names, but 24 CHAPTER 2. MARS

are often updated to reflect new knowledge of the nature of the features. For example, Olympica (the snows Arcadia of Olympus) has become Olympus Mons (Mount Olym- MC-04 pus).*[107] The surface of Mars as seen from Earth is divided into two kinds of areas, with differing albedo. The paler plains covered with dust and sand rich in red- Mare Acidalium dish iron oxides were once thought of as Martian “con- MC-05 tinents”and given names like (land of Arabia) or (Amazonian plain). The Ismenius Lacus dark features were thought to be seas, hence their names MC-06 Mare Erythraeum, Mare Sirenum and Aurorae Sinus. The largest dark feature seen from Earth is Syrtis Ma- jor Planum.*[108] The permanent northern polar ice cap Casius is named , whereas the southern cap is MC-07 called . Mars's equator is defined by its rotation, but the location Cebrenia of its Prime Meridian was specified, as was Earth's (at MC-08 Greenwich), by choice of an arbitrary point; Mädler and Beer selected a line in 1830 for their first maps of Mars. Amazonis After the spacecraft provided extensive im- MC-09 agery of Mars in 1972, a small crater (later called -0), located in the Sinus Meridiani“( Middle Bay”or“Merid- Tharsis ian Bay”), was chosen for the definition of 0.0° longitude MC-10 to coincide with the original selection.*[109] Because Mars has no oceans and hence no “sea level”, Lunae Palus a zero-elevation surface also had to be selected as a ref- MC-11 erence level; this is also called the areoid*[110] of Mars, analogous to the terrestrial geoid. Zero altitude was de- fined by the height at which there is 610.5 Pa (6.105 Oxia Palus mbar) of atmospheric pressure.*[111] This pressure cor- MC-12 responds to the triple point of water, and it is about 0.6% of the sea level surface pressure on Earth (0.006 Arabia * atm). [112] In practice, today this surface is defined di- MC-13 rectly from satellite gravity measurements.

Syrtis Major MC-14 Map of quadrangles

The following imagemap of the planet Mars is divided Amenthes into the 30 quadrangles defined by the United States Ge- MC-15 ological Survey*[113]*[114] The quadrangles are num- bered with the prefix“MC”for“Mars Chart.”*[115] Elysium Click on the quadrangle and you will be taken to the cor- MC-16 responding article pages. North is at the top; 0°N 180°W / 0°N 180°W is at the far left on the equator. The map Memnonia images were taken by the Mars Global Surveyor. MC-17 0°N 180°W / 0°N 180°W 0°N 0°W / 0°N −0°E Phoenicis 90°N 0°W / 90°N −0°E MC-18 MC-01

Coprates Mare Boreum MC-19 MC-02

Margaritifer Diacria MC-20 MC-03 2.1. PHYSICAL CHARACTERISTICS 25

ern highlands, pitted and cratered by ancient impacts. Re- Sabaeus search in 2008 has presented evidence regarding a theory MC-21 proposed in 1980 postulating that, four billion years ago, the northern hemisphere of Mars was struck by an ob- ject one-tenth to two-thirds the size of Earth's Moon. If Iapygia validated, this would make the northern hemisphere of MC-22 Mars the site of an 10,600 by 8,500 km (6,600 by 5,300 mi) in size, or roughly the area of Eu- Tyrrhenum rope, , and Australia combined, surpassing the South MC-23 Pole–Aitken basin as the largest impact crater in the Solar System.*[17]*[18]

Aeolis MC-24

Phaethontis MC-25 Fresh asteroid impact on Mars 3°20′N 219°23′E / 3.34°N Thaumasia 219.38°E - before/March 27 & after/March 28, 2012 MC-26 (MRO).*[116]

Mars is scarred by a number of impact craters: a total of Argyre 43,000 craters with a diameter of 5 km (3.1 mi) or greater MC-27 have been found.*[117] The largest confirmed of these is the Hellas impact basin, a light clearly vis- Noachis ible from Earth.*[118] Due to the smaller mass of Mars, MC-28 the probability of an object colliding with the planet is about half that of Earth. Mars is located closer to the Hellas asteroid belt, so it has an increased chance of being struck MC-29 by materials from that source. Mars is also more likely to be struck by short-period comets, i.e., those that lie within the orbit of Jupiter.*[119] In spite of this, there are far Eridania fewer craters on Mars compared with the Moon, because MC-30 the provides protection against small meteors. Some craters have a morphology that suggests Mare Australe the ground became wet after the impacted.*[120]

Volcanoes Impact topography Main article:

The Olympus Mons () is an extinct volcano in the vast upland region Tharsis, which contains several other large volcanoes. Olympus Mons is roughly three times the height of , which in comparison stands at just over 8.8 km (5.5 mi).*[121] It is either the tallest or second tallest mountain in the Solar System, depending on how it is measured, with various sources giving figures ranging from about 21 to 27 km (13 to 17 mi) high.*[122]*[123]

Tectonic sites crater and Spirit rover's lander The large canyon, Valles Marineris (Latin for Mariner The dichotomy of Martian topography is striking: north- Valleys, also known as Agathadaemon in the old canal ern plains flattened by lava flows contrast with the south- maps), has a length of 4,000 km (2,500 mi) and a depth 26 CHAPTER 2. MARS

the“seven sisters”.*[127] Cave entrances measure from 100 to 252 m (328 to 827 ft) wide and they are believed to be at least 73 to 96 m (240 to 315 ft) deep. Because light does not reach the floor of most of the caves, it is possible that they extend much deeper than these lower estimates and widen below the surface. “Dena”is the only exception; its floor is visible and was measured to be 130 m (430 ft) deep. The interiors of these caverns may be protected from , UV radiation, solar flares and high energy particles that bombard the planet's surface.*[128]

2.1.6 Atmosphere

Main article: Atmosphere of Mars

Viking orbiter view of Olympus Mons

Escaping atmosphere on Mars (carbon, oxygen, and MOLA colorized shaded-relief map of western hemisphere of hydrogen) by MAVEN in UV.*[129] Mars showing Tharsis bulge (shades of red and brown). Tall volcanoes appear white. Mars lost its magnetosphere 4 billion years ago,*[130] possibly because of numerous asteroid strikes,*[131] of up to 7 km (4.3 mi). The length of Valles Marineris so the solar wind interacts directly with the Martian is equivalent to the length of and extends across , lowering the atmospheric density by strip- one-fifth the circumference of Mars. By comparison, the ping away atoms from the outer layer. Both Mars on Earth is only 446 km (277 mi) long Global Surveyor and Mars Express have detected ionised and nearly 2 km (1.2 mi) deep. Valles Marineris was atmospheric particles trailing off into space behind formed due to the swelling of the Tharsis area which Mars,*[130]*[132] and this atmospheric loss is being caused the crust in the area of Valles Marineris to col- studied by the MAVEN orbiter. Compared to Earth, the lapse. In 2012, it was proposed that Valles Marineris is atmosphere of Mars is quite rarefied. Atmospheric pres- not just a , but also a plate boundary where 150 sure on the surface today ranges from a low of 30 Pa km (93 mi) of transverse motion has occurred, making (0.030 kPa) on Olympus Mons to over 1,155 Pa (1.155 Mars a planet with possibly a two-plate tectonic arrange- kPa) in , with a mean pressure at the sur- ment.*[124]*[125] face level of 600 Pa (0.60 kPa).*[133] The highest atmo- spheric density on Mars is equal to that found 35 km (22 mi)*[134] above Earth's surface. The resulting mean sur- Holes face pressure is only 0.6% of that of Earth (101.3 kPa). The scale height of the atmosphere is about 10.8 km (6.7 Images from the Thermal Emission Imaging System mi),*[135] which is higher than Earth's (6 km (3.7 mi)) (THEMIS) aboard NASA's Mars Odyssey orbiter have because the surface is only about 38% revealed seven possible cave entrances on the flanks of of Earth's, an effect offset by both the lower temperature the volcano .*[126] The caves, named after and 50% higher average molecular weight of the atmo- loved ones of their discoverers, are collectively known as sphere of Mars. 2.1. PHYSICAL CHARACTERISTICS 27

Potential sources and sinks of methane (CH4) on Mars.

reach.*[145] The first measurements with the Tunable Laser Spectrometer (TLS) indicated that there is less than 5 ppb of methane at the landing site at the point of the measurement.*[146]*[147]*[148]*[149] On Septem- The tenuous atmosphere of Mars visible on the horizon. ber 19, 2013, NASA scientists, from further measure- ments by Curiosity, reported no detection of atmospheric methane with a measured value of 0.18±0.67 ppbv corre- The atmosphere of Mars consists of about 96% carbon sponding to an upper limit of only 1.3 ppbv (95% confi- dioxide, 1.93% and 1.89% along with dence limit) and, as a result, conclude that the probability traces of oxygen and water.*[6]*[136] The atmosphere of current methanogenic microbial activity on Mars is re- is quite dusty, containing particulates about 1.5 µm in di- duced.*[150]*[151]*[152] ameter which give the Martian sky a tawny color when seen from the surface.*[137] Methane has been detected in the Martian atmosphere with a mole fraction of about 30 ppb;*[14]*[138] it oc- curs in extended plumes, and the profiles imply that the methane was released from discrete regions. In northern midsummer, the principal plume contained 19,000 met- ric tons of methane, with an estimated source strength of 0.6 per second.*[139]*[140] The profiles suggest that there may be two local source regions, the first centered near 30°N 260°W / 30°N 260°W and the second near 0°N 310°W / 0°N 310°W.*[139] It is es- timated that Mars must produce 270 tonnes per year of methane.*[139]*[141] The implied methane destruction lifetime may be as long as about 4 Earth years and as short as about 0.6 Earth years.*[139]*[142] This rapid turnover would indicate an active source of the gas on the planet. Volcanic activity, cometary impacts, and the presence of methanogenic microbial life forms are among possi- ble sources. Methane could also be produced by a non- biological process called serpentinization*[lower-alpha 2] involving water, carbon dioxide, and the mineral olivine, * which is known to be common on Mars. [143] The Martian atmosphere as imaged by the Mars Orbiter Mission The Curiosity rover, which landed on Mars in August Spacecraft 2012, is able to make measurements that distinguish between different isotopologues of methane,*[144] but The Mars Orbiter Mission by India is currently searching even if the mission is to determine that microscopic Mar- for methane in the armosphere,*[153] while the ExoMars tian life is the source of the methane, the life forms Trace Gas Orbiter, planned to launch in 2016, would fur- likely reside far below the surface, outside of the rover's ther study the methane as well as its decomposition prod- 28 CHAPTER 2. MARS

ucts, such as formaldehyde and methanol.*[154] north, and near aphelion when it is winter in the south- On 16 December 2014, NASA reported the Curiosity ern hemisphere and summer in the north. As a result, the rover detected a“tenfold spike”, likely localized, in the seasons in the southern hemisphere are more extreme and amount of methane in the Martian atmosphere. Sample the seasons in the northern are milder than would other- measurements taken “a dozen times over 20 months” wise be the case. The summer in the south can reach up to 30 K (30 °C; 54 °F) warmer than the showed increases in late 2013 and early 2014, averaging * “7 parts of methane per billion in the atmosphere.”Be- equivalent summer temperatures in the north. [161] fore and after that, readings averaged around one-tenth Mars also has the largest dust storms in the Solar System. that level.*[155]*[156] These can vary from a storm over a small area, to gigantic Ammonia was also tentatively detected on Mars by the storms that cover the entire planet. They tend to occur when Mars is closest to the Sun, and have been shown to Mars Express satellite, but with its relatively short life- * time, it is not clear what produced it.*[157] Ammonia is increase the global temperature. [162] not stable in the Martian atmosphere and breaks down after a few hours. One possible source is volcanic activ- ity.*[157] 2.2 Orbit and rotation On 18 March 2015, NASA reported the detection of an aurora that is not fully understood and an unexplained Main article: dust cloud in the atmosphere of Mars.*[158] Mars's average distance from the Sun is roughly 230 mil-

2.1.7 Climate

Main article: Dust storm on Mars.

November 18, 2012

November 25, 2012 Opportunity and Curiosity rovers are noted. Mars is about 230 million kilometres (143,000,000 mi) from the Of all the planets in the Solar System, the seasons of Mars Sun; its orbital period is 687 (Earth) days, depicted in red. Earth's are the most Earth-like, due to the similar tilts of the orbit is in blue. two planets' rotational axes. The lengths of the Martian seasons are about twice those of Earth's because Mars's lion kilometres (143,000,000 mi), and its orbital period is 687 (Earth) days. The solar day (or ) on Mars is only greater distance from the Sun leads to the Martian year being about two Earth years long. Martian surface tem- slightly longer than an Earth day: 24 hours, 39 minutes, and 35.244 seconds. A Martian year is equal to 1.8809 peratures vary from lows of about −143 °C (−225 °F) * at the winter polar caps*[8] to highs of up to 35 °C (95 Earth years, or 1 year, 320 days, and 18.2 hours. [6] °F) in equatorial summer.*[9] The wide range in temper- The axial tilt of Mars is 25.19 degrees relative to its atures is due to the thin atmosphere which cannot store orbital plane, which is similar to the axial tilt of Earth.*[6] much solar heat, the low atmospheric pressure, and the As a result, Mars has seasons like Earth, though on Mars, low thermal inertia of Martian soil.*[159] The planet is they are nearly twice as long because its orbital period is also 1.52 times as far from the Sun as Earth, resulting in that much longer. Currently, the orientation of the north just 43% of the amount of sunlight.*[160] pole of Mars is close to the star .*[11] Mars passed an aphelion in March 2010*[163] and its perihelion in If Mars had an Earth-like orbit, its seasons would be sim- * ilar to Earth's because its axial tilt is similar to Earth's. March 2011. [164] The next aphelion came in Febru- ary 2012*[164] and the next perihelion came in January The comparatively large eccentricity of the Martian orbit * has a significant effect. Mars is near perihelion when it 2013. [164] is summer in the southern hemisphere and winter in the Mars has a relatively pronounced of 2.3. SEARCH FOR LIFE 29

about 0.09; of the seven other planets in the Solar System, only Mercury has a larger orbital eccentricity. It is known that in the past, Mars has had a much more circular orbit than it does currently. At one point, 1.35 million Earth years ago, Mars had an eccentricity of roughly 0.002, much less than that of Earth today.*[165] Mars's cycle of eccentricity is 96,000 Earth years compared to Earth's cy- cle of 100,000 years.*[166] Mars also has a much longer cycle of eccentricity with a period of 2.2 million Earth years, and this overshadows the 96,000-year cycle in the eccentricity graphs. For the last 35,000 years, the orbit of Mars has been getting slightly more eccentric because of the gravitational effects of the other planets. The closest distance between Earth and Mars will continue to mildly decrease for the next 25,000 years.*[167]

2.3 Search for life

Main articles: and Viking lander biological experiments The current understanding of —the

Curiosity rover self-portrait at "" (October 31, 2012), with the rim of Gale Crater and the slopes of Aeolis Mons in the distance.

Evidence suggests that the planet was once significantly more habitable than it is today, but whether living organisms ever existed there remains unknown. The Lander - sampling arm created deep trenches, scooping Viking probes of the mid-1970s carried experiments de- up material for tests (). signed to detect in Martian soil at their respective landing sites and had positive results, includ- ability of a world to develop and sustain life—favors plan- ing a temporary increase of CO2 production on exposure ets that have liquid water on their surface. This most often to water and nutrients. This sign of life was later dis- requires that the orbit of a planet lie within the habitable puted by some scientists, resulting in a continuing debate, zone, which for the Sun extends from just beyond Venus * with NASA scientist Levin asserting that Viking to about the semi-major axis of Mars. [168] During per- may have found life. A re-analysis of the Viking data, ihelion, Mars dips inside this region, but the planet's thin in light of modern knowledge of extremophile forms of (low-pressure) atmosphere prevents liquid water from ex- life, has suggested that the Viking tests were not sophis- isting over large regions for extended periods. The past ticated enough to detect these forms of life. The tests flow of liquid water demonstrates the planet's potential could even have killed a (hypothetical) life form.*[171] for habitability. Some recent evidence has suggested that Tests conducted by the Phoenix Mars lander have shown any water on the Martian surface may have been too salty * that the soil has a alkaline pH and it contains magnesium, and acidic to support regular terrestrial life. [169] sodium, potassium and chloride.*[172] The soil nutrients The lack of a magnetosphere and extremely thin atmo- may be able to support life, but life would still have to sphere of Mars are a challenge: the planet has little heat be shielded from the intense ultraviolet light.*[173] A re- transfer across its surface, poor insulation against bom- cent analysis of EETA79001 found 0.6 * * * bardment of the solar wind and insufficient atmospheric ppm ClO4 −, 1.4 ppm ClO3 −, and 16 ppm NO3 −, most * pressure to retain water in a liquid form (water instead likely of martian origin. The ClO3 − suggests presence * sublimes to a gaseous state). Mars is also nearly, or of other highly oxidizing oxychlorines such as ClO2 − perhaps totally, geologically dead; the end of volcanic or ClO, produced both by UV oxidation of Cl and X- * activity has apparently stopped the recycling of chemi- ray radiolysis of ClO4 −. Thus only highly refractory cals and minerals between the surface and interior of the and/or well-protected (sub-surface) organics or life forms planet.*[170] are likely to survive.*[174] In addition, recent analysis 30 CHAPTER 2. MARS

of the Phoenix WCL showed that the Ca(ClO4)2 in the Phoenix soil has not interacted with liquid water of any form, perhaps for as long as 600 Myr. If it had, the highly soluble Ca(ClO4)2 in contact with liquid water would have formed only CaSO4. This suggests a severely arid environment, with minimal or no liquid water inter- action.*[175] At the lab, some fascinating shapes have been found in the meteorite ALH84001, which is thought to have originated from Mars. Some scientists propose that these geometric shapes could be fossilized Panorama of crater, where Spirit rover examined volcanic microbes extant on Mars before the meteorite was blasted into space by a meteor strike and sent on a 15 million-year to Earth. An exclusively inorganic origin for the 6, 2012 UTC. It is larger and more advanced than the * shapes has also been proposed. [176] Mars Exploration Rovers, with a movement rate up to Small quantities of methane and formaldehyde re- 90 m (300 ft) per .*[183] Experiments include a cently detected by Mars orbiters are both claimed to laser chemical sampler that can deduce the make-up of be possible evidence for life, as these chemical com- rocks at a distance of 7 m (23 ft).*[184] On February 10 pounds would quickly break down in the Martian atmo- the Curiosity rover obtained the first deep rock samples sphere.*[177]*[178] Alternatively, these compounds may ever taken from another planetary body, using its onboard instead be replenished by volcanic or other geological drill.*[185] * means, such as serpentinization. [143] On September 24, 2014, Mars Orbiter Mission (MOM), launched by the Indian Space Research Organisation, reached Mars orbit. ISRO launched MOM on Novem- 2.4 Habitability ber 5, 2013, with the aim of analyzing the Martian atmo- sphere and topography. The Mars Orbiter Mission used The German Aerospace Center discovered that Earth a Hohmann transfer orbit to escape Earth's gravitational lichens can survive in simulated Mars conditions, mak- influence and catapult into a nine-month-long voyage to ing the presence of life more plausible according to Mars. The mission is the first successful Asian interplan- researcher Tilman Spohn.*[179] The simulation based etary mission.*[186] temperatures, atmospheric pressure, minerals, and light Several plans for a have been pro- * on data from Mars probes. [179] An instrument called posed throughout the 20th century and into the 21st cen- REMS is designed to provide new clues about the sig- tury but no active plan has an arrival date sooner than nature of the Martian general circulation, microscale 2025. weather systems, local hydrological cycle, destructive po- tential of UV radiation, and subsurface habitability based on ground-atmosphere interaction.*[180]*[181] It landed on Mars as part of Curiosity (MSL) in August 2012. 2.6

Main article: Astronomy on Mars 2.5 Exploration missions With the existence of various orbiters, landers, and rovers, it is now possible to do astronomy from Mars. Main article: Although Mars's moon Phobos appears about one third In addition to observation from Earth, some of the lat- the of the as it appears from est Mars information comes from seven active probes on Earth, Deimos appears more or less star-like and appears or in orbit around Mars, including five orbiters and two only slightly brighter than Venus does from Earth.*[187] * rovers. This includes 2001 Mars Odyssey, [182] Mars Ex- There are various phenomena, well-known on Earth, press, Mars Reconnaissance Orbiter, MAVEN, Mars Or- that have been observed on Mars, such as meteors and biter Mission, Opportunity, and Curiosity. .*[188] A of Earth as seen from Mars Dozens of unmanned spacecraft, including orbiters, will occur on November 10, 2084.*[189] There are also landers, and rovers, have been sent to Mars by the Soviet transits of Mercury and transits of Venus, and the moons Union, the United States, Europe, and India to study the Phobos and Deimos are of sufficiently small angular planet's surface, climate, and geology. The public can re- diameter that their partial “”of the Sun are quest images of Mars via the HiWish program. best considered transits (see Transit of Deimos from * * The Mars Science Laboratory, named Curiosity, launched Mars). [190] [191] on November 26, 2011, and reached Mars on August On October 19, 2014, Comet Siding Spring passed ex- 2.7. VIEWING 31

POV: Mars

Phobos transits the Sun (Opportunity; March 10, 2004).

Comet Siding Spring to pass near Mars on October 19, 2014 (Hubble; March 11, 2014).

Close encounter of Comet Siding Spring with the planet tremely close to Mars, so close that the may have Mars enveloped Mars.*[192]*[193]*[194]*[195]*[196]*[197] (composite image; Hubble ST; October 19, 2014). Comet Siding Spring Mars flyby on October 19, 2014 (artist's concepts)

2.7 Viewing

Because the orbit of Mars is eccentric, its apparent mag- nitude at opposition from the Sun can range from −3.0 to −1.4. The minimum brightness is magnitude +1.6 when POV: Universe the planet is in conjunction with the Sun.*[10] Mars usu- ally appears distinctly yellow, orange, or red; the actual color of Mars is closer to butterscotch, and the redness seen is just dust in the planet's atmosphere. NASA's Spirit rover has taken pictures of a greenish-brown, mud- colored landscape with blue-grey rocks and patches of light red sand.*[198] When farthest away from Earth, it is more than seven times as far from the latter as when it is POV: Comet closest. When least favorably positioned, it can be lost in 32 CHAPTER 2. MARS

days.

Absolute, around the present time

Animation of the apparent retrograde motion of Mars in 2003 as seen from Earth the Sun's glare for months at a time. At its most favorable times—at 15- or 17-year intervals, and always between late July and late September—a lot of surface detail can be seen with a telescope. Especially noticeable, even at low magnification, are the polar ice caps.*[199] Mars oppositions from 2003–2018, viewed from above the eclip- As Mars approaches opposition, it begins a period of tic with Earth centered retrograde motion, which means it will appear to move backwards in a looping motion with respect to the back- ground stars. The duration of this retrograde motion lasts Mars made its closest approach to Earth and maximum for about 72 days, and Mars reaches its peak luminosity apparent brightness in nearly 60,000 years, 55,758,006 in the middle of this motion.*[200] km (0.37271925 AU; 34,646,419 mi), magnitude −2.88, on August 27, 2003 at 9:51:13 UT. This occurred when Mars was one day from opposition and about three days 2.7.1 Closest approaches from its perihelion, making it particularly easy to see from Earth. The last time it came so close is estimated to have Relative been on September 12, 57 617 BC, the next time be- ing in 2287.*[205] This record approach was only slightly The point at which Mars's geocentric longitude is 180° closer than other recent close approaches. For instance, different from the Sun's is known as opposition, which is the minimum distance on August 22, 1924 was 0.37285 near the time of closest approach to Earth. The time of AU, and the minimum distance on August 24, 2208 will opposition can occur as much as 8.5 days away from the be 0.37279 AU.*[166] closest approach. The distance at close approach varies between about 54*[201] and about 103 million km due to the planets' elliptical orbits, which causes comparable variation in angular size.*[202] The last Mars opposition 2.8 Historical observations occurred on April 8, 2014 at a distance of about 93 mil- lion km.*[203] The next Mars opposition occurs on May 22, 2016 at a distance of 76 million km.*[203] The aver- Main article: History of Mars observation age time between the successive oppositions of Mars, its synodic period, is 780 days but the number of days be- The history of observations of Mars is marked by the op- tween the dates of successive oppositions can range from * positions of Mars, when the planet is closest to Earth and 764 to 812. [204] hence is most easily visible, which occur every couple of As Mars approaches opposition it begins a period of years. Even more notable are the perihelic oppositions retrograde motion, which makes it appear to move back- of Mars, which occur every 15 or 17 years and are dis- wards in a looping motion relative to the background tinguished because Mars is close to perihelion, making it stars. The duration of this retrograde motion is about 72 even closer to Earth. 2.8. HISTORICAL OBSERVATIONS 33

2.8.1 Ancient and medieval observations

The existence of Mars as a wandering object in the night sky was recorded by the ancient Egyptian astronomers and by 1534 BCE they were familiar with the retrograde motion of the planet.*[206] By the period of the Neo- Babylonian Empire, the Babylonian astronomers were Mars sketched as observed by sometime before making regular records of the positions of the planets and 1914. (South top) systematic observations of their behavior. For Mars, they knew that the planet made 37 synodic periods, or 42 cir- cuits of the zodiac, every 79 years. They also invented arithmetic methods for making minor corrections to the predicted positions of the planets.*[207]*[208] In the fourth century BCE, Aristotle noted that Mars disappeared behind the Moon during an , in- Map of Mars from Hubble Space Telescope as seen near * dicating the planet was farther away. [209] , a the 1999 opposition. (North top) * Greek living in Alexandria, [210] attempted to address Main article: the problem of the orbital motion of Mars. Ptolemy's model and his collective work on astronomy was pre- sented in the multi-volume collection Almagest, which By the , the resolution of telescopes reached became the authoritative treatise on Western astronomy a level sufficient for surface features to be identified. A for the next fourteen centuries.*[211] Literature from an- perihelic opposition of Mars occurred on September 5, cient China confirms that Mars was known by Chinese as- 1877. In that year, Italian astronomer Giovanni Schia- tronomers by no later than the fourth century BCE.*[212] parelli used a 22 cm (8.7 in) telescope in Milan to help In the fifth century CE, the Indian astronomical text Surya produce the first detailed map of Mars. These maps no- Siddhanta estimated the diameter of Mars.*[213] In the tably contained features he called canali, which were later East Asian cultures, Mars is traditionally referred to as the shown to be an optical illusion. These canali were suppos- “fire star”(火星), based on the Five elements.*[214] edly long, straight lines on the surface of Mars, to which he gave names of famous rivers on Earth. His term, which During the seventeenth century, measured means “channels”or “grooves”, was popularly mis- the diurnal of Mars that Johannes used translated in English as “canals”.*[220]*[221] to make a preliminary calculation of the relative distance to the planet.*[215] When the telescope became avail- Influenced by the observations, the orientalist Percival able, the diurnal parallax of Mars was again measured in Lowell founded an observatory which had 30 and 45 cm an effort to determine the Sun-Earth distance. This was (12 and 18 in) telescopes. The observatory was used first performed by Giovanni Domenico Cassini in 1672. for the exploration of Mars during the last good oppor- The early parallax measurements were hampered by the tunity in 1894 and the following less favorable opposi- quality of the instruments.*[216] The only occultation of tions. He published several books on Mars and life on the * Mars by Venus observed was that of October 13, 1590, planet, which had a great influence on the public. [222] seen by Michael Maestlin at Heidelberg.*[217] In 1610, The canali were also found by other astronomers, like Mars was viewed by Galileo Galilei, who was first to see Henri Joseph Perrotin and Louis Thollon in Nice, using * * it via telescope.*[218] The first person to draw a map of one of the largest telescopes of that time. [223] [224] Mars that displayed any terrain features was the Dutch The seasonal changes (consisting of the diminishing of astronomer .*[219] the polar caps and the dark areas formed during Martian summer) in combination with the canals lead to specula- tion about life on Mars, and it was a long-held belief that Mars contained vast seas and vegetation. The telescope never reached the resolution required to give proof to 2.8.2 Martian “canals” any speculations. As bigger telescopes were used, fewer long, straight canali were observed. During an obser- vation in 1909 by Flammarion with an 84 cm (33 in) telescope, irregular patterns were observed, but no canali were seen.*[225] Even in the 1960s articles were published on Martian bi- ology, putting aside explanations other than life for the seasonal changes on Mars. Detailed scenarios for the metabolism and chemical cycles for a functional ecosys- Map of Mars by 34 CHAPTER 2. MARS

tem have been published.*[226]

2.8.3 Spacecraft visitation

Main article: Exploration of Mars Once spacecraft visited the planet during NASA's

Foothills of Aeolis Mons (“”) (white-balanced im- age).

Mariner missions in the 1960s and 70s these concepts 's books on the subject put forward the were radically broken. In addition, the results of the standard notion of a planet that was a drying, cooling, Viking life-detection experiments aided an intermission dying world with ancient civilizations constructing irriga- in which the hypothesis of a hostile, dead planet was gen- tion works.*[230] * erally accepted. [227] Many other observations and proclamations by notable Mariner 9 and Viking allowed better maps of Mars to be personalities added to what has been termed “Mars made using the data from these missions, and another ma- Fever”.*[231] In 1899 while investigating atmospheric jor leap forward was the Mars Global Surveyor mission, radio noise using his receivers in his Colorado Springs launched in 1996 and operated until late 2006, that al- lab, inventor Nikola Tesla observed repetitive signals that lowed complete, extremely detailed maps of the Martian he later surmised might have been radio communications topography, magnetic field and surface minerals to be ob- coming from another planet, possibly Mars. In a 1901 tained.*[228] These maps are now available online; for interview Tesla said: example, at Google Mars. Mars Reconnaissance Orbiter and Mars Express continued exploring with new instru- It was some time afterward when the ments, and supporting lander missions. thought flashed upon my mind that the distur- bances I had observed might be due to an in- telligent control. Although I could not deci- 2.9 In culture pher their meaning, it was impossible for me to think of them as having been entirely acci- dental. The feeling is constantly growing on me Main articles: Mars in culture and Mars in fiction that I had been the first to hear the greeting of Mars is named after the Roman god of war. In differ- one planet to another.*[232] ent cultures, Mars represents masculinity and youth. Its symbol, a circle with an arrow pointing out to the upper Tesla's theories gained support from Lord Kelvin who, right, is also used as a symbol for the male gender. while visiting the United States in 1902, was reported The many failures in Mars exploration probes resulted in a to have said that he thought Tesla had picked up Mar- satirical counter-culture blaming the failures on an Earth- tian signals being sent to the United States.*[233] Kelvin Mars "Bermuda Triangle", a "Mars Curse", or a "Great “emphatically”denied this report shortly before depart- Galactic Ghoul" that feeds on Martian spacecraft.*[229] ing America:“What I really said was that the inhabitants of Mars, if there are any, were doubtless able to see New York, particularly the glare of the electricity.”*[234] 2.9.1 Intelligent “Martians” In a New York Times article in 1901, Edward Charles Pickering, director of the Harvard College Observatory, Main article: Mars in fiction said that they had received a telegram from Lowell Obser- vatory in Arizona that seemed to confirm that Mars was The fashionable idea that Mars was populated by trying to communicate with Earth.*[235] intelligent Martians exploded in the late 19th cen- tury. Schiaparelli's“canali”observations combined with Early in December 1900, we received from 2.9. IN CULTURE 35

An 1893 soap ad playing on the popular idea that Mars was populated Martian tripod illustration from the 1906 French edition of by H.G. in Arizona a telegram that a shaft of light had been seen to project from The depiction of Mars in fiction has been stimulated by Mars (the Lowell observatory makes a spe- its dramatic red color and by nineteenth century scientific cialty of Mars) lasting seventy minutes. I wired speculations that its surface conditions might support not these facts to Europe and sent out neostyle just life but intelligent life.*[237] Thus originated a large copies through this country. The observer number of science fiction scenarios, among which is H. G. there is a careful, reliable man and there is no Wells' The War of the Worlds, published in 1898, in which reason to doubt that the light existed. It was Martians seek to escape their dying planet by invading given as from a well-known geographical point Earth. A subsequent US radio adaptation of The War of on Mars. That was all. Now the story has gone the Worlds on October 30, 1938, by was the world over. In Europe it is stated that I presented as a live news broadcast and became notorious have been in communication with Mars, and all for causing a public panic when many listeners mistook it sorts of exaggerations have spring up. What- for the truth.*[238] ever the light was, we have no means of know- ing. Whether it had intelligence or not, no one Influential works included 's The Mar- can say. It is absolutely inexplicable.*[235] tian Chronicles, in which human explorers accidentally destroy a Martian civilization, Edgar Rice ' Barsoom series, C. S. Lewis' novel Pickering later proposed creating a set of mirrors in (1938),*[239] and a number of Robert A. stories Texas, intended to signal Martians.*[236] before the mid-sixties.*[240] In recent decades, the high-resolution mapping of the sur- Author Jonathan made reference to the moons of face of Mars, culminating in Mars Global Surveyor, re- Mars, about 150 years before their actual discovery by vealed no artifacts of habitation by “intelligent”life, , detailing reasonably accurate descriptions of but pseudoscientific speculation about intelligent life on their orbits, in the 19th chapter of his novel Gulliver's Mars continues from commentators such as Richard C. Travels.*[241] Hoagland. Reminiscent of the canali controversy, some speculations are based on small scale features perceived A comic figure of an intelligent Martian, Marvin the Mar- in the spacecraft images, such as 'pyramids' and the 'Face tian, appeared on television in 1948 as a character in on Mars'. Planetary astronomer wrote: the Looney Tunes animated cartoons of Warner Broth- ers, and has continued as part of popular culture to the * Mars has become a kind of mythic arena present. [242] onto which we have projected our Earthly After the Mariner and Viking spacecraft had returned hopes and fears.*[221] pictures of Mars as it really is, an apparently lifeless 36 CHAPTER 2. MARS

and canal-less world, these ideas about Mars had to be ters Phobos (panic/fear) and Deimos (terror/dread), who, abandoned, and a vogue for accurate, realist depictions in , accompanied their father Ares, god of human colonies on Mars developed, the best known of war, into battle. Mars was the Roman counterpart of of which may be Kim Stanley Robinson's Mars trilogy. Ares.*[245]*[246] In modern Greek, though, the planet Pseudo-scientific speculations about the Face on Mars retains its ancient name Ares (Aris: Άρης).*[247] and other enigmatic landmarks spotted by space probes From the surface of Mars, the motions of Phobos and have meant that ancient civilizations continue to be a pop- * Deimos appear different from that of the Moon. Phobos ular theme in science fiction, especially in film. [243] rises in the west, sets in the east, and rises again in just 11 The theme of a Martian colony that fights for indepen- hours. Deimos, being only just outside dence from Earth is a major plot element in the novels – where the orbital period would match the planet's pe- of Greg Bear as well as the movie Total Recall (based riod of rotation – rises as expected in the east but slowly. on a short story by Philip K. Dick) and the television se- Despite the 30 hour orbit of Deimos, 2.7 days elapse be- ries Babylon 5. Some video games also use this element, tween its rise and set for an equatorial observer, as it including Red Faction and the Zone of the Enders series. slowly falls behind the rotation of Mars.*[248] Mars (and its moons) were also the setting for the popular Doom video game franchise and the later Martian Gothic.

2.10 Moons

Main articles: , Phobos (moon) and Deimos (moon)

Orbits of Phobos and Deimos (to scale)

Because the orbit of Phobos is below synchronous alti- tude, the tidal forces from the planet Mars are gradually lowering its orbit. In about 50 million years, it could ei- Enhanced-color HiRISE image of Phobos, showing a ther crash into Mars's surface or break up into a ring struc- series of mostly parallel grooves and crater chains, with ture around the planet.*[248] its crater at right The origin of the two moons is not well understood. Their low albedo and carbonaceous composition have been regarded as similar to asteroids, supporting the cap- ture theory. The unstable orbit of Phobos would seem to point towards a relatively recent capture. But both have circular orbits, near the equator, which is unusual for cap- tured objects and the required capture dynamics are com- plex. Accretion early in the history of Mars is also plausi- ble, but would not account for a composition resembling asteroids rather than Mars itself, if that is confirmed. A third possibility is the involvement of a third body or some kind of impact disruption.*[249] More recent Enhanced-color HiRISE image of Deimos (not to scale), lines of evidence for Phobos having a highly porous in- showing its smooth blanket of . terior,*[250] and suggesting a composition containing mainly phyllosilicates and other minerals known from Mars has two relatively small natural moons, Phobos Mars,*[251] point toward an origin of Phobos from mate- (about 22 km (14 mi) in diameter) and Deimos (about 12 rial ejected by an impact on Mars that reaccreted in Mar- km (7.5 mi) in diameter), which orbit close to the planet. tian orbit,*[252] similar to the prevailing theory for the is a long-favored theory, but their origin origin of Earth's moon. Although the VNIR spectra of remains uncertain.*[244] Both satellites were discovered the moons of Mars resemble those of outer-belt - in 1877 by Asaph Hall; they are named after the charac- oids, the thermal infrared spectra of Phobos are reported 2.13. NOTES 37 to be inconsistent with of any class.*[251] 2.13 Notes Mars may have additional moons smaller than 50 to 100 metres (160 to 330 ft) in diameter, and a dust ring is pre- [1] Best fit ellipsoid * dicted between Phobos and Deimos. [253] [2] There are many serpentinization reactions. Olivine is a solid solution between and fayalite whose gen- eral formula is (Fe,Mg)2SiO4. The reaction producing 2.11 Gallery methane from olivine can be written as: Forsterite + Fay- alite + Water + Carbonic → Serpentine + + Methane , or (in balanced form): 18Mg2SiO4 + 6Fe2SiO4 • Streaks - on slopes in . + 26H2O + CO2 → 12Mg3Si2O5(OH)4 + 4Fe3O4 + CH4 • Avalanche - down 700 m slope (north pole). • Nanedi Valles inner channel. 2.14 References • Valles Marineris (2001 Mars Odyssey). [1] Yeomans, Donald K. (July 13, 2006). “HORIZONS • Mars - cave entrances (possible). Web-Interface for Mars (Major Body=499)". JPL Hori- zons On-Line Ephemeris System. Retrieved August 8, • Mars - suspected lava-tube skylight. 2007.—Select “Ephemeris Type: Orbital Elements”, “Time Span: 2000-01-01 12:00 to 2000-01-02”.(“Tar- • Mars - North Pole area. get Body: Mars”and“Center: Sun”should be defaulted to.) Results are instantaneous osculating values at the pre- cise J2000 epoch. 2.12 See also [2] “The MeanPlane (Invariable plane) of the Solar System passing through the barycenter”. April 3, 2009. Retrieved April 10, 2009. (produced with Solex 10 written by Aldo • — C/2013 A1 a comet passing near Mars in 2014 Vitagliano; see also invariable plane)

• [3] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, Michael F. et al. (2007). “Report of the IAU/IAG • Working Group on cartographic coordinates and rotational elements: 2006”. Celestial Mechan- • — Darian calendar time-keeping system ics and Dynamical Astronomy 98 (3): 155–180. Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- • Geodynamics on Mars 007-9072-y. • Geology of Mars [4] Lodders, Katharina; Fegley, (1998). The planetary scientist's companion. Oxford University Press US. p. 190. • Extraterrestrial life ISBN 0-19-511694-1. • Exploration of Mars [5] Folkner, W. M. et al. (1997). “Interior Struc- • ture and Seasonal Mass Redistribution of Mars from List of artificial objects on Mars Radio Tracking of Mars Pathfinder”. Science 278 (5344): 1749–1752. Bibcode:1997Sci...278.1749F. • List of chasmata on Mars doi:10.1126/science.278.5344.1749. ISSN 0036-8075. • List of craters on Mars [6] Williams, David R. (September 1, 2004). “Mars Fact • Sheet”. National Space Science Data Center. NASA. Re- List of mountains on Mars trieved June 24, 2006. • List of quadrangles on Mars [7] Mallama, A. (2007). “The magnitude ” • and albedo of Mars . Icarus 192 (2): List of rocks on Mars 404–416. Bibcode:2007Icar..192..404M. doi:10.1016/j.icarus.2007.07.011. • List of valles on Mars [8] “What is the typical temperature on Mars?". Astronomy- • Seasonal flows on warm Martian slopes cafe.net. Retrieved August 14, 2012.

• [9] “Mars Exploration Rover Mission: Spotlight”. Marsrover..gov. June 12, 2007. Retrieved August • 2007 WD5—asteroid near-encounter with Mars on 14, 2012. January 30, 2008 [10] Mallama, A. (2011). “Planetary magnitudes”. Sky and • Water on Mars Telescope 121 (1): 51–56. 38 CHAPTER 2. MARS

[11] Barlow, Nadine G. (2008). Mars: an introduction to its [27] Jha, Alok.“Nasa's Curiosity rover finds water in Martian interior, surface and atmosphere. Cambridge planetary soil”. theguardian.com. Retrieved November 6, 2013. science 8. Cambridge University Press. p. 21. ISBN 0-521-85226-9. [28] THE RED PLANET: A SURVEY OF MARS Slide 2 Earth Telescope View of Mars index [12] Krasnopolsky, Vladimir A.; Feldman, Paul D. [29] Peplow, Mark. “How Mars got its rust”. BioEd Online. (2001). “Detection of Molecular Hydrogen MacMillan Publishers Ltd. Retrieved March 10, 2007. in the Atmosphere of Mars”. Science 294 (5548): 1914–1917. Bibcode:2001Sci...294.1914K. [30] NASA – Mars in a Minute: Is Mars Really Red? doi:10.1126/science.1065569. PMID 11729314. (Transcript)

[13] Clancy, R. T.; Sandor, B. J.; Moriarty-Schieven, G. [31] Nimmo, Francis; Tanaka, Ken (2005). “Early H. (2004). “A measurement of the 362 GHz ab- Crustal Evolution Of Mars”. Annual Re- sorption line of Mars atmospheric H2O2”. Icarus view of Earth and Planetary Sciences 33 168 (1): 116–121. Bibcode:2004Icar..168..116C. (1): 133. Bibcode:2005AREPS..33..133N. doi:10.1016/j.icarus.2003.12.003. doi:10.1146/annurev.earth.33.092203.122637.

[14] Formisano, V.; Atreya, S.; Encrenaz, T.; Ig- [32] Rivoldini, A. et al. (June 2011). “Geodesy constraints natiev, N.; Giuranna, M. (2004). “Detection of on the interior structure and composition of Mars”. Methane in the Atmosphere of Mars”. Science 306 Icarus 213 (2): 451–472. Bibcode:2011Icar..213..451R. (5702): 1758–1761. Bibcode:2004Sci...306.1758F. doi:10.1016/j.icarus.2011.03.024. doi:10.1126/science.1101732. PMID 15514118. [33] Jacqué, Dave (September 26, 2003).“APS X-rays reveal [15] “The Lure of Hematite”. Science@NASA. NASA. March secrets of Mars' core”. Argonne National Laboratory. 28, 2001. Retrieved December 24, 2009. Retrieved July 1, 2006.

[16] planet earth and the universe. readers digest. p. 50. [34] Webster, Guy; Brown, Dwayne; Napier, Gary (19 May 2014).“Construction to Begin on 2016 NASA Mars Lan- [17] Yeager, Ashley (July 19, 2008). “Impact May Have der”. NASA. Retrieved 2 April 2015. Transformed Mars”. ScienceNews.org. Retrieved Au- [35] McSween, Harry Y.; Taylor, G. Jeffrey; Wyatt, gust 12, 2008. Michael B. (May 2009). “Elemental Com- [18] Sample, Ian (June 26, 2008). “Cataclysmic impact cre- position of the Martian Crust”. Science 324 ated north-south divide on Mars”. London: Science @ (5928): 736. Bibcode:2009Sci...324..736M. guardian.co.uk. Retrieved August 12, 2008. doi:10.1126/science.1165871. [36] Bandfield, Joshua L. (June 2002).“Global mineral distri- [19] John P. Millis. “Mars Moon Mystery”. butions on Mars”. Journal of Geophysical Research (Plan- [20] Adler, M.; Owen, W. and Riedel, J. (2012). “Use ets) 107 (E6): 9–1. Bibcode:2002JGRE..107.5042B. of MRO Optical Navigation Camera to Prepare for doi:10.1029/2001JE001510. Mars Sample Return”. Concepts and Approaches for [37] Christensen, Philip R. et al. (June 27, 2003). “Mor- Mars Exploration, held June 12–14, 2012 in Houston, phology and Composition of the Surface of Mars: Texas. LPI Contribution No. 1679, id.4337 1679: 4337. Mars Odyssey THEMIS Results”. Science 300 Bibcode:2012LPICo1679.4337A. (5628): 2056–2061. Bibcode:2003Sci...300.2056C. [21] “NASA Images Suggest Water Still Flows in Brief Spurts doi:10.1126/science.1080885. PMID 12791998. on Mars”. NASA/JPL. December 6, 2006. Retrieved [38] Golombek, Matthew P. (June 27, 2003). “The Sur- January 4, 2007. face of Mars: Not Just Dust and Rocks”. Science 300 (5628): 2043–2044. doi:10.1126/science.1082927. [22] “Water ice in crater at Martian north pole”. ESA. July PMID 12829771. 28, 2005. Retrieved March 19, 2010. [39] Tanaka, Kenneth L.;Skinner, James A., Jr.; Dohm, James “ [23] Scientists Discover Concealed at Mid- M.; Irwin, Rossman P., III; Kolb, Eric J.; Fortezzo, Corey ” Latitudes . University of Texas at Austin. November M.; Platz, Thomas; Michael, Gregory G.; Hare, Trent M. 20, 2008. Archived from the original on July 25, 2011. (July 14, 2014).“Geologic Map of Mars - 2014”. USGS. Retrieved March 19, 2010. Retrieved July 22, 2014.

[24] Staff (February 21, 2005). “Mars pictures reveal frozen [40] Krisch, Joshua A. (July 22, 2014). “Brand New Look at sea”. ESA. Retrieved March 19, 2010. the Face of Mars”. New York Times. Retrieved July 22, 2014. [25]“NASA Spacecraft Confirms Martian Water, Mission Ex- tended”. Science @ NASA. July 31, 2008. Retrieved [41] Staff (July 14, 2014). “Mars - Geologic map - Video August 1, 2008. (00:56)". USGS. Retrieved July 22, 2014.

[26] “NASA – NASA Spacecraft Data Suggest Water Flow- [42] Valentine, Theresa; Amde, Lishan (November 9, 2006). ing on Mars”. Nasa.gov. August 4, 2011. Retrieved “Magnetic Fields and Mars”. Mars Global Surveyor @ September 19, 2011. NASA. Retrieved July 17, 2009. 2.14. REFERENCES 39

[43] Neal-Jones, Nancy; O'Carroll, Cynthia. “New Map [57] Kounaves, S. P. et al. (2010). “Wet Chem- Provides More Evidence Mars Once Like Earth”. istry Experiments on the 2007 Phoenix Mars Scout NASA/Goddard Space Flight Center. Retrieved Decem- Lander: Data Analysis and Results”. J. Geophys. ber 4, 2011. Res. 115: E00-E10. Bibcode:2009JGRE..114.0A19K. doi:10.1029/2008JE003084. [44] Halliday, A. N.; Wänke, H.; Birck, J.-L.; Clayton, R. N. (2001). “The Accretion, Composition and [58] Kounaves, S. P. et al. (2010). “Soluble Sulfate Early Differentiation of Mars”. Space Science Reviews in the Martian Soil at the Phoenix Landing Site”. 96 (1/4): 197–230. Bibcode:2001SSRv...96..197H. Icarus 37: L09201. Bibcode:2010GeoRL..37.9201K. doi:10.1023/A:1011997206080. doi:10.1029/2010GL042613.

[45] Zharkov, V. N. (1993). The role of Jupiter in the formation [59] “ Etch-A-Sketch (ESP_013751_1115)". of planets. pp. 7–17. Bibcode:1993GMS....74....7Z. NASA/JPL/University of Arizona. July 2, 2009. Retrieved January 1, 2010. [46] Lunine, Jonathan I.; Chambers, John; Morbidelli, Alessandro; Leshin, Laurie A. (2003). “The ori- [60] Schorghofer, Norbert; Aharonson, Oded; Khati- gin of water on Mars”. Icarus 165 (1): 1– wala, Samar (2002). “Slope streaks on Mars: 8. Bibcode:2003Icar..165....1L. doi:10.1016/S0019- Correlations with surface properties and the poten- 1035(03)00172-6. tial role of water”. Geophysical Research Letters 29 (23): 41–1. Bibcode:2002GeoRL..29w..41S. [47] Barlow, N. G. (October 5–7, 1988). H. Frey, ed. Con- doi:10.1029/2002GL015889. ditions on Early Mars: Constraints from the Cratering [61] Gánti, Tibor et al. (2003). “Dark Record. MEVTV Workshop on Early Tectonic and Vol- Spots: Possible Biomarkers on Mars?". Ori- canic Evolution of Mars. LPI Technical Report 89-04 gins of Life and Evolution of the Biosphere 33 (Easton, Maryland: Lunar and Planetary Institute): 15. (4): 515–557. Bibcode:2003OLEB...33..515G. Bibcode:1989eamd.work...15B. doi:10.1023/A:1025705828948. [48] “Giant Asteroid Flattened Half of Mars, Studies Suggest” [62] NASA Rover Finds Clues to Changes in Mars' Atmo- . Scientific American. Retrieved June 27, 2008. sphere “ [49] Chang, Kenneth (June 26, 2008). Huge Meteor Strike [63] “NASA, Mars: Facts & Figures”. Retrieved January 28, ’ ” Explains Mars s Shape, Reports Say . New York Times. 2010. Retrieved June 27, 2008. [64] Heldmann, Jennifer L. et al. (May 7, 2005). [50] Tanaka, K. L. (1986). “The Stratigraphy of “Formation of Martian gullies by the action of liq- Mars”. Journal of Geophysical Research 91 uid water flowing under current Martian environmen- (B13): E139–E158. Bibcode:1986JGR....91..139T. tal conditions” (PDF). Journal of Geophysical Research doi:10.1029/JB091iB13p0E139. 110 (E5): Eo5004. Bibcode:2005JGRE..11005004H. doi:10.1029/2004JE002261. Retrieved September 17, [51] Hartmann, William K.; , Gerhard 2008. 'conditions such as now occur on Mars, outside (2001). “Cratering Chronology and the Evo- of the temperature-pressure stability regime of liquid wa- lution of Mars”. Space Science Reviews 96 ter'... 'Liquid water is typically stable at the lowest ele- (1/4): 165–194. Bibcode:2001SSRv...96..165H. vations and at low latitudes on the planet because the at- doi:10.1023/A:1011945222010. mospheric pressure is greater than the vapor pressure of water and surface temperatures in equatorial regions can [52] Mitchell, Karl L.; Wilson, Lionel (2003). “Mars: reach 273 K for parts of the day [Haberle et al., 2001]' recent geological activity : Mars: a geologically active planet”. Astronomy & Geophysics 44 (4): 4.16–4.20. [65] Kostama, V.-P.; Kreslavsky, M. A.; Head, J. W. Bibcode:2003A&G....44d..16M. doi:10.1046/j.1468- (June 3, 2006). “Recent high- icy mantle 4004.2003.44416.x. in the northern plains of Mars: Characteristics and ages of emplacement”. Geophysical Research Letters [53] “Mars avalanche caught on camera”. Discovery Channel. 33 (11): L11201. Bibcode:2006GeoRL..3311201K. Discovery Communications. March 4, 2008. Retrieved doi:10.1029/2006GL025946. Retrieved August 12, March 4, 2009. 2007. 'Martian high-latitude zones are covered with a smooth, layered ice-rich mantle'. [54] “Martian soil 'could support life'". BBC News. June 27, 2008. Retrieved August 7, 2008. [66] Byrne, Shane; Ingersoll, Andrew P. (2003).“A Sublima- tion Model for Martian South Polar Ice Features”. Science [55] Chang, Alicia (August 5, 2008).“Scientists: Salt in Mars 299 (5609): 1051–1053. Bibcode:2003Sci...299.1051B. soil not bad for life”. USA Today. . doi:10.1126/science.1080148. PMID 12586939. Retrieved August 7, 2008. [67] “Mars' South Pole Ice Deep and Wide”. NASA. March [56] “NASA Spacecraft Analyzing Martian Soil Data”. JPL. 15, 2007. Archived from the original on April 20, 2009. Retrieved August 5, 2008. Retrieved March 16, 2007. 40 CHAPTER 2. MARS

[68] Whitehouse, David (January 24, 2004).“Long history of [82] “Mars Exploration Rover Mission: Science”. NASA. water and Mars”. BBC News. Retrieved March 20, 2010. July 12, 2007. Retrieved January 10, 2010.

[69] Kerr, Richard A. (March 4, 2005). “Ice or [83] “NASA – NASA Mars Rover Finds Mineral De- Lava Sea on Mars? A Transatlantic Debate posited by Water”. Nasa.gov. December 7, 2011. Re- Erupts”. Science 307 (5714): 1390–1391. trieved August 14, 2012. doi:10.1126/science.307.5714.1390a. PMID 15746395. [84] “Rover Finds“Bulletproof”Evidence of Water on Early [70] Jaeger, W. L. et al. (September 21, 2007). “Athabasca Mars”. News.nationalgeographic.com. December 8, Valles, Mars: A Lava-Draped Channel System”. Science 2011. Retrieved August 14, 2012. 317 (5845): 1709–1711. Bibcode:2007Sci...317.1709J. doi:10.1126/science.1143315. PMID 17885126. [85] “Mars Has “Oceans”of Water Inside?". News.nationalgeographic.com. June 26, 2012. Re- [71] Lucchitta, B. K.; Rosanova, C. E. (August 26, 2003). trieved August 14, 2012. “Valles Marineris; The Grand Canyon of Mars”. USGS. Archived from the original on June 11, 2011. Retrieved [86] Webster, Guy; Brown, Dwayne (March 18, 2013). March 11, 2007. “Curiosity Mars Rover Sees Trend In Water Presence”. NASA. Retrieved March 20, 2013. [72] Murray, John B. et al. (March 17, 2005). “Evidence from the Mars Express High Resolution Stereo Cam- [87] Rincon, Paul (March 19, 2013). “Curiosity breaks rock era for a frozen sea close to Mars' equator”. Nature to reveal dazzling white interior”. BBC. Retrieved March 434 (703): 352–356. Bibcode:2005Natur.434..352M. 19, 2013. doi:10.1038/nature03379. PMID 15772653. [88] Staff (March 20, 2013). “Red planet coughs up a white [73] Craddock, R.A.; Howard, A.D. (2002). rock, and scientists freak out”. MSN. Archived from the “The case for rainfall on a warm, wet early original on March 23, 2013. Retrieved March 20, 2013. Mars”. Journal of Geophysical Research 107 (E11). Bibcode:2002JGRE..107.5111C. [89] Head, J.W. et al. (1999). “Possible An- doi:10.1029/2001JE001505. cient Oceans on Mars: Evidence from Mars Orbiter Laser Altimeter Data”. Science 286 [74] Malin, Michael C.; Edgett, KS (June 30, 2000). (5447): 2134–7. Bibcode:1999Sci...286.2134H. “Evidence for Recent Groundwater Seepage and doi:10.1126/science.286.5447.2134. PMID 10591640. Surface Runoff on Mars”. Science 288 (5475): 2330–2335. Bibcode:2000Sci...288.2330M. [90] Kaufman, Marc (March 5, 2015). “Mars Had an Ocean, doi:10.1126/science.288.5475.2330. PMID 10875910. Scientists Say, Pointing to New Data”. . Retrieved March 5, 2015. [75] “NASA Images Suggest Water Still Flows in Brief Spurts on Mars”. NASA. December 6, 2006. Retrieved Decem- [91] Mellon, J. T.; Feldman, W. C.; Prettyman, T. H. ber 6, 2006. (2003). “The presence and stability of ground ice in the southern hemisphere of Mars”. Icarus [76] “Water flowed recently on Mars”. BBC. December 6, 169 (2): 324–340. Bibcode:2004Icar..169..324M. 2006. Retrieved December 6, 2006. doi:10.1016/j.icarus.2003.10.022.

[77] “Water May Still Flow on Mars, NASA Photo Suggests” [92] “Mars Rovers Spot Water-Clue Mineral, Frost, Clouds”. . NASA. December 6, 2006. Retrieved April 30, 2006. NASA. December 13, 2004. Retrieved March 17, 2006.

[78] Lewis, K.W.; Aharonson, O. (2006). “Stratigraphic [93] Darling, David.“Mars, polar caps”. Encyclopedia of As- analysis of the distributary fan in crater trobiology, Astronomy, and Spaceflight. Retrieved Febru- using stereo imagery”. Journal of Geophysical Re- ary 26, 2007. search 111 (E06001). Bibcode:2006JGRE..11106001L. doi:10.1029/2005JE002558. [94] Malin, M.C.; Caplinger, M.A.; Davis, S.D. (2001). “Observational evidence for an active surface reser- [79] Matsubara, Y.; Howard, A.D.; Drummond, S.A. voir of solid carbon dioxide on Mars”. Science (2011). “Hydrology of early Mars: 294 (5549): 2146–8. Bibcode:2001Sci...294.2146M. basins”. Journal of Geophysical Research 116 doi:10.1126/science.1066416. PMID 11768358. (E04001). Bibcode:2011JGRE..11604001M. doi:10.1029/2010JE003739. [95] “MIRA's Field Trips to the Stars Internet Education Pro- gram”. Mira.or. Retrieved February 26, 2007. [80] “Mineral in Mars 'Berries' Adds to Water Story”(Press release). NASA. March 3, 2004. Archived from the orig- [96] Carr, Michael H. (2003). “Oceans on Mars: An inal on November 9, 2007. Retrieved June 13, 2006. assessment of the observational evidence and pos- sible fate”. Journal of Geophysical Research [81] McEwen, A. S. et al. (September 21, 2007). 108 (5042): 24. Bibcode:2003JGRE..108.5042C. “A Closer Look at Water-Related Geologic doi:10.1029/2002JE001963. Activity on Mars”. Science 317 (5845): 1706–1709. Bibcode:2007Sci...317.1706M. [97] Phillips, Tony. “Mars is Melting, Science at NASA”. doi:10.1126/science.1143987. PMID 17885125. Retrieved February 26, 2007. 2.14. REFERENCES 41

[98] Plaut, J. J et al. (2007). “Subsurface Radar Sounding [114] “Online Atlas of Mars”. Ralphaeschliman.com. Re- of the South Polar Layered Deposits of Mars”. Sci- trieved December 16, 2012. ence 315 (5821): 92–5. Bibcode:2007Sci...316...92P. doi:10.1126/science.1139672. PMID 17363628. [115] “Catalog Page for PIA03467”. Photojour- nal.jpl.nasa.gov. February 16, 2002. Retrieved [99] , Isaac B.; Holt, J. W. (2010).“Onset and migration December 16, 2012. of spiral troughs on Mars revealed by orbital radar”. Na- “ ture 465 (4): 450–453. Bibcode:2010Nature....32..450P. [116] Webster, Guy; Brown, Dwayne (May 22, 2014). NASA ” doi:10.1038/nature09049. Mars Weathercam Helps Find Big New Crater . NASA. Retrieved May 22, 2014. [100] “Mystery Spirals on Mars Finally Explained”. [117] , Shawn (April 4, 2003). “Infrared Analyses of Space.com. May 26, 2010. Retrieved May 26, 2010. Small Impact Craters on Earth and Mars”. University of [101] “NASA Findings Suggest Jets Bursting From Martian Ice Pittsburgh. Archived from the original on June 12, 2007. Cap”. Jet Propulsion Laboratory (NASA). August 16, Retrieved February 26, 2007. 2006. Retrieved August 11, 2009. [118] “Mars Global Geography”. Windows to the Universe. [102] Kieffer, H. H. (2000).“Mars Polar Science 2000”(PDF). University Corporation for Atmospheric Research. April Retrieved September 6, 2009. 27, 2001. Retrieved June 13, 2006.

[103] Portyankina, G., ed. (2006).“Fourth Mars Polar Science [119] Wetherill, G. W. (1999). “Problems Associated Conference” (PDF). Retrieved August 11, 2009. with Estimating the Relative Impact Rates on Mars and the Moon”. Earth, Moon, and Plan- [104] Kieffer, Hugh H.; Christensen, Philip R.; Titus, ets 9 (1–2): 227. Bibcode:1974Moon....9..227W. Timothy N. (May 30, 2006). “CO2 jets formed doi:10.1007/BF00565406. by sublimation beneath translucent slab ice in “ Mars' seasonal south polar ice cap”. Nature 442 [120] Costard, Francois M. (1989). The spa- (7104): 793–796. Bibcode:2006Natur.442..793K. tial distribution of in the Martian hy- ” doi:10.1038/nature04945. PMID 16915284. drolithosphere . Earth, Moon, and Planets 45 (3): 265–290. Bibcode:1989EM&P...45..265C. [105] Sheehan, William. “Areographers”. The Planet Mars: doi:10.1007/BF00057747. A History of Observation and Discovery. Retrieved June [121] Chen, Junyong et al. (2006). “Progress in technology 13, 2006. for the 2005 height determination of Qomolangma Feng [106] Planetary Names: Categories for Naming Features on (Mt. Everest)". Science in China Series D: Earth Sciences Planets and Satellites. Planetarynames.wr.usgs.gov. Re- 49 (5): 531–538. doi:10.1007/s11430-006-0531-1. trieved on December 1, 2011. [122] “Olympus Mons”. mountainprofessor.com. “ ” [107] Viking and the Resources of Mars (PDF). Humans to [123] Glenday, Craig (2009). Guinness World Records. Ran- Mars: Fifty Years of Mission Planning, 1950–2000. Re- dom House, Inc. p. 12. ISBN 0-553-59256-4. trieved March 10, 2007. [124] Wolpert, Stuart (August 9, 2012). “UCLA scientist dis- [108] Frommert, H.; Kronberg, C. “Christiaan Huygens”. covers plate tectonics on Mars”. UCLA. Retrieved Au- SEDS/Lunar and Planetary Lab. Retrieved March 10, gust 13, 2012. 2007. [125] Lin, An (June 4, 2012).“Structural analysis of the Valles [109] Archinal, B. A.; Caplinger, M. (Fall 2002). “Mars, the Marineris zone: Possible evidence for large-scale Meridian, and Mert: The Quest for Martian Longitude” strike-slip faulting on Mars”. 4 (4): 286–330. . Abstract #P22D-06 (American Geophysical Union) 22: Bibcode:2012Lsphe...4..286Y. doi:10.1130/L192.1. Re- 06. Bibcode:2002AGUFM.P22D..06A. trieved October 2, 2012.

[110] NASA (April 19, 2007).“Mars Global Surveyor: MOLA [126] Cushing, G. E.; Titus, T. N.; Wynne, J. J.; Christensen, MEGDRs”. geo.pds.nasa.gov. Retrieved June 24, 2011. P. R. (2007).“Themis Observes Possible Cave Skylights Mars Global Surveyor: MOLA MEGDRs on Mars”(PDF). Lunar and Planetary Science XXXVIII. Retrieved August 2, 2007. [111] Zeitler, W.; Ohlhof, T.; Ebner, H. (2000). “Recompu- tation of the global Mars control-point network”. Pho- [127] “NAU researchers find possible caves on Mars”. Inside togrammetric Engineering & 66 (2): 155– NAU 4 (12) (Northern Arizona University). March 28, 161. Retrieved December 26, 2009. 2007. Retrieved May 28, 2007.

[112] Lunine, Cynthia J. (1999). Earth: evolution of a habitable [128] “Researchers find possible caves on Mars”. Paul Rincon world. Cambridge University Press. p. 183. ISBN 0-521- of BBC News. March 17, 2007. Retrieved May 28, 2007. 64423-2. [129] Jones, Nancy; Steigerwald, Bill; Brown, Dwayne; Web- [113] Morton, Oliver (2002). Mapping Mars: Science, Imagina- ster, Guy (October 14, 2014). “NASA Mission Provides tion, and the Birth of a World. New York: Picador USA. Its First Look at Martian Upper Atmosphere”. NASA. p. 98. ISBN 0-312-24551-3. Retrieved October 15, 2014. 42 CHAPTER 2. MARS

[130] Philips, Tony (2001). “The Solar Wind at Mars”. Sci- [145] Steigerwald, Bill (January 15, 2009). “Martian Methane ence@NASA. Retrieved October 8, 2006. Reveals the Red Planet is not a Dead Planet”. NASA's Goddard Space Flight Center (NASA). Archived from the [131] Multiple Asteroid Strikes May Have Killed Mars’s Mag- original on January 17, 2009. Retrieved January 24, 2009. netic Field [146] “Mars Curiosity Rover News Telecon”. November 2, “ [132] Lundin, R et al. (2004). Solar Wind-Induced 2012. Atmospheric Erosion at Mars: First Results from ASPERA-3 on Mars Express”. Science 305 [147] Kerr, Richard A. (November 2, 2012). “Curiosity Finds (5692): 1933–1936. Bibcode:2004Sci...305.1933L. , or Not”. Science (journal). Retrieved doi:10.1126/science.1101860. PMID 15448263. November 3, 2012.

[133] Bolonkin, Alexander A. (2009). Artificial Environments [148] Wall, Mike (November 2, 2012).“Curiosity Rover Finds on Mars. Berlin Heidelberg: Springer. pp. 599–625. No Methane on Mars —Yet”. Space.com. Retrieved ISBN 978-3-642-03629-3. November 3, 2012. “ [134] Atkinson, Nancy (July 17, 2007). The [149] Chang, Kenneth (November 2, 2012).“Hope of Methane Approach: Getting Large Payloads to the Surface of the on Mars Fades”. New York Times. Retrieved November ” Red Planet . Retrieved September 18, 2007. 3, 2012. [135] Carr, Michael H. (2006). The surface of Mars. Cambridge [150] Webster, Christopher R.; Mahaffy, Paul R.; Atreya, Sushil planetary science series 6 (Cambridge University Press). K.; Flesch, Gregory J.; Farley, Kenneth A. (Septem- p. 16. ISBN 0-521-87201-4. ber 19, 2013). “Low Upper Limit to Methane Abun- [136] “Abundance and Isotopic Composition of Gases in the dance on Mars”. Science. Bibcode:2013Sci...342..355W. Martian Atmosphere from the Curiosity Rover”. Sci- doi:10.1126/science.1242902. Retrieved September 19, encemag.org. July 19, 2013. Retrieved August 19, 2013. 2013.

[137] Lemmon, M. T. et al. (2004). “Atmospheric [151] Cho, Adrian (September 19, 2013). “Mars Rover Finds Imaging Results from Mars Rovers”. Science 306 No Evidence of Burps and Farts”. Science (journal). Re- (5702): 1753–1756. Bibcode:2004Sci...306.1753L. trieved September 19, 2013. doi:10.1126/science.1104474. PMID 15576613. [152] Chang, Kenneth (September 19, 2013). “Mars Rover [138] “Mars Express confirms methane in the Martian atmo- Comes Up Empty in Search for Methane”. New York sphere”. ESA. March 30, 2004. Retrieved March 17, Times. Retrieved September 19, 2013. 2006. [153] “Mars Orbiter Mission – Payloads”. Indian Space Re- [139] Mumma, Michael J. et al. (February 20, 2009). search Organisation (ISRO). ISRO. December 2014. Re- “Strong Release of Methane on Mars in North- trieved 23 December 2014. ern Summer 2003”. Science 323 (5917): 1041–1045. Bibcode:2009Sci...323.1041M. [154] MEPAG Report to the Planetary Science Subcommittee doi:10.1126/science.1165243. PMID 19150811. Author: Jack Mustard, MEPAG Chair. July 9, 2009 (pp. 3) [140] Hand, Eric (October 21, 2008). “Plumes of methane identified on Mars”. Nature News. Retrieved August 2, [155] Webster, Guy; Jones, Nancy Neal; Brown, Dwayne (De- 2009. cember 16, 2014). “NASA Rover Finds Active and An- cient Organic Chemistry on Mars”. NASA. Retrieved De- [141] Krasnopolsky, Vladimir A. (February 2005). “Some cember 16, 2014. problems related to the origin of methane on Mars”. Icarus 180 (2): 359–367. Bibcode:2006Icar..180..359K. [156] Chang, Kenneth (December 16, 2014). "‘A Great Mo- doi:10.1016/j.icarus.2005.10.015. ment’: Rover Finds Clue That Mars May Harbor Life” . New York Times. Retrieved December 16, 2014. [142] Franck, Lefèvre; Forget, François (August 6, 2009).“Ob- served variations of methane on Mars unexplained by [157] Whitehouse, David (July 15, 2004). “Dr. David known atmospheric chemistry and physics”. Nature Whitehouse – Ammonia on Mars could mean life”. 460 (7256): 720–723. Bibcode:2009Natur.460..720L. news.bbc.co.uk (BBC News). Retrieved August 14, 2012. doi:10.1038/nature08228. PMID 19661912. [158] Brown, Dwayne; Neal-Jones, Nancy; Steigerwald, Bill; [143] Oze, C.; Sharma, M. (2005). “Have olivine, will Scott, Jim (18 March 2015). “NASA Spacecraft De- gas: Serpentinization and the abiogenic production of tects Aurora and Mysterious Dust Cloud around Mars”. methane on Mars”. Geophysical Research Letters NASA. Release 15-045. Retrieved 18 March 2015. 32 (10): L10203. Bibcode:2005GeoRL..3210203O. doi:10.1029/2005GL022691. [159] “Mars' desert surface...”. MGCM Press release. NASA. Retrieved February 25, 2007. [144] Tenenbaum, David (June 9, 2008). “Making Sense of Mars Methane”. Astrobiology Magazine. Archived from [160] Kluger, Jeffrey (September 1, 1992). “Mars, in Earth's the original on September 23, 2008. Retrieved October 8, Image”. Discover Magazine. Retrieved November 3, 2008. 2009. 2.14. REFERENCES 43

[161] Goodman, Jason C (September 22, 1997). “The Past, [178] Peplow, Mark (February 25, 2005). “Formalde- Present, and Possible Future of Martian Climate”. MIT. hyde claim inflames Martian debate”. Nature. Archived from the original on November 10, 2010. Re- doi:10.1038/news050221-15. trieved February 26, 2007. [179] “DLR – Surviving the conditions on Mars (26 April [162] Philips, Tony (July 16, 2001). “Planet Gobbling Dust 2012)". Dlr.de. April 26, 2012. Retrieved December Storms”. Science @ NASA. Retrieved June 7, 2006. 16, 2012.

[163] “Mars 2009/2010”. Students for the Exploration and [180] “MSL Science Corner: Rover Environmental Monitoring Development of Space (SEDS). May 6, 2009. Retrieved Station (REMS)". NASA/JPL. Retrieved September 9, December 28, 2007. 2009. [164] “Mars distance from the Sun from January 2011 to Jan- [181] “Mars Science Laboratory Fact Sheet”. NASA/JPL. uary 2015”. Retrieved January 27, 2012. Retrieved June 20, 2011. [165] Vitagliano, Aldo (2003).“Mars' Orbital eccentricity over [182] “NASA's Mars Odyssey Shifting Orbit for Extended Mis- time”. Solex. Universita' degli Studi di Napoli Federico sion”. NASA. October 9, 2008. Retrieved November 15, II. Retrieved July 20, 2007. 2008. [166] Meeus, Jean (March 2003). “When Was Mars Last This Close?". International Planetarium Society. Archived [183] “Mars Science Laboratory —Homepage”. NASA. from the original on May 16, 2011. Retrieved January Archived from the original on July 30, 2009. 18, 2008. [184] “Chemistry and Cam (ChemCam)". NASA. [167] Baalke, Ron (August 22, 2003). “Mars Makes Closest “ ” Approach In Nearly 60,000 Years”. meteorite-list. Re- [185] Curiosity Mars rover takes historic drill sample . BBC. trieved January 18, 2008. February 10, 2013. Retrieved February 10, 2013.

[168] Nowack, Robert L. “Estimated Habitable Zone for the [186] “ISRO: Mars Orbiter Mission”. isro.gov.in. Solar System”. Department of Earth and Atmospheric [187] “Deimos”. Planetary Societies's Explore the Cosmos. Sciences at Purdue University. Retrieved April 10, 2009. Archived from the original on June 5, 2011. Retrieved [169] , Helen (February 15, 2008).“Early Mars 'too salty' June 13, 2006. for life”. BBC News. Retrieved February 16, 2008. [188] Bertaux, Jean-Loup et al. (June 9, 2005). “Dis- [170] Hannsson, (1997). Mars and the Development of covery of an aurora on Mars”. Nature 435 Life. Wiley. ISBN 0-471-96606-1. (7043): 790–4. Bibcode:2005Natur.435..790B. doi:10.1038/nature03603. PMID 15944698. [171] “New Analysis of Viking Mission Results Indicates Pres- ence of Life on Mars”. Physorg.com. January 7, 2007. [189] Meeus, J.; Goffin, E. (1983). “Transits of Earth as seen Retrieved March 2, 2007. from Mars”. Journal of the British Astronomical Associ- ation 93 (3): 120–123. Bibcode:1983JBAA...93..120M. [172] “Phoenix Returns Treasure Trove for Science”. NASA/JPL. June 6, 2008. Retrieved June 27, 2008. [190] , J. F., III et al. (July 7, 2005).“Solar eclipses of Pho- ” [173] Bluck, John (July 5, 2005). “NASA Field-Tests the First bos and Deimos observed from the surface of Mars . Na- System Designed to Drill for Subsurface Martian Life”. ture 436 (7047): 55–57. Bibcode:2005Natur.436...55B. NASA. Retrieved January 2, 2010. doi:10.1038/nature03437. PMID 16001060.

[174] Kounaves, S. P. et al., Evidence of martian perchlorate, [191] Staff (March 17, 2004). “Martian Moons Block chlorate, and nitrate in Mars meteorite EETA79001: im- Sun In Unique Eclipse Images From Another Planet”. plications for oxidants and organics, Icarus, 2014, 229, SpaceDaily. Retrieved February 13, 2010. 206-213, doi:10.1016/j.icarus.2013.11.012, [192] Webster, Guy; Brown, Dwayne; Jones, Nancy; Steiger- [175] Kounaves, S. P. et al. (2014). ", Identification of wald, Bill (October 19, 2014). “All Three NASA Mars the perchlorate parent salts at the Phoenix Mars land- Orbiters Healthy After Comet Flyby”. NASA. Retrieved ing site and implications”. Icarus 232: 226–231. October 20, 2014. doi:10.1016/j.icarus.2014.01.016. [193] Agence France-Presse (October 19, 2014). “A Comet's [176] Golden, D. C. et al. (2004). “Evidence for exclusively Brush With Mars”. New York Times. Retrieved October inorganic formation of magnetite in Martian meteorite 20, 2014. ALH84001”. American Mineralogist 89 (5–6): 681–695. Retrieved December 25, 2010. [194] Denis, Michel (October 20, 2014). “Spacecraft in great shape – our mission continues”. European Space Agency. [177] Krasnopolsky, Vladimir A.; Maillard, Jean-Pierre; Owen, Retrieved October 21, 2014. Tobias C. (2004). “Detection of methane in the Martian atmosphere: evidence for life?". Icarus [195] Staff (October 21, 2014). “I'm safe and sound, tweets 172 (2): 537–547. Bibcode:2004Icar..172..537K. MOM after comet sighting”. The Hindu. Retrieved Oc- doi:10.1016/j.icarus.2004.07.004. tober 21, 2014. 44 CHAPTER 2. MARS

[196] Moorhead, Althea; Wiegert, Paul A.; Cooke, William [212] Needham, Joseph; Ronan, Colin A. (1985). The Shorter J. (December 1, 2013). “The flu- Science and Civilisation in China: An Abridgement of ence at Mars due to comet C/2013 A1 (Siding Joseph Needham's Original Text. The shorter science and Spring)". Icarus. Bibcode:2014Icar..231...13M. civilisation in China 2 (3rd ed.) (Cambridge University doi:10.1016/j.icarus.2013.11.028. Retrieved December Press). p. 187. ISBN 0-521-31536-0. 7, 2013. [213] Thompson, Richard (1997).“Planetary Diameters in the [197] Grossman, Lisa (December 6, 2013). “Fiercest meteor Surya-Siddhanta”. Journal of Scientific Exploration 11 shower on record to hit Mars via comet”. New Scientist. (2): 193–200 [193–6]. Retrieved March 13, 2010. Retrieved December 7, 2013. [214] ‹The template Chinaplanetnames is being considered for [198] Lloyd, John; John Mitchinson (2006). The QI Book of deletion.› General Ignorance. Britain: Faber and Faber Limited. pp. China: De Groot, Jan Jakob Maria (1912). Religion in 102, 299. ISBN 978-0-571-24139-2. China: universism. a key to the study of Taoism and Con- fucianism. American lectures on the history of religions 10 [199] Peck, Akkana. “Mars Observing FAQ”. Shallow Sky. (G. P. Putnam's Sons). p. 300. Retrieved 2010-01-08. Retrieved June 15, 2006. Japan: Crump, Thomas (1992). The Japanese numbers game: the use and understanding of numbers in modern [200] Zeilik, Michael (2002). Astronomy: the Evolving Universe Japan. Nissan Institute/Routledge Japanese studies series (9th ed.). Cambridge University Press. p. 14. ISBN 0- (Routledge). pp. 39–40. ISBN 0415056098. 521-80090-0. Korea: Hulbert, Homer Bezaleel (1909). The passing of [201] Jacques Laskar (August 14, 2003). “Primer on Mars op- Korea. Doubleday, Page & company. p. 426. Retrieved positions”. IMCCE, . Retrieved Octo- 2010-01-08. ber 1, 2010. (Solex results) [215] Taton, Reni (2003). Reni Taton, Wilson and [202]“Close Encounter: Mars at Opposition”. NASA. Novem- Michael Hoskin, ed. Planetary Astronomy from the Re- ber 3, 2005. Retrieved March 19, 2010. naissance to the Rise of Astrophysics, Part A, Tycho Brahe to . Cambridge University Press. p. 109. ISBN [203] Sheehan, William (February 2, 1997).“Appendix 1: Op- 0-521-54205-7. positions of Mars, 1901—2035”. The Planet Mars: A History of Observation and Discovery. University of Ari- [216] Hirshfeld, Alan (2001). Parallax: the race to measure the zona Press. Retrieved January 30, 2010. cosmos. Macmillan. pp. 60–61. ISBN 0-7167-3711-6. “ [204] The opposition of February 12, 1995 was followed by one [217] Breyer, Stephen (1979). Mutual Occultation ” on March 17, 1997. The opposition of July 13, 2065 will of Planets . Sky and Telescope 57 (3): 220. be followed by one on October 2, 2067. Astropro 3000- Bibcode:1979S&T....57..220A. year Sun-Mars Opposition Tables [218] Peters, W. T. (1984). “The Appearance of Venus and Mars in 1610”. Journal of the 15 [205] Rao, Joe (August 22, 2003). “NightSky Friday—Mars (3): 211–214. Bibcode:1984JHA....15..211P. and Earth: The Top 10 Close Passes Since 3000 B.C.”. Space.com. Archived from the original on May 20, 2009. [219] Sheehan, William (1996). “2: Pioneers”. The Planet Retrieved June 13, 2006. Mars: A History of Observation and Discovery. ua- press.arizona.edu (Tucson: University of Arizona). Re- [206] Novakovic, B. (2008). “Senenmut: An Ancient Egyp- trieved January 16, 2010. tian Astronomer”. Publications of the Astronomical Observatory of Belgrade 85: 19–23. arXiv:0801.1331. [220] Snyder, Dave (May 2001).“An Observational History of Bibcode:2008POBeo..85...19N. Mars”. Retrieved February 26, 2007.

[207] North, John David (2008). Cosmos: an illustrated history [221] Sagan, Carl (1980). Cosmos. New York City: Random of astronomy and cosmology. University of Chicago Press. House. p. 107. ISBN 0-394-50294-9. pp. 48–52. ISBN 0-226-59441-6. [222] Basalla, George (2006). “Percival Lowell: Champion [208] Swerdlow, Noel M. (1998). “Periodicity and Variability of Canals”. Civilized Life in the Universe: Scientists on of Synodic Phenomenon”. The Babylonian theory of the Intelligent Extraterrestrials. Oxford University Press US. planets. Princeton University Press. pp. 34–72. ISBN pp. 67–88. ISBN 0-19-517181-0. 0-691-01196-6. [223] Maria, K.; Lane, D. (2005). “Geographers of Mars” [209] Poor, Charles Lane (1908). The solar system: a study . Isis 96 (4): 477–506. doi:10.1086/498590. PMID of recent observations. Science series 17 (G. P. Putnam's 16536152. sons). p. 193. [224] Perrotin, M. (1886).“Observations des canaux de Mars” [210] Harland, David Michael (2007). "Cassini at Saturn: Huy- . Bulletin Astronomique, Serie I (in French) 3: 324–329. gens results". p. 1. ISBN 0-387-26129-X Bibcode:1886BuAsI...3..324P.

[211] Hummel, Charles E. (1986). The Galileo connection: re- [225] Zahnle, K. (2001). “Decline and fall of the solving conflicts between science & the Bible. InterVarsity Martian empire”. Nature 412 (6843): 209–213. Press. pp. 35–38. ISBN 0-87784-500-X. doi:10.1038/35084148. PMID 11449281. 2.15. EXTERNAL LINKS 45

[226] Salisbury, F. B. (1962). “Martian Biology”. Science [244] “Close Inspection for Phobos”. ESA website. Retrieved 136 (3510): 17–26. Bibcode:1962Sci...136...17S. June 13, 2006. doi:10.1126/science.136.3510.17. JSTOR 1708777. PMID 17779780. [245]“Ares Attendants: Deimos & Phobos”. Greek Mythology. Retrieved June 13, 2006. [227] Ward, Peter Douglas; Brownlee, Donald (2000). Rare earth: why complex life is uncommon in the universe. [246] Hunt, G. E.; Michael, W. H.; Pascu, D.; Veverka, Copernicus Series (2nd ed.) (Springer). p. 253. ISBN J.; Wilkins, G. A.; Woolfson, M. (1978). “The 0-387-95289-6. Martian satellites —100 years on”. Quarterly Jour- nal of the Royal Astronomical Society 19: 90–109. [228] , Peter (2007). Distant worlds: milestones in plan- Bibcode:1978QJRAS..19...90H. etary exploration. Copernicus Series (Springer). p. 119. ISBN 0-387-40212-8. [247] “Greek Names of the Planets”. Archived from the orig- inal on May 9, 2010. Retrieved July 14, 2012. Aris is the [229] Dinerman, Taylor (September 27, 2004). “Is the Great Greek name of the planet Mars, the fourth planet from the Galactic Ghoul losing his appetite?". The space review. sun, also known as the Red planet. Aris or Ares was the Retrieved March 27, 2007. Greek god of War. See also the Greek article about the planet. [230] “Percivel Lowell's Canals”. Retrieved March 1, 2007.

[231] Fergus, Charles (2004). “Mars Fever”. Research/Penn [248] Arnett, Bill (November 20, 2004).“Phobos”. nineplan- State 24 (2). Retrieved August 2, 2007. ets. Retrieved June 13, 2006.

[232] Tesla, Nikola (February 19, 1901). “Talking with the [249] Ellis, Scott. “Geological History: Moons of Mars”. Planets”. Collier's Weekly. Retrieved May 4, 2007. CalSpace. Archived from the original on May 17, 2007. Retrieved August 2, 2007. [233] Cheney, (1981). Tesla, man out of time. Engle- wood Cliffs, New Jersey: Prentice-Hall. p. 162. ISBN [250] Andert, T. P.; Rosenblatt, P.; Pätzold, M.; Häusler, 978-0-13-906859-1. OCLC 7672251. B.; Dehant, V.; Tyler, G. L.; Marty, J. C. (May 7, 2010). “Precise mass determination and the na- [234]“Departure of Lord Kelvin”. The New York Times. May ture of Phobos”. Geophysical Research Letters 37 11, 1902. p. 29. (L09202): L09202. Bibcode:2010GeoRL..3709202A. doi:10.1029/2009GL041829. [235] Pickering, Edward Charles (January 16, 1901). “The Light Flash From Mars” (PDF). The New York Times. [251] Giuranna, M.; Roush, T. L.; Duxbury, T.; Hogan, R. C.; Archived from the original on June 5, 2007. Retrieved Geminale, A.; Formisano, V. (2010). Compositional In- May 20, 2007. terpretation of PFS/MEx and TES/MGS Thermal Infrared Spectra of Phobos. European Planetary Science Congress [236] Fradin, Dennis Brindell (1999). Is There Life on Mars?. Abstracts, Vol. 5. Retrieved October 1, 2010. McElderry Books. p. 62. ISBN 0-689-82048-8. “ [237] Lightman, Bernard V. (1997). Victorian Science in Con- [252] Mars Moon Phobos Likely Forged by Catastrophic ” text. University of Chicago Press. pp. 268–273. ISBN Blast . Space.com. September 27, 2010. Retrieved Oc- 0-226-48111-5. tober 1, 2010.

[238] Lubertozzi, Alex; Holmsten, Brian (2003). The war of the [253] “M. Adler, et al. – Use of MRO Optical Navigation Cam- worlds: Mars' invasion of earth, inciting panic and inspir- era .. (2012)" (PDF). lpi.usra.edu. Retrieved December ing terror from H.G. Wells to Orson Welles and beyond. 16, 2012. Sourcebooks, Inc. pp. 3–31. ISBN 1-57071-985-3.

[239] Schwartz, Sanford (2009). C. S. Lewis on the Final Fron- tier: Science and the Supernatural in the Space Trilogy. 2.15 External links Oxford University Press US. pp. 19–20. ISBN 0-19- 537472-X. • Mars at DMOZ

[240] Buker, Derek M. (2002). The science fiction and fantasy • readers' advisory: the librarian's guide to cyborgs, aliens, and sorcerers. ALA readers' advisory series. ALA Edi- • On Mars: Exploration of the Red Planet 1958–1978 tions. p. 26. ISBN 0-8389-0831-4. from the NASA History Office.

[241] Darling, David.“Swift, Jonathan and the moons of Mars” • Mars Unearthed at the Wayback Machine (archived . Retrieved March 1, 2007. April 16, 2001)—Comparisons of terrains between [242] Rabkin, Eric S. (2005). Mars: a tour of the human imag- Earth and Mars ination. Greenwood Publishing Group. pp. 141–142. • ISBN 0-275-98719-1. Be on Mars—Anaglyphs from the Mars Rovers (3D)

[243] Miles, Kathy; Peters II, Charles F.“Unmasking the Face” • Mars articles in Planetary Science Research Discov- . StarrySkies.com. Retrieved March 1, 2007. eries 46 CHAPTER 2. MARS

• Geody Mars—World's search engine that supports NASA World Wind, Celestia, and other applications • —The Mars Society, an international organization dedicated to the study, exploration, and settlement of Mars.

• New Papers about Martian Geomorphology • How far is it to Mars?

Media

• Video – Mars (National Oceanic and Atmospheric Administration). • Video (04:32) – Evidence for “Vigorously”Flow- ing Water on Ancient Mars (September 2012). on YouTube

• Panoramic View of Gale Crater on Mars (4 billion pixels) (March, 2013).

• Panoramic Views of Mars (Curiosity rover 1 and Curiosity rover 2).

• Computer Simulated Flight into Mariner . • 3D-Flight into Mariner Valley.

• Mars at the Wayback Machine (archived January 5, 2008) Astronomy Cast episode #52, includes full transcript.

• 15 Amazing Pictures of the Red Planet – slideshow at The Huffington Post.

• Storm Front. • Buried basins.

• Dunes. source. • Mars. source.

Cartographic resources

• Mars and Mars map with feature names from the USGS page • PDS Map-a-planet

• Viking Photomap • MOLA (topographic) map

• 3D maps of Mars in NASA World Wind • Google Mars—Interactive image of Mars

• Mars - Geologic Map (USGS, 2014) (original / crop / full / video (00:56)). Chapter 3

Mercury

Mercury or The Mercury may refer to: 3.4 Transportation

• Mercury (automobile), a marque of automobile pro- 3.1 Common meanings duced by the Ford Motor Company (1938–2011) • Mercury (cyclecar), an American cyclecar from 1914 • Mercury (element), a metallic • Mercury (train), a family of New York Central • Mercury (planet), the planet closest to the Sun streamliner passenger trains (1936–1958) • Blackburn Mercury, British aircraft from 1911 • Mercury (mythology), a Roman god • Bristol Mercury, a 9-cylinder aircraft engine • Russian brig Mercury, Russian warship 3.2 Places • Mercury, Shuttle America's callsign • Mercury Marine, a major manufacturer of marine • Mercury Bay, on the North Island of New Zealand engines, particularly outboard motors • Mercury Islands, a group of islands off the northeast coast of New Zealand 3.5 In entertainment • Mercury, Nevada, a closed city within the Nevada Test Site, United States 3.5.1 Music

• Mercury, Savoie, a commune in southeastern France • Mercury Records, a • Freddie Mercury, the frontman for the rock group Queen 3.3 In the military • Daniela Mercury, Brazilian singer, and • Operation Mercury, codename for the German in- • Mercury (Longview album) vasion of Crete during World War II • Mercury (American Music Club album) • HMS Mercury, the name of several ships of the • Mercury (Madder Mortem album) Royal Navy • “Mercury”(song), a 2008 song by Bloc Party • USS Mercury, the name of several ships of the •“Mercury”, a song by Kathleen Edwards from Failer United States Navy •“Mercury”, a song by Counting Crows from • Boeing E-6 Mercury, an American airborne com- Recovering the Satellites mand post and communications relay introduced in •“Mercury, the Winged Messenger”, a movement in 1989 Gustav 's The Planets • Miles Mercury, a British aircraft designed during the • Mercury Prize, an annual music prize awarded for Second World War the best album from the United Kingdom

47 48 CHAPTER 3. MERCURY

3.5.2 Comics 3.7 Sports

• Mercury (Marvel Comics), a Marvel Comics char- • Edmonton Mercurys, a 1940s and 50s intermediate acter who can turn herself into a mercurial substance ice hockey team from Canada • Mercury (Amalgam Comics), a combination of the • Phoenix Mercury, a Women's National Basketball characters Impulse and Quicksilver Association team from Arizona, United States • Makkari (comics) or Mercury, an Eternal • Toledo Mercurys, a defunct International Hockey • Mercury, a member of the Metal Men, a DC comics League franchise from Ohio, United States team • Mercury, a member of Cerebro's X-Men 3.8 Publications

3.5.3 Other • Mercury (magazine), an astronomy magazine • Mercury (newspaper), a list • Mercury (TV series), an Australian TV series launched in 1996 • Mercury (novel), a 2005 novel by Ben Bova 3.9 Radio stations • Sailor Mercury, a character in the Sailor Moon fran- • chise 102.7 Mercury FM, a radio station in Surrey, United Kingdom • Archer Maclean's Mercury, the first in a series of games developed and/or published by Ignition En- • Mercury 96.6, a radio station in Hertfordshire, tertainment United Kingdom

3.6 Technology 3.10 In business

• , the first human spaceflight pro- • Mercury Communications, a British telecommuni- gram of the United States cations firm set up in the 1980s

• Mercury (satellite), a series of three American satel- • Mercury Insurance Group, an American automobile lites and property insurance company

• Mercury (cipher machine), a British cipher machine • The Mercury Mall, a shopping centre in Romford, used from the 1950s England

• The Mercury Award, an international airline award 3.6.1 Computing for in-flight catering

• Mercury Interactive, software testing tools vendor

• Mercury (programming language), a func- 3.11 Other uses tional/logical programming language based on Prolog • Mercury (name), a given name and

• Mercury OS, a real-time operating system for em- • Mercury dime, a United States coin minted from bedded systems 1916 through 1945

• Ferranti Mercury, an early 1950s commercial com- • Mercury (plant), members of the plant genus Mer- puter curialis

• Mercury Autocode, a programming language for the • Mercury Boulevard, a road in Virginia, United Ferranti Mercury computer States

• Mercury Mail Transport System, a standards- • Mercury Fountain, a fountain in Tom Quad, Christ compliant donationware mail server Church College, Oxford, England 3.12. SEE ALSO 49

3.12 See also

• Mercur (disambiguation)

• Mercurius (disambiguation) • Mercury 1 (disambiguation)

• Mercury 2 (disambiguation)

• Mercury 3 (disambiguation) • Mercury 4 (disambiguation)

• Mercury House (disambiguation) • Mercury program (disambiguation) Chapter 4

Neptune

This article is about the planet. For other uses, see weather patterns. For example, at the time of the 1989 Neptune (disambiguation). flyby, the planet's southern hemisphere had a comparable to the Great Red Spot on Jupiter. These weather patterns are driven by the Neptune is the eighth and farthest planet from the Sun in the Solar System. It is the fourth-largest planet by diam- strongest sustained winds of any planet in the Solar Sys- tem, with recorded wind speeds as high as 2,100 kilome- eter and the third-largest by mass. Among the gaseous * planets in the Solar System, Neptune is the most dense. tres per hour (1,300 mph). [15] Because of its great dis- tance from the Sun, Neptune's outer atmosphere is one Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the of the coldest places in the Solar System, with tempera- mass of Earth, and not as dense as Neptune.*[lower-alpha tures at its cloud tops approaching 55 K (−218 °C). Tem- peratures at the planet's centre are approximately 5,400 3] Neptune orbits the Sun at an average distance of 30.1 * * astronomical units. Named after the Roman god of the K (5,100 °C). [16] [17] Neptune has a faint and frag- “ ” sea, its astronomical symbol is ♆, a stylised version of the mented ring system (labelled arcs ), which may have god Neptune's . been detected during the 1960s but was indisputably con- firmed only in 1989 by Voyager 2.*[18] Neptune was the first and only planet found by mathemat- ical prediction rather than by empirical observation. Un- expected changes in the orbit of Uranus led Alexis Bou- vard to deduce that its orbit was subject to gravitational 4.1 History by an unknown planet. Neptune was subse- * quently observed on 23 September 1846 [1] by Johann 4.1.1 Discovery within a degree of the position predicted by , and its largest moon, , was discovered shortly thereafter, though none of the planet's remaining Main article: 13 moons were located telescopically until the 20th cen- tury. Neptune was visited by Voyager 2, when it flew by Some of the earliest recorded observations ever made the planet on 25 August 1989.*[10] through a telescope, Galileo's drawings on 28 December Neptune is similar in composition to Uranus, and both 1612 and 27 January 1613, contain plotted points that have compositions that differ from those of the larger gas match up with what is now known to be the position of giants, Jupiter and Saturn. Neptune's atmosphere, like Neptune. On both occasions, Galileo seems to have mis- — Jupiter's and Saturn's, is composed primarily of hydrogen taken Neptune for a fixed star when it appeared close — * and helium, along with traces of hydrocarbons and possi- in conjunction to Jupiter in the night sky; [19] hence, bly nitrogen; it contains a higher proportion of“”such he is not credited with Neptune's discovery. At his first as water, ammonia, and methane. Astronomers some- observation in December 1612, Neptune was almost sta- times categorise Uranus and Neptune as "ice giants" to tionary in the sky because it had just turned retrograde emphasise this distinction.*[11] The interior of Neptune, that day. This apparent backward motion is created when like that of Uranus, is primarily composed of ices and Earth's orbit takes it past an outer planet. Because Nep- rock.*[12] Perhaps the core has a solid surface, but the tune was only beginning its yearly retrograde cycle, the motion of the planet was far too slight to be detected with temperature would be thousands of degrees and the at- * mospheric pressure crushing.*[13] Traces of methane in Galileo's small telescope. [20] In July 2009, University the outermost regions in part account for the planet's blue of Melbourne physicist David Jamieson announced new appearance.*[14] evidence suggesting that Galileo was at least aware that the star he had observed had moved relative to the fixed In contrast to the hazy, relatively featureless atmosphere stars.*[21] of Uranus, Neptune's atmosphere has active and visible In 1821, Alexis Bouvard published astronomical ta-

50 4.1. HISTORY 51

bles of the orbit of Neptune's neighbour Uranus.*[22] planet), failing to identify it owing to his casual approach Subsequent observations revealed substantial deviations to the work.*[23]*[27] from the tables, leading Bouvard to hypothesize that In the wake of the discovery, there was much nation- an unknown body was perturbing the orbit through * alistic rivalry between the French and the British over gravitational interaction. [23] In 1843, John Couch who deserved credit for the discovery. Eventually an in- Adams began work on the orbit of Uranus using the ternational consensus emerged that both Le Verrier and data he had. Via Cambridge Observatory director James Adams jointly deserved credit. Since 1966 Dennis Rawl- , he requested extra data from Sir George Airy, ins has questioned the credibility of Adams's claim to the Astronomer Royal, who supplied it in February 1844. co-discovery, and the issue was re-evaluated by histori- Adams continued to work in 1845–46 and produced sev- ans with the return in 1998 of the “Neptune papers” eral different estimates of a new planet.*[24]*[25] (historical documents) to the Royal Observatory, - wich.*[28] After reviewing the documents, they suggest that “Adams does not deserve equal credit with Le Ver- rier for the discovery of Neptune. That credit belongs only to the person who succeeded both in predicting the planet's place and in convincing astronomers to search for it.”*[29]

4.1.2 Naming

Shortly after its discovery, Neptune was referred to sim- ply as “the planet exterior to Uranus”or as “Le Ver- rier's planet”. The first suggestion for a name came from Galle, who proposed the name . In England, Challis put forward the name .*[30] Claiming the right to name his discovery, Le Verrier quickly proposed the name Neptune for this new planet, though falsely stating that this had been officially ap- proved by the French Bureau des .*[31] In Oc- tober, he sought to name the planet Le Verrier, after him- self, and he had loyal support in this from the observatory Urbain Le Verrier director, François . This suggestion met with stiff resistance outside France.*[32] French almanacs quickly In 1845–46, Urbain Le Verrier, independently of Adams, developed his own calculations but aroused no enthusi- reintroduced the name Herschel for Uranus, after that planet's discoverer Sir , and Leverrier asm in his compatriots. In June 1846, upon seeing Le * Verrier's first published estimate of the planet's longitude for the new planet. [33] and its similarity to Adams's estimate, Airy persuaded Struve came out in favour of the name Neptune on 29 De- Challis to search for the planet. Challis vainly scoured cember 1846, to the Saint Petersburg Academy of Sci- the sky throughout August and September.*[23]*[26] ences.*[34] Soon Neptune became the internationally ac- Meanwhile, Le Verrier by letter urged Berlin Observatory cepted name. In Roman mythology, Neptune was the god astronomer to search with the ob- of the sea, identified with the Greek . The de- servatory's refractor. Heinrich d'Arrest, a student at the mand for a mythological name seemed to be in keeping observatory, suggested to Galle that they could compare with the nomenclature of the other planets, all of which, except for Earth, were named for deities in Greek and a recently drawn chart of the sky in the region of Le Ver- * rier's predicted location with the current sky to seek the Roman mythology. [35] displacement characteristic of a planet, as opposed to a Most languages today, even in countries that have no di- fixed star. On the evening of 23 September 1846, the day rect to Greco-Roman culture, use some variant of the Galle received the letter, Neptune was discovered within name “Neptune”for the planet; in Chinese, Japanese 1° of where Le Verrier had predicted it to be, and about and Korean, the planet's name was translated as “sea 12° from Adams' prediction. Challis later realised that king star”(海王星), because Neptune was the god of the he had observed the planet twice in August (Neptune had sea.*[36] In modern Greek, though, the planet is called been observed on 8 and 12 August, but because Challis Poseidon (Ποσειδώνας: Poseidonas), the Greek counter- lacked an up-to-date star map it was not recognised as a part to Neptune.*[37] 52 CHAPTER 4. NEPTUNE

4.1.3 Status concentrations of methane, ammonia and water are found in the lower regions of the atmosphere.*[16] From its discovery in 1846 until the subsequent discovery of Pluto in 1930, Neptune was known planet. Upon Pluto's discovery Neptune became the penulti- mate planet, save for a 20-year period between 1979 and 1999 when Pluto's elliptical orbit brought it closer to the Sun than Neptune.*[38] The discovery of the Kuiper belt in 1992 led many astronomers to debate whether Pluto should be considered a planet in its own right or part of the belt's larger structure.*[39]*[40] In 2006, the International Astronomical Union defined the word “planet”for the first time, reclassifying Pluto as a "" and making Neptune once again the last planet in the Solar System.*[41]

4.2 Composition and structure The internal structure of Neptune: 1. Upper atmosphere, top clouds 2. Atmosphere consisting of hydrogen, helium and methane gas 3. Mantle consisting of water, ammonia and methane ices 4. Core consisting of rock (silicates and nickel–iron)

The mantle is equivalent to 10 to 15 Earth masses and is rich in water, ammonia and methane.*[1] As is cus- tomary in planetary science, this mixture is referred to as icy even though it is a hot, dense fluid. This fluid, which has a high electrical conductivity, is sometimes called a water–ammonia ocean.*[45] The mantle may consist of a layer of ionic water in which the water molecules break down into a soup of hydrogen and oxygen ions, and deeper down superionic water in which the oxygen crys- tallises but the hydrogen ions float around freely within the oxygen lattice.*[46] At a depth of 7000 km, the con- A size comparison of Neptune and Earth ditions may be such that methane decomposes into - mond crystals that rain downwards like hailstones.*[47] Neptune's mass of 1.0243×1026 kg,*[6] is intermediate Very-high-pressure experiments at the Lawrence Liver- between Earth and the larger gas giants: it is 17 times more National Laboratory suggest that the base of the that of Earth but just 1/19th that of Jupiter.*[lower-alpha mantle may comprise an ocean of liquid diamond, with * * 4] Its is surpassed only by Jupiter.*[42] floating solid 'diamond-bergs'. [48] [49] Neptune's equatorial radius of 24,764 km*[8] is nearly The core of Neptune is composed of iron, nickel and four times that of Earth. Neptune and Uranus are of- silicates, with an interior model giving a mass about 1.2 ten considered a subclass of gas giant termed "ice gi- times that of Earth.*[50] The pressure at the centre is 7 ants", due to their smaller size and higher concentrations Mbar (700 GPa), about twice as high as that at the centre of volatiles relative to Jupiter and Saturn.*[43] In the of Earth, and the temperature may be 5,400 K.*[16]*[17] search for extrasolar planets Neptune has been used as a metonym: discovered bodies of similar mass are often referred to as“”,*[44] just as astronomers refer 4.2.2 Atmosphere to various extra-solar bodies as “”. At high altitudes, Neptune's atmosphere is 80% hydrogen and 19% helium.*[16] A trace amount of methane is 4.2.1 Internal structure also present. Prominent absorption bands of methane occur at wavelengths above 600 nm, in the red and in- Neptune's internal structure resembles that of Uranus. Its frared portion of the . As with Uranus, this ab- atmosphere forms about 5% to 10% of its mass and ex- sorption of red light by the atmospheric methane is part tends perhaps 10% to 20% of the way towards the core, of what gives Neptune its blue hue,*[51] although Nep- where it reaches pressures of about 10 GPa, or about tune's vivid azure differs from Uranus's milder cyan. Be- 100,000 times that of Earth's atmosphere. Increasing cause Neptune's atmospheric methane content is similar 4.2. COMPOSITION AND STRUCTURE 53

found at pressures of about 50 bars (5.0 MPa), where the temperature reaches 273 K (0 °C). Underneath, clouds of ammonia and hydrogen sulfide may be found.*[52] High-altitude clouds on Neptune have been observed casting shadows on the opaque cloud deck below. There are also high-altitude cloud bands that wrap around the planet at constant latitude. These circumferential bands have widths of 50–150 km and lie about 50–110 km above the cloud deck.*[53] These altitudes are in the layer where weather occurs, the troposphere. Weather does not occur in the higher stratosphere or thermosphere. Unlike Uranus, Neptune's composition has a higher volume of ocean, whereas Uranus has a smaller mantle.*[54] Combined colour and near-infrared image of Neptune, show- ing bands of methane in its atmosphere, and four of its moons, Neptune's spectra suggest that its lower stratosphere , , , and . is hazy due to condensation of products of ultra- violet photolysis of methane, such as ethane and acetylene.*[11]*[16] The stratosphere is also home to that of Uranus, some unknown atmospheric constituent to trace amounts of and hydrogen is thought to contribute to Neptune's colour.*[14] cyanide.*[11]*[55] The stratosphere of Neptune is warmer than that of Uranus due to the elevated concen- Neptune's atmosphere is subdivided into two main re- tration of hydrocarbons.*[11] gions: the lower troposphere, where temperature de- creases with altitude, and the stratosphere, where tem- For reasons that remain obscure, the planet's thermo- perature increases with altitude. The boundary between sphere is at an anomalously high temperature of about the two, the tropopause, occurs at a pressure of 0.1 bars 750 K.*[56]*[57] The planet is too far from the Sun for (10 kPa).*[11] The stratosphere then gives way to the this heat to be generated by ultraviolet radiation. One thermosphere at a pressure lower than 10*−5 to 10*−4 candidate for a heating mechanism is atmospheric inter- microbars (1 to 10 Pa).*[11] The thermosphere gradually action with ions in the planet's magnetic field. Other transitions to the . candidates are gravity waves from the interior that dis- sipate in the atmosphere. The thermosphere contains traces of carbon dioxide and water, which may have been deposited from external sources such as meteorites and dust.*[52]*[55]

4.2.3 Magnetosphere

Neptune also resembles Uranus in its magnetosphere, with a magnetic field strongly tilted relative to its rotational axis at 47° and offset at least 0.55 radii, or about 13500 km from the planet's physical centre. Before Voyager 2's arrival at Neptune, it was hypothesised that Uranus's tilted magnetosphere was the result of its side- ways rotation. In comparing the magnetic fields of the two planets, scientists now think the extreme orientation may be characteristic of flows in the planets' interiors. This field may be generated by convective fluid motions Bands of high-altitude clouds cast shadows on Neptune's lower in a thin spherical shell of electrically conducting liquids cloud deck (probably a combination of ammonia, methane and wa- * * Models suggest that Neptune's troposphere is banded by ter) [52] resulting in a dynamo action. [58] clouds of varying compositions depending on altitude. The dipole component of the magnetic field at the mag- The upper-level clouds occur at pressures below one bar, netic equator of Neptune is about 14 microteslas (0.14 where the temperature is suitable for methane to con- G).*[59] The dipole magnetic moment of Neptune is 17 3 3 dense. For pressures between one and five bars (100 and about 2.2 × 10 T·m (14 μT·RN , where RN is the ra- 500 kPa), clouds of ammonia and hydrogen sulfide are dius of Neptune). Neptune's magnetic field has a complex believed to form. Above a pressure of five bars, the clouds that includes relatively large contributions from may consist of ammonia, ammonium sulfide, hydrogen non-dipolar components, including a strong quadrupole sulfide and water. Deeper clouds of water ice should be moment that may exceed the dipole moment in strength. 54 CHAPTER 4. NEPTUNE

By contrast, Earth, Jupiter and Saturn have only relatively ture,*[67] the cause of which is not understood but which small quadrupole moments, and their fields are less tilted may be due to the gravitational interaction with small from the polar axis. The large quadrupole moment of moons in orbit near them.*[68] Neptune may be the result of offset from the planet's cen- The outermost ring, Adams, contains five prominent arcs tre and geometrical constraints of the field's dynamo gen- * * now named Courage, Liberté, Egalité 1, Egalité 2 and Fra- erator. [60] [61] ternité (Courage, Liberty, Equality and Fraternity).*[69] Neptune's bow shock, where the magnetosphere begins The existence of arcs was difficult to explain because the to slow the solar wind, occurs at a distance of 34.9 times laws of motion would predict that arcs would spread out the radius of the planet. The magnetopause, where the into a uniform ring over short timescales. Astronomers pressure of the magnetosphere counterbalances the solar now believe that the arcs are corralled into their current wind, lies at a distance of 23–26.5 times the radius of form by the gravitational effects of Galatea, a moon just Neptune. The tail of the magnetosphere extends out to inward from the ring.*[70]*[71] at least 72 times the radius of Neptune, and likely much * Earth-based observations announced in 2005 appeared to farther. [60] show that Neptune's rings are much more unstable than previously thought. Images taken from the W. M. Keck Observatory in 2002 and 2003 show considerable decay 4.3 Planetary rings in the rings when compared to images by Voyager 2. In particular, it seems that the Liberté arc might disappear * Main article: in as little as one century. [72] Neptune has a planetary ring system, though one much 4.4 Climate

Neptune's rings, taken by Voyager 2 less substantial than that of Saturn. The rings may consist of ice particles coated with silicates or carbon-based ma- The Great Dark Spot (top), Scooter (middle white cloud),*[73] terial, which most likely gives them a reddish hue.*[62] and the (bottom), with contrast exaggerated. The three main rings are the narrow Adams Ring, 63,000 km from the centre of Neptune, the Le Verrier Ring, at Neptune's weather is characterised by extremely dynamic 53,000 km, and the broader, fainter Galle Ring, at 42,000 storm systems, with winds reaching speeds of almost km. A faint outward extension to the Le Verrier Ring has 600 m/s (2,200 km/h; 1,300 mph) —nearly reaching been named ; it is bounded at its outer edge by the * * supersonic flow. [15] More typically, by tracking the mo- Arago Ring at 57,000 km. [63] tion of persistent clouds, wind speeds have been shown to The first of these planetary rings was detected in 1968 vary from 20 m/s in the easterly direction to 325 m/s west- by a team led by Edward Guinan.*[18]*[64] In the early ward.*[74] At the cloud tops, the prevailing winds range 1980s, analysis of this data along with newer observa- in speed from 400 m/s along the equator to 250 m/s at tions led to the hypothesis that this ring might be incom- the poles.*[52] Most of the winds on Neptune move in a plete.*[65] Evidence that the rings might have gaps first direction opposite the planet's rotation.*[75] The general arose during a stellar occultation in 1984 when the rings pattern of winds showed prograde rotation at high lati- obscured a star on immersion but not on emersion.*[66] tudes vs. retrograde rotation at lower latitudes. The dif- Images by Voyager 2 in 1989 settled the issue by show- ference in flow direction is believed to be a“skin effect” ing several faint rings. These rings have a clumpy struc- and not due to any deeper atmospheric processes.*[11] At 4.4. CLIMATE 55

70° S latitude, a high-speed jet travels at a speed of 300 In 1989, the Great Dark Spot, an anti-cyclonic storm sys- m/s.*[11] tem spanning 13000×6600 km,*[76] was discovered by Neptune differs from Uranus in its typical level of me- NASA's Voyager 2 spacecraft. The storm resembled the teorological activity. Voyager 2 observed weather phe- Great Red Spot of Jupiter. Some five years later, on 2 nomena on Neptune during its 1989 fly-by,*[76] but no November 1994, the Hubble Space Telescope did not see comparable phenomena on Uranus during its 1986 fly-by. the Great Dark Spot on the planet. Instead, a new storm similar to the Great Dark Spot was found in the planet's The abundance of methane, ethane and ethyne at Nep- northern hemisphere.*[80] tune's equator is 10–100 times greater than at the poles. This is interpreted as evidence for upwelling at the equa- The Scooter is another storm, a white cloud group far- tor and subsidence near the poles.*[11] ther south than the Great Dark Spot. Its nickname came when it was first detected in the months before In 2007, it was discovered that the upper troposphere the 1989 Voyager 2 encounter it moved faster than the of Neptune's south pole was about 10 K warmer than Great Dark Spot.*[75] Subsequent images revealed even the rest of Neptune, which averages approximately 73 K faster clouds. The Small Dark Spot is a southern cyclonic (−200 °C). The temperature differential is enough to let storm, the second-most-intense storm observed during methane, which elsewhere is frozen in the troposphere, the 1989 encounter. It initially was completely dark, but escape into the stratosphere near the pole.*[77] The rela- as Voyager 2 approached the planet, a bright core devel- tive “hot spot”is due to Neptune's axial tilt, which has oped and can be seen in most of the highest-resolution exposed the south pole to the Sun for the last quarter of images.*[81] Neptune's year, or roughly 40 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the Neptune's dark spots are thought to occur in the south pole will be darkened and the north pole illumi- troposphere at lower altitudes than the brighter cloud fea- tures,*[82] so they appear as holes in the upper cloud nated, causing the methane release to shift to the north pole.*[78] decks. As they are stable features that can persist for sev- eral months, they are thought to be vortex structures.*[53] Because of seasonal changes, the cloud bands in the Often associated with dark spots are brighter, persis- southern hemisphere of Neptune have been observed to tent methane clouds that form around the tropopause increase in size and albedo. This trend was first seen in layer.*[83] The persistence of companion clouds shows 1980 and is expected to last until about 2020. The long that some former dark spots may continue to exist as cy- orbital period of Neptune results in seasons lasting forty clones even though they are no longer visible as a dark years.*[79] feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other un- known mechanism.*[84] 4.4.1 Storms 4.4.2 Internal heating

Neptune's more varied weather when compared to Uranus is believed to be due in part to its higher internal heating. Although Neptune lies half again as far from the Sun as Uranus, and receives only 40% its amount of sunlight,*[11] the two planets' surface temperatures are roughly equal.*[86] The upper regions of Neptune's troposphere reach a low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1 bar (100 kPa), the temperature is 72.00 K (−201.15 °C).*[87] Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from the Sun;*[88] whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun.*[89] Neptune is the farthest planet from the Sun, yet its internal energy is sufficient to drive the fastest planetary winds seen in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it is more difficult to simultaneously explain Uranus's lack of The Great Dark Spot, as imaged by Voyager 2 internal heat while preserving the apparent similarity be- 56 CHAPTER 4. NEPTUNE

barycentric orbit since its discovery in 1846,*[92]*[93] although it did not appear at its exact discovery position in the sky, because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July Neptune was also not at its exact discovery position in relation to the Sun; if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011.*[4]*[94]*[95] The elliptical orbit of Neptune is inclined 1.77° compared to that of Earth. The axial tilt of Neptune is 28.32°,*[96] which is similar to the tilts of Earth (23°) and Mars (25°). As a result, this planet experiences similar seasonal changes. The long or- bital period of Neptune means that the seasons last for forty Earth years.*[79] Its sidereal rotation period (day) is roughly 16.11 hours.*[4] Because its axial tilt is com- parable to Earth's, the variation in the length of its day over the course of its long year is not any more extreme. Four images taken a few hours apart with the NASA/ESA Hubble Because Neptune is not a solid body, its atmosphere un- Space Telescope's Wide Field Camera 3*[85] dergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field. tween the two planets.*[90] By contrast, the reverse is true for the polar regions where the rotation period is 12 hours. This differential rota- tion is the most pronounced of any planet in the So- 4.5 Orbit and rotation lar System,*[97] and it results in strong latitudinal wind shear.*[53]

4.5.1 Orbital resonances

Main articles: Kuiper belt, resonant trans-Neptunian ob- ject and Neptune's orbit has a profound impact on the region di-

Kuiper belt and orbital resonance

Pluto 1:2 2:3 Neptune 3:4 3:5 4:7 2:5

cubewanos twotinos

Neptune (red arc) completes one orbit around the Sun (center) for every 164.79 orbits of Earth. The light blue object represents Uranus.

The average distance between Neptune and the Sun is A diagram showing the major orbital resonances in the Kuiper 4.50 billion km (about 30.1 AU), and it completes an or- belt caused by Neptune: the highlighted regions are the 2:3 reso- “ ” bit on average every 164.79 years, subject to a variability nance (plutinos), the nonresonant classical belt (cubewanos), and the 1:2 resonance (twotinos). of around ±0.1 years. The perihelion distance is 29.81 * AU; the aphelion distance is 30.33 AU. [91] rectly beyond it, known as the Kuiper belt. The Kuiper On 11 July 2011, Neptune completed its first full belt is a ring of small icy worlds, similar to the asteroid 4.7. MOONS 57

belt but far larger, extending from Neptune's orbit at 30 suggest that the matter density in the outer regions of the AU out to about 55 AU from the Sun.*[98] Much in the Solar System was too low to account for the formation of same way that Jupiter's gravity dominates the asteroid such large bodies from the traditionally accepted method belt, shaping its structure, so Neptune's gravity dominates of core accretion, and various hypotheses have been ad- the Kuiper belt. Over the age of the Solar System, certain vanced to explain their creation. One is that the ice gi- regions of the Kuiper belt became destabilised by Nep- ants were not created by core accretion but from insta- tune's gravity, creating gaps in the Kuiper belt's structure. bilities within the original protoplanetary disc and later The region between 40 and 42 AU is an example.*[99] had their atmospheres blasted away by radiation from a nearby massive OB star.*[43] There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These An alternative concept is that they formed closer to the resonances occur when Neptune's orbital period is a pre- Sun, where the matter density was higher, and then sub- cise fraction of that of the object, such as 1:2, or 3:4. If, sequently migrated to their current orbits after the re- say, an object orbits the Sun once for every two Nep- moval of the gaseous protoplanetary disc.*[107] This tune orbits, it will only complete half an orbit by the hypothesis of migration after formation is favoured, time Neptune returns to its original position. The most due to its ability to better explain the occupancy of heavily populated resonance in the Kuiper belt, with over the populations of small objects observed in the trans- 200 known objects,*[100] is the 2:3 resonance. Objects Neptunian region.*[108] The current most widely ac- in this resonance complete 2 orbits for every 3 of Nep- cepted*[109]*[110]*[111] explanation of the details of tune, and are known as plutinos because the largest of the this hypothesis is known as the , which ex- known Kuiper belt objects, Pluto, is among them.*[101] plores the effect of a migrating Neptune and the other Although Pluto crosses Neptune's orbit regularly, the 2:3 giant planets on the structure of the Kuiper belt. resonance ensures they can never collide.*[102] The 3:4, 3:5, 4:7 and 2:5 resonances are less populated.*[103] Neptune has a number of known trojan objects occupying 4.7 Moons both the Sun–Neptune L4 and L5 Lagrangian points— gravitationally stable regions leading and trailing Neptune in its orbit, respectively.*[104] Neptune trojans can be Main article: viewed as being in a 1:1 resonance with Neptune. Some For a timeline of discovery dates, see Timeline of discov- Neptune trojans are remarkably stable in their orbits, and ery of Solar System planets and their moons. are likely to have formed alongside Neptune rather than Neptune has 14 known moons.*[6]*[112] Triton is the being captured. The first and so far only object identi- fied as associated with Neptune's trailing L5 Lagrangian point is 2008 LC18.*[105] Neptune also has a temporary quasi-satellite, (309239) 2007 RW10.*[106] The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for an- other 12,500 years. It is likely a captured object.*[106]

4.6 Formation and migration

Main articles: Formation and evolution of the Solar Sys- tem and Nice model The formation of the ice giants, Neptune and Uranus,

A simulation showing the outer planets and Kuiper belt: a) be- fore Jupiter and Saturn reached a 2:1 resonance; b) after inward scattering of Kuiper belt objects following the orbital shift of Nep- tune; c) after ejection of scattered Kuiper belt bodies by Jupiter Natural-colour view of Neptune with Proteus (top), Larissa (lower right) and Despina (left), from the Hubble Space Tele- has proven difficult to model precisely. Current models scope 58 CHAPTER 4. NEPTUNE largest Neptunian moon, comprising more than 99.5% of Neptune was the Roman god of the sea, Neptune's moons the mass in orbit around Neptune,*[lower-alpha 5] and it have been named after lesser sea gods.*[35] is the only one massive enough to be spheroidal. Triton was discovered by just 17 days after the discovery of Neptune itself. Unlike all other large plan- 4.8 Observation etary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming Neptune is never visible to the naked eye, having a bright- in place; it was probably once a dwarf planet in the Kuiper ness between magnitudes +7.7 and +8.0,*[6]*[9] which belt.*[113] It is close enough to Neptune to be locked can be outshone by Jupiter's Galilean moons, the dwarf into a synchronous rotation, and it is slowly spiralling in- planet and the asteroids 4 , , , ward because of . It will eventually be and 6 .*[120] A telescope or strong binocu- torn apart, in about 3.6 billion years, when it reaches the lars will resolve Neptune as a small blue disk, similar in .*[114] In 1989, Triton was the coldest object appearance to Uranus.*[121] that had yet been measured in the Solar System,*[115] with estimated temperatures of 38 K (−235 °C).*[116] Because of the distance of Neptune from Earth, the angular diameter of the planet only ranges from 2.2 to Neptune's second known satellite (by order of discovery), 2.4 arcseconds,*[6]*[9] the smallest of the Solar Sys- the , has one of the most eccentric tem planets. Its small apparent size has made it chal- orbits of any satellite in the Solar System. The eccentric- lenging to study visually. Most telescopic data was ity of 0.7512 gives it an apoapsis that is seven times its fairly limited until the advent of Hubble Space Tele- periapsis distance from Neptune.*[lower-alpha 6] scope and large ground-based telescopes with .*[122]*[123] From Earth, Neptune goes through apparent retrograde motion every 367 days, resulting in a looping motion against the background stars during each opposition. These loops carried it close to the 1846 discovery coor- dinates in April and July 2010 and again in October and November 2011.*[95] Observation of Neptune in the radio-frequency band shows that it is a source of both continuous emission and irregular bursts. Both sources are believed to originate from its rotating magnetic field.*[52] In the infrared part of the spectrum, Neptune's storms appear bright against the cooler background, allowing the size and shape of these features to be readily tracked.*[124]

4.9 Exploration

Neptune's moon Proteus Main article: Exploration of Neptune Voyager 2 is the only spacecraft that has visited Neptune. From July to September 1989, Voyager 2 discovered The spacecraft's closest approach to the planet occurred six new Neptunian moons.*[60] Of these, the irregu- on 25 August 1989. Because this was the last major planet larly shaped Proteus is notable for being as large as a the spacecraft could visit, it was decided to make a close body of its density can be without being pulled into a flyby of the moon Triton, regardless of the consequences spherical shape by its own gravity.*[117] Although the to the trajectory, similarly to what was done for Voyager second-most-massive Neptunian moon, it is only 0.25% 1's encounter with Saturn and its moon . The images relayed back to Earth from Voyager 2 became the basis of the mass of Triton. Neptune's innermost four moons * —, , Despina and Galatea —orbit close a 1989 PBS all-night program, Neptune All Night. [125] enough to be within Neptune's rings. The next-farthest During the encounter, signals from the spacecraft re- out, Larissa, was originally discovered in 1981 when it quired 246 minutes to reach Earth. Hence, for the most had occulted a star. This occultation had been attributed part, the Voyager 2 mission relied on preloaded com- to ring arcs, but when Voyager 2 observed Neptune in mands for the Neptune encounter. The spacecraft per- 1989, it was found to have caused it. Five new irreg- formed a near-encounter with the moon Nereid before it ular moons discovered between 2002 and 2003 were came within 4400 km of Neptune's atmosphere on 25 Au- announced in 2004.*[118]*[119] A and the gust, then passed close to the planet's largest moon Triton smallest yet, S/2004 N 1, was found in 2013. Because later the same day.*[126] 4.11. NOTES 59

4.11 Notes

[1] Orbital elements refer to the Neptune barycentre and Solar System barycentre. These are the instantaneous osculating values at the precise J2000 epoch. Barycentre quantities are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day basis from the motion of the moons.

[2] Refers to the level of 1 bar (100 kPa) atmospheric pressure

[3] Neptune is more dense and physically smaller than Uranus because Neptune's greater mass gravitationally com- presses the atmosphere more.

[4] The mass of Earth is 5.9736×1024 kg, giving a mass ratio of:

M × 26 Neptune = 1.02 10 = 17.09 MEarth 5.97×1024 The mass of Uranus is 8.6810×1025 kg, giving a mass ra- A Voyager 2 mosaic of Triton tio of:

M × 25 Uranus = 8.68 10 = 14.54 MEarth 5.97×1024 The spacecraft verified the existence of a magnetic field The mass of Jupiter is 1.8986×1027 kg, giving a mass ratio surrounding the planet and discovered that the field was of: offset from the centre and tilted in a manner similar to M × 27 Jupiter = 1.90 10 = 18.63 the field around Uranus. The question of the planet's ro- MNeptune 1.02×1026 tation period was settled using measurements of radio Mass values from Williams, David R. (29 November emissions. Voyager 2 also showed that Neptune had a 2007). “Planetary Fact Sheet – Metric”. NASA. Re- surprisingly active weather system. Six new moons were trieved 13 March 2008. discovered, and the planet was shown to have more than 22 one ring.*[60]*[126] [5] Mass of Triton: 2.14×10 kg. Combined mass of 12 other known moons of Neptune: 7.53×1019 kg, or 0.35%. In 2003, there was a proposal in NASA's “Vision The mass of the rings is negligible. Missions Studies”for a "Neptune Orbiter with Probes" ra = 2 −1=2/0.2488−1=7.039. mission that does Cassini-level science. The work is [6] rp 1−e being done in conjunction with JPL and the California Institute of Technology.*[127] Another, more recent proposal was for , a flyby spacecraft that would visit 4.12 References Jupiter, Saturn, Neptune, and a Kuiper belt object.*[128] However, the focus would be on Neptune and its largest [1] Hamilton, Calvin J. (4 August 2001).“Neptune”. Views moon Triton to help plug a predicted 50-year gap in of the Solar System. Retrieved 13 August 2007. exploration of the system.*[128]*[128] [2] Walter, Elizabeth (21 April 2003). Cambridge Advanced might have also done a flyby. Learner's Dictionary (2nd ed.). Cambridge University Press. ISBN 978-0-521-53106-1.

[3] Yeomans, Donald K. “HORIZONS Web-Interface for Neptune Barycenter (Major Body=8)". JPL Horizons On- 4.10 See also Line Ephemeris System. Retrieved 18 July 2014.—Se- lect“Ephemeris Type: Orbital Elements”,“Time Span: 2000-01-01 12:00 to 2000-01-02”.(“Target Body: Nep- • tune Barycenter”and“Center: Solar System Barycenter (@0)".) • Neptune in astrology [4] Munsell, K.; Smith, H.; Harvey, S. (13 November 2007). “Neptune: Facts & Figures”. NASA. Retrieved 14 Au- • Neptune in fiction gust 2007.

• Neptunium [5] Seligman, Courtney. “Rotation Period and Day Length” . Retrieved 13 August 2009.

• Neptune, the Mystic – one of the seven movements [6] Williams, David R. (1 September 2004). “Neptune Fact in Gustav Holst's Planets suite Sheet”. NASA. Retrieved 14 August 2007. 60 CHAPTER 4. NEPTUNE

[7] “The MeanPlane (Invariable plane) of the Solar System [21] Britt, Robert Roy (2009). “Galileo discovered Neptune, passing through the barycenter”. 3 April 2009. Retrieved new theory claims”. MSNBC News. Retrieved 10 July 10 April 2009. (produced with Solex 10 written by Aldo 2009. Vitagliano; see also Invariable plane) [22] Bouvard, A. (1821). Tables astronomiques publiées par le [8] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, de France. Paris: Bachelier. Michael F. et al. (2007). “Report of the IAU/IAG [23] Airy, G. B. (13 November 1846). “Account of Working Group on cartographic coordinates and some circumstances historically connected with rotational elements: 2006”. Celestial Mechan- the discovery of the planet exterior to Uranus”. ics and Dynamical Astronomy 98 (3): 155–180. Monthly Notices of the Royal Astronomical Soci- Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- ety 7: 121–144. Bibcode:1846MNRAS...7..121A. 007-9072-y. doi:10.1002/asna.18470251002.

[9] Espenak, Fred (20 July 2005). “Twelve Year Planetary [24] O'Connor, John J.; Robertson, Edmund F. (2006).“John Ephemeris: 1995–2006”. NASA. Retrieved 1 March Couch Adams' account of the discovery of Neptune”. 2008. University of St Andrews. Retrieved 18 February 2008.

[10] Chang, Kenneth (18 October 2014). “Dark Spots in Our [25] Adams, J. C. (13 November 1846). “Explanation of Knowledge of Neptune”. New York Times. Retrieved 21 the observed irregularities in the motion of Uranus, on October 2014. the hypothesis of disturbance by a more distant planet”. Monthly Notices of the Royal Astronomical Society 7: 149. [11] Lunine, Jonathan I. (September 1993). “The Bibcode:1846MNRAS...7..149A. Atmospheres of Uranus and Neptune”. An- nual Review of Astronomy and Astrophysics 31: [26] Challis, Rev. J. (13 November 1846). “Account 217–263. Bibcode:1993ARA&A..31..217L. of observations at the Cambridge observatory for de- doi:10.1146/annurev.aa.31.090193.001245. tecting the planet exterior to Uranus”. Monthly No- tices of the Royal Astronomical Society 7: 145–149. [12] Podolak, M.; Weizman, A.; Marley, M. (December Bibcode:1846MNRAS...7..145C. 1995). “Comparative models of Uranus and Neptune” . Planetary and Space Science 43 (12): 1517–1522. [27] Galle, J. G. (13 November 1846). “Account of Bibcode:1995P&SS...43.1517P. doi:10.1016/0032- the discovery of the planet of Le Verrier at Berlin”. 0633(95)00061-5. Monthly Notices of the Royal Astronomical Society 7: 153. Bibcode:1846MNRAS...7..153G. [13] Upper Surface of Neptune. Universetoday.com (9 De- [28] Kollerstrom, Nick (2001). “Neptune's Discovery. The cember 2008). Retrieved on 2013-07-28. British Case for Co-Prediction.”. University College Lon- don. Archived from the original on 11 November 2005. [14] Munsell, Kirk; Smith, Harman; Harvey, Samantha (13 Retrieved 19 March 2007. November 2007). “Neptune overview”. Solar System Exploration. NASA. Retrieved 20 February 2008. [29] William Sheehan; Nicholas Kollerstrom; Craig B. Waff (December 2004). “The Case of the Pilfered Planet – [15] Suomi, V. E.; Limaye, S. S.; Johnson, D. Did the British steal Neptune?". Scientific American. Re- R. (1991). “High Winds of Neptune: A trieved 20 January 2011. possible mechanism”. Science 251 (4996): 929–932. Bibcode:1991Sci...251..929S. [30] Moore (2000):206 doi:10.1126/science.251.4996.929. PMID 17847386. [31] Littmann, Mark (2004). Planets Beyond, Exploring the [16] Hubbard, W. B. (1997). “Neptune's Deep Outer Solar System. Courier Dover Publications. p. 50. Chemistry”. Science 275 (5304): 1279–1280. ISBN 978-0-486-43602-9. doi:10.1126/science.275.5304.1279. PMID 9064785. [32] Baum, Richard; Sheehan, William (2003). In Search of [17] Nettelmann, N.; French, M.; Holst, B.; Redmer, R. “In- Planet Vulcan: The Ghost in Newton's Clockwork Uni- terior Models of Jupiter, Saturn and Neptune” (PDF). verse. Basic Books. pp. 109–110. ISBN 978-0-7382- University of Rostock. Retrieved 25 February 2008. 0889-3. [33] Gingerich, Owen (1958). “The Naming of Uranus and [18] Wilford, John N. (10 June 1982). “Data Shows 2 Rings Neptune”. Astronomical Society of the Pacific Leaflets 8: Circling Neptune”. The New York Times. Retrieved 29 9–15. Bibcode:1958ASPL....8....9G. February 2008. [34] Hind, J. R. (1847). “Second report of proceedings in [19] Hirschfeld, Alan (2001). Parallax: The Race to Measure the Cambridge Observatory relating to the new Planet the Cosmos. New York, New York: Holt. ISBN (Neptune)". Astronomische Nachrichten 25 (21): 309. 978-0-8050-7133-7. doi:10.1002/asna.18470252102.

[20] Littmann, Mark; Standish, E. M. (2004). Planets Beyond: [35] Blue, Jennifer (17 December 2008).“Planet and Satellite Discovering the Outer Solar System. Courier Dover Publi- Names and Discoverers”. USGS. Retrieved 18 February cations. ISBN 978-0-486-43602-9. 2008. 4.12. REFERENCES 61

[36] “Planetary linguistics”. nineplanets.org. Retrieved 8 [52] Elkins-Tanton, Linda T. (2006). Uranus, Neptune, Pluto, April 2010. and the Outer Solar System. New York: Chelsea House. pp. 79–83. ISBN 978-0-8160-5197-7. [37] “Greek Names of the Planets”. Retrieved 14 July 2012. Neptune or Poseidon as is its Greek name, was the God of [53] Max, C. E.; Macintosh, B. A.; Gibbard, S. G.; Gavel, the Seas. It is the eight planet from the sun... See also the D. T. et al. (2003). “Cloud Structures on Nep- Greek article about the planet. tune Observed with Keck Telescope Adaptive Optics” . The Astronomical Journal, 125 (1): 364–375. [38] Long, Tony (21 January 2008).“Jan. 21, 1979: Neptune Bibcode:2003AJ....125..364M. doi:10.1086/344943. Moves Outside Pluto's Wacky Orbit”. Wired. Retrieved 13 March 2008. [54] Frances, Peter (2008). DK Universe. DK Publishing. pp. 196–201. ISBN 978-0-7566-3670-8. [39] Weissman, Paul R. (1995). “The Kuiper Belt” . Annual Review of Astronomy and Astrophysics [55] Encrenaz, Thérèse (February 2003). “ISO obser- 33: 327. Bibcode:1995ARA&A..33..327W. vations of the giant planets and Titan: what have we doi:10.1146/annurev.aa.33.090195.001551. learnt?". Planetary and Space Science 51 (2): 89–103. Bibcode:2003P&SS...51...89E. doi:10.1016/S0032- [40] “The Status of Pluto:A clarification”. International As- 0633(02)00145-9. tronomical Union, Press release. 1999. Archived from the original on 15 June 2006. Retrieved 25 May 2006. [56] Broadfoot, A.L.; Atreya, S.K.; Bertaux, J.L. et [41] “IAU 2006 General Assembly: Resolutions 5 and 6” al. (1999). “Ultraviolet Spectrometer Observa- (PDF). IAU. 24 August 2006. tions of Neptune and Triton” (PDF). Science 246 (4936): 1459–1456. Bibcode:1989Sci...246.1459B. [42] Unsöld, Albrecht; Baschek, Bodo (2001). The New Cos- doi:10.1126/science.246.4936.1459. PMID 17756000. mos: An Introduction to Astronomy and Astrophysics (5th ed.). Springer. p. 47. ISBN 978-3-540-67877-9. See [57] Herbert, Floyd; Sandel, Bill R. (August–September Table 3.1. 1999). “Ultraviolet observations of Uranus and Neptune”. Planetary and Space Science 47 (8– [43] , Alan P. (2002). “Formation of gas and ice 9): 1,119–1,139. Bibcode:1999P&SS...47.1119H. giant planets”. Earth and Planetary Science Letters doi:10.1016/S0032-0633(98)00142-1. 202 (3–4): 513–523. Bibcode:2002E&PSL.202..513B. doi:10.1016/S0012-821X(02)00808-7. [58] Stanley, Sabine; Bloxham, Jeremy (11 March 2004). “Convective-region geometry as the cause of Uranus' [44] Lovis, C.; Mayor, M.; Alibert Y.; Benz W. (18 May and Neptune's unusual magnetic fields”. Nature 2006). “Trio of Neptunes and their Belt”. ESO. Re- 428 (6979): 151–153. Bibcode:2004Natur.428..151S. trieved 25 February 2008. doi:10.1038/nature02376. PMID 15014493.

[45] Atreya, S.; Egeler, P.; Baines, K. (2006). “Water- [59] Connerney, J. E. P.; Acuña, Mario H.; Ness, ammonia ionic ocean on Uranus and Neptune?" (PDF). Norman F. (1991). “The magnetic field of Geophysical Research Abstracts 8: 05179. Neptune”. Journal of Geophysics Research 96: 19,023–42. Bibcode:1991JGR....9619023C. [46] Weird water lurking inside giant planets, New Scientist,1 doi:10.1029/91JA01165. September 2010, Magazine issue 2776. [60] Ness, N. F.; Acuña, M. H.; Burlaga, L. F.; Connerney, J. [47] Kerr, Richard A. (1999). “Neptune May Crush E. P. et al. (1989).“Magnetic Fields at Neptune”. Science Methane Into Diamonds”. Science 286 (5437): 25. 246 (4936): 1473–1478. Bibcode:1989Sci...246.1473N. doi:10.1126/science.286.5437.25a. PMID 10532884. doi:10.1126/science.246.4936.1473. PMID 17756002. [48] Bland, Eric (15 January 2010). “Diamond Oceans Pos- “ sible on Uranus, Neptune”. Discovery.com. Retrieved [61] , C. T.; Luhmann, J. G. (1997). Neptune: Mag- ” 17 May 2013. netic Field and Magnetosphere . University of California, Los Angeles. Retrieved 10 August 2006. [49] Baldwin, Emily (21 January 2010). “Oceans of diamond possible on Uranus and Neptune”. astronomynow.com. [62] Cruikshank, P. (1996). Neptune and Triton. Retrieved 6 February 2014. University of Arizona Press. pp. 703–804. ISBN 978- 0-8165-1525-7. [50] Podolak, M.; Weizman, A.; Marley, M. (1995). “Comparative models of Uranus and Neptune”. [63] Blue, Jennifer (8 December 2004). “Nomenclature Ring Planetary and Space Science 43 (12): 1517–1522. and Ring Gap Nomenclature”. Gazetteer of Planetary. Bibcode:1995P&SS...43.1517P. doi:10.1016/0032- USGS. Retrieved 28 February 2008. 0633(95)00061-5. [64] Guinan, E. F.; Harris, C. C.; Maloney, F. P. (1982). [51] Crisp, D.; Hammel, H. B. (14 June 1995).“Hubble Space “Evidence for a Ring System of Neptune”. Bul- Telescope Observations of Neptune”. Hubble News Cen- letin of the American Astronomical Society 14: 658. ter. Retrieved 22 April 2007. Bibcode:1982BAAS...14..658G. 62 CHAPTER 4. NEPTUNE

[65] Goldreich, P.; Tremaine, S.; Borderies, N. E. F. (1986). [81] Lavoie, Sue (29 January 1996). “PIA00064: Neptune's “Towards a theory for Neptune's arc rings”. Astronom- Dark Spot (D2) at High Resolution”. NASA JPL. Re- ical Journal 92: 490–494. Bibcode:1986AJ.....92..490G. trieved 28 February 2008. doi:10.1086/114178. [82] S. G., Gibbard; de Pater, I.; Roe, H. G.; Martin, S. et al. [66] Nicholson, P. D. et al. (1990). “Five Stellar Oc- (2003). “The altitude of Neptune cloud features from cultations by Neptune: Further Observations of Ring high-spatial-resolution near-infrared spectra” (PDF). Arcs”. Icarus 87 (1): 1. Bibcode:1990Icar...87....1N. Icarus 166 (2): 359–374. Bibcode:2003Icar..166..359G. doi:10.1016/0019-1035(90)90020-A. doi:10.1016/j.icarus.2003.07.006. Retrieved 26 Febru- ary 2008. [67] “Missions to Neptune”. The Planetary Society. 2007. Archived from the original on 11 February 2010. Re- [83] Stratman, P. W.; Showman, A. P.; Dowling, T. E.; Sro- trieved 11 October 2007. movsky, L. A. (2001). “EPIC Simulations of Bright Companions to Neptune's Great Dark Spots” (PDF). [68] Wilford, John Noble (15 December 1989). “Scientists Icarus 151 (2): 275–285. Bibcode:1998Icar..132..239L. Puzzled by Unusual Neptune Rings”. Hubble News Desk. doi:10.1006/icar.1998.5918. Retrieved 26 February Retrieved 29 February 2008. 2008. [69] Cox, Arthur N. (2001). Allen's Astrophysical Quantities. [84] Sromovsky, L. A.; Fry, P. M.; Dowling, T. E.; Baines, K. Springer. ISBN 0-387-98746-0. H. (2000). “The unusual dynamics of new dark spots on ” [70] Munsell, Kirk; Smith, Harman; Harvey, Samantha (13 Neptune . Bulletin of the American Astronomical Society November 2007). “Planets: Neptune: Rings”. Solar 32: 1005. Bibcode:2000DPS....32.0903S. System Exploration. NASA. Retrieved 29 February 2008. [85] “Happy birthday Neptune”. ESA/Hubble. Retrieved 13 [71] Salo, Heikki; Hänninen, Jyrki (1998). “Nep- July 2011. tune's Partial Rings: Action of Galatea on [86] Williams, Sam (24 November 2004). “Heat Sources Self-Gravitating Arc Particles”. Science 282 Within the Giant Planets” (DOC). UC Berkeley. Re- (5391): 1102–1104. Bibcode:1998Sci...282.1102S. trieved 20 February 2008. doi:10.1126/science.282.5391.1102. PMID 9804544. [87] Lindal, Gunnar F. (1992). “The atmosphere of Nep- [72] “Neptune's rings are fading away”. New Scientist. 26 tune – an analysis of radio occultation data acquired March 2005. Retrieved 6 August 2007. with Voyager 2”. Astronomical Journal 103: 967–982. Bibcode:1992AJ....103..967L. doi:10.1086/116119. [73] Lavoie, Sue (8 January 1998). “PIA01142: Neptune Scooter”. NASA. Retrieved 26 March 2006. [88] “Class 12 – Giant Planets – Heat and Formation”. 3750 – Planets, Moons & Rings. Colorado University, Boulder. [74] Hammel, H. B.; Beebe, R. F.; De Jong, E. M.; Hansen, 2004. Retrieved 13 March 2008. C. J. et al. (1989). “Neptune's wind speeds ob- tained by tracking clouds in Voyager 2 images”. Science [89] Pearl, J. C.; Conrath, B. J. (1991). “The albedo, 245 (4924): 1367–1369. Bibcode:1989Sci...245.1367H. effective temperature, and energy balance of Nep- doi:10.1126/science.245.4924.1367. PMID 17798743. tune, as determined from Voyager data”. Journal of Geophysical Research Supplement 96: 18,921–18,930. [75] Burgess (1991):64–70. Bibcode:1991JGR....9618921P. doi:10.1029/91ja01087. [76] Lavoie, Sue (16 February 2000). “PIA02245: Nep- [90] Imke de Pater and Jack J. Lissauer (2001), Planetary Sci- tune's blue-green atmosphere”. NASA JPL. Retrieved ences, 1st edition, page 224. 28 February 2008. [91] Jean Meeus, Astronomical Algorithms (Richmond, VA: [77] Orton, G. S.; Encrenaz T.; Leyrat C.; Puetter, R. Willmann-Bell, 1998) 273. Supplemented by further use et al. (2007). “Evidence for methane escape and of VSOP87. The last three aphelia were 30.33 AU, the strong seasonal and dynamical perturbations of Nep- next is 30.34 AU. The perihelia are even more stable at tune's atmospheric temperatures”. Astronomy and As- 29.81 AU trophysics 473: L5–L8. Bibcode:2007A&A...473L...5O. doi:10.1051/0004-6361:20078277. [92] McKie, Robin (9 July 2011). “Neptune's first orbit: a turning point in astronomy”. The Guardian. [78] Orton, Glenn; Encrenaz, Thérèse (18 September 2007). “A Warm South Pole? Yes, On Neptune!". ESO. Re- [93] “Neptune Completes First Orbit Since Discovery: 11th trieved 20 September 2007. July 2011 (at 21:48 U.T.±15min)". 1 July 2011. Re- trieved 10 July 2011. [79] Villard, Ray; Devitt, Terry (15 May 2003). “Brighter Neptune Suggests A Planetary Change Of Seasons”. [94] Nancy Atkinson (26 August 2010). “Clearing the Con- Hubble News Center. Retrieved 26 February 2008. fusion on Neptune’s Orbit”. Universe Today. Retrieved 10 July 2011. (Bill Folkner at JPL) [80] Hammel, H. B.; Lockwood, G. W.; Mills, J. R.; Bar- net, C. D. (1995). “Hubble Space Telescope Imag- [95] Anonymous (16 November 2007). “Horizons Output ing of Neptune's Cloud Structure in 1994”. Science for Neptune 2010–2011”. Retrieved 25 February 2008. 268 (5218): 1740–1742. Bibcode:1995Sci...268.1740H. —Numbers generated using the Solar System Dynamics doi:10.1126/science.268.5218.1740. PMID 17834994. Group, Horizons On-Line Ephemeris System. 4.12. REFERENCES 63

[96] Williams, David R. (6 January 2005). “Planetary Fact [109] Crida, A. (2009). “Solar System formation” Sheets”. NASA. Retrieved 28 February 2008. . Reviews in Modern Astronomy 21: 3008. arXiv:0903.3008. Bibcode:2009arXiv0903.3008C. [97] Hubbard, W. B.; Nellis, W. J.; Mitchell, A. C.; doi:10.1002/9783527629190.ch12. , N. C. et al. (1991). “Interior Struc- ture of Neptune: Comparison with Uranus”. Science [110] Desch, S. J. (2007). “Mass Distribution and Planet For- 253 (5020): 648–651. Bibcode:1991Sci...253..648H. mation in the Solar Nebula”. The Astrophysical Jour- doi:10.1126/science.253.5020.648. PMID 17772369. nal 671 (1): 878–893. Bibcode:2007ApJ...671..878D. doi:10.1086/522825. [98] Stern, S. Alan; Colwell, Joshua E. (1997). “Colli- sional Erosion in the Primordial Edgeworth-Kuiper Belt [111] Smith, R.; L. J. Churcher; M. C. Wyatt; M. M. Moerchen and the Generation of the 30–50 AU Kuiper Gap” et al. (2009). “Resolved debris disc emission around η . The Astrophysical Journal (Geophysical, Astrophys- Telescopii: a young solar system or ongoing planet for- ical, and Planetary Sciences, Space Science Depart- mation?". Astronomy and Astrophysics 493 (1): 299– ment, Southwest Research Institute) 490 (2): 879–882. 308. arXiv:0810.5087. Bibcode:2009A&A...493..299S. Bibcode:1997ApJ...490..879S. doi:10.1086/304912. doi:10.1051/0004-6361:200810706.

[99] Petit, Jean-Marc; Morbidelli, Alessandro; Valsecchi, [112] Hubble Space Telescope discovers fourteenth tiny moon Giovanni B. (1999). “Large Scattered orbiting Neptune | Space, Military and Medicine. and the Excitation of the Small Body Belts” (PDF). News.com.au (16 July 2013). Retrieved on 2013-07-28. Icarus 141 (2): 367. Bibcode:1999Icar..141..367P. doi:10.1006/icar.1999.6166. Retrieved 23 June 2007. [113] Agnor, Craig B.; Hamilton, Douglas P. (2006). “Nep- tune's capture of its moon Triton in a binary–planet grav- [100] “List Of Transneptunian Objects”. . itational encounter”. Nature (Nature Publishing Group) Retrieved 25 October 2010. 441 (7090): 192–194. Bibcode:2006Natur.441..192A. doi:10.1038/nature04792. PMID 16688170. [101] Jewitt, David (2004).“The Plutinos”. UCLA. Retrieved 28 February 2008. [114] Chyba, Christopher F.; Jankowski, D. G.; Nicholson, P. D. (1989). “Tidal evolution in the Neptune-Triton sys- [102] Varadi, F. (1999). “Periodic Orbits in the 3:2 Orbital tem”. Astronomy and Astrophysics (EDP Sciences) 219 Resonance and Their Stability”. The Astronomical Jour- (1–2): L23–L26. Bibcode:1989A&A...219L..23C. nal 118 (5): 2526–2531. Bibcode:1999AJ....118.2526V. doi:10.1086/301088. [115] Wilford, John N. (29 August 1989). “Triton May Be Coldest Spot in Solar System”. The New York Times. [103] John Davies (2001). Beyond Pluto: Exploring the outer Retrieved 29 February 2008. limits of the solar system. Cambridge University Press. p. 104. ISBN 0-521-80019-6. [116] Nelson, R. M.; Smythe, W. D.; Wallis, B. D.; Horn, L. J. et al. (1990). “Temperature and Thermal Emissivity [104] Chiang, E. I.; Jordan, A. B.; Millis, R. L.; M. W. Buie of the Surface of Neptune's Satellite Triton”. Science et al. (2003). “Resonance Occupation in the Kuiper 250 (4979): 429–431. Bibcode:1990Sci...250..429N. Belt: Case Examples of the 5 : 2 and Trojan Res- doi:10.1126/science.250.4979.429. PMID 17793020. onances”. The Astronomical Journal 126: 430–443. arXiv:astro-ph/0301458. Bibcode:2003AJ....126..430C. [117] Brown, Michael E.. “The Dwarf Planets”. California doi:10.1086/375207. Institute of Technology, Department of Geological Sci- ences. Retrieved 9 February 2008. [105] Sheppard, Scott S.; Trujillo, A. (10 September 2010). “Detection of a Trail- [118] Holman, M. J.; Kavelaars, J. J.; Grav, T. ing (L5) Neptune Trojan”. Science 329 et al. (2004). “Discovery of five irregu- (5997): 1304. Bibcode:2010Sci...329.1304S. lar moons of Neptune” (PDF). Nature 430 doi:10.1126/science.1189666. PMID 20705814. (7002): 865–867. Bibcode:2004Natur.430..865H. doi:10.1038/nature02832. PMID 15318214. Retrieved [106] De La Fuente Marcos, C. & De La Fuente Mar- 2011-10-24. cos, R. (2012). "(309239) 2007 RW10: a large temporary quasi-satellite of Neptune”. Astronomy [119] “Five new moons for planet Neptune”. BBC News. 18 and Astrophysics Letters 545: L9. arXiv:1209.1577. August 2004. Retrieved 6 August 2007. Bibcode:2012A&A...545L...9D. doi:10.1051/0004- 6361/201219931. [120] See the respective articles for magnitude data.

[107] Thommes, Edward W.; Duncan, Martin J.; Levison, [121] Moore (2000):207. Harold F. (2001). “The formation of Uranus and Nep- tune among Jupiter and Saturn”. The Astronomical [122] In 1977, for example, even the rotation period of Neptune Journal 123 (5): 2862–2883. arXiv:astro-ph/0111290. remained uncertain. Cruikshank, D. P. (1 March 1978). Bibcode:2002AJ....123.2862T. doi:10.1086/339975. “On the rotation period of Neptune”. Astrophysical Jour- nal, Part 2 – Letters to the Editor (University of Chicago [108] Hansen, Kathryn (7 June 2005).“Orbital shuffle for early Press) 220: L57–L59. Bibcode:1978ApJ...220L..57C. solar system”. Geotimes. Retrieved 26 August 2007. doi:10.1086/182636. 64 CHAPTER 4. NEPTUNE

[123] Max, C.; MacIntosh, B.; Gibbard, S.; Roe, H. et al. (1999). “Adaptive Optics Imaging of Neptune and Titan with the W.M. Keck Telescope”. Bul- letin of the American Astronomical Society 31: 1512. Bibcode:1999BAAS...31.1512M. [124] Gibbard, S. G.; Roe, H.; de Pater, I.; Macin- tosh, B. et al. (1999). “High-Resolution In- frared Imaging of Neptune from the Keck Telescope” . Icarus 156 (1): 1–15. Bibcode:2002Icar..156....1G. doi:10.1006/icar.2001.6766. [125] Phillips, Cynthia (5 August 2003).“Fascination with Dis- tant Worlds”. SETI Institute. Archived from the original on 3 November 2007. Retrieved 3 October 2007. [126] Burgess (1991):46–55. [127] Spilker, T. R.; Ingersoll, A. P. (2004).“Outstanding Sci- ence in the Neptune System From an Aerocaptured Vision Mission”. Bulletin of the American Astronomical Society 36: 1094. Bibcode:2004DPS....36.1412S. [128] Argo - A Voyage Through the Outer Solar System

4.13 Bibliography

• Burgess, Eric (1991). Far Encounter: The Neptune System. Columbia University Press. ISBN 978-0- 231-07412-4. • Moore, Patrick (2000). The Data Book of Astron- omy. CRC Press. ISBN 978-0-7503-0620-1.

4.14 Further reading

• Miner, Ellis D.; Wessen, Randii R. (2002). Neptune: The Planet, Rings, and Satellites. Springer-Verlag. ISBN 978-1-85233-216-7. • Standage, Tom (2001). The Neptune File. Penguin. ISBN 978-0-8027-1363-6.

4.15 External links

• NASA's Neptune fact sheet • Neptune from Bill Arnett's nineplanets.org • Neptune Astronomy Cast episode No. 63, includes full transcript. • Neptune Profile at NASA's Solar System Explo- ration site • Planets – Neptune A children's guide to Neptune. • Merrifield, Michael; Bauer, Amanda (2010). “Neptune”. Sixty Symbols. Brady Haran for the University of Nottingham. • Neptune by amateur (The Planetary Society) Chapter 5

Saturn

This article is about the planet. For other uses, see Saturn (disambiguation).

Saturn is the sixth planet from the Sun and the sec- ond largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth.*[10]*[11] Although only one-eighth the average density of Earth, with its larger volume Saturn is just over 95 times more massive.*[12]*[13]*[14] Saturn is named after the Roman god of agriculture, its astronomical sym- bol (♄) represents the god's sickle. Saturn's interior is probably composed of a core con- sisting of iron–nickel and rock (silicon and oxygen com- pounds), surrounded by a deep layer of metallic hydro- gen, an intermediate layer of liquid hydrogen and liquid * helium and a gaseous outer layer. [15] Saturn has a pale Composite image roughly comparing the sizes of Saturn and yellow hue due to ammonia crystals in its upper atmo- Earth sphere. Electrical current within the metallic hydro- gen layer is thought to give rise to Saturn's planetary magnetic field, which is weaker than Earth's, but has a surface, though it may have a solid core.*[20] Saturn's magnetic moment 580 times that of Earth due to Saturn's rotation causes it to have the shape of an oblate spheroid; larger size. Saturn's magnetic field strength is around that is, it is flattened at the poles and bulges at its equa- one-twentieth the strength of Jupiter's.*[16] The outer tor. Its equatorial and polar radii differ by almost 10%: atmosphere is generally bland and lacking in contrast, al- 60,268 km versus 54,364 km, respectively.*[4] Jupiter, though long-lived features can appear. Wind speeds on Uranus, and Neptune, the other giant planets in the Solar Saturn can reach 1,800 km/h (500 m/s), faster than on System, are also oblate but to a lesser extent. Saturn is Jupiter, but not as fast as those on Neptune.*[17] the only planet of the Solar System that is less dense than water—about 30% less.*[21] Although Saturn's core is Saturn has a prominent ring system that consists of nine considerably denser than water, the average specific den- continuous main rings and three discontinuous arcs and sity of the planet is 0.69 g/cm3 due to the gaseous at- that is composed mostly of ice particles with a smaller mosphere. Jupiter has 318 times the Earth's mass,*[22] amount of rocky debris and dust. Sixty-two*[18] moons while Saturn is 95 times the mass of the Earth,*[4] To- are known to orbit Saturn, of which fifty-three are of- gether, Jupiter and Saturn hold 92% of the total planetary ficially named. This does not include the hundreds of mass in the Solar System.*[23] moonlets comprising the rings. Titan, Saturn's largest and the Solar System's second largest moon, is larger than the On 8 January 2015, NASA reported determining the cen- planet Mercury and is the only moon in the Solar System ter of the planet Saturn and its family of moons to within to have a substantial atmosphere.*[19] 4 km (2.5 mi).*[24]

5.1.1 Internal structure 5.1 Physical characteristics Despite consisting mostly of hydrogen and helium, most Saturn is a gas giant because it is predominantly com- of Saturn's mass is not in the gas phase, because hydrogen posed of hydrogen and helium ('gas'). It lacks a definite becomes a non-ideal liquid when the density is above 0.01

65 66 CHAPTER 5. SATURN g/cm3, which is reached at a radius containing 99.9% to the abundance of this element in the Sun.*[25] The of Saturn's mass. The temperature, pressure, and den- quantity of elements heavier than helium is not known sity inside Saturn all rise steadily toward the core, which, precisely, but the proportions are assumed to match the in the deeper layers, cause hydrogen to transition into a primordial abundances from the formation of the Solar metal.*[23] System. The total mass of these heavier elements is es- timated to be 19–31 times the mass of the Earth, with a Standard planetary models suggest that the interior of Sat- * urn is similar to that of Jupiter, having a small rocky significant fraction located in Saturn's core region. [36] core surrounded by hydrogen and helium with trace Trace amounts of ammonia, acetylene, ethane, , amounts of various volatiles.*[25] This core is similar phosphine and methane have been detected in Sat- in composition to the Earth, but more dense. Exami- urn's atmosphere.*[37]*[38]*[39] The upper clouds are nation of Saturn's gravitational moment, in combination composed of ammonia crystals, while the lower level with physical models of the interior, allowed French as- clouds appear to consist of either ammonium hydrosul- * tronomers Didier Saumon and Tristan Guillot to place fide (NH4SH) or water. [40] Ultraviolet radiation from constraints on the mass of Saturn's core. In 2004, they the Sun causes methane photolysis in the upper atmo- estimated that the core must be 9–22 times the mass of sphere, leading to a series of hydrocarbon chemical re- the Earth,*[26]*[27] which corresponds to a diameter of actions with the resulting products being carried down- about 25,000 km.*[28] This is surrounded by a thicker ward by eddies and diffusion. This photochemical cycle liquid metallic hydrogen layer, followed by a liquid layer is modulated by Saturn's annual seasonal cycle.*[39] of helium-saturated molecular hydrogen that gradually transitions into gas with increasing altitude. The outer- most layer spans 1,000 km and consists of a gaseous at- 5.2.1 Cloud layers mosphere.*[29]*[30]*[31] Saturn has a hot interior, reaching 11,700 °C at its core, and it radiates 2.5 times more energy into space than it receives from the Sun. Most of this extra energy is gen- erated by the Kelvin–Helmholtz mechanism of slow grav- itational compression, but this alone may not be suffi- cient to explain Saturn's heat production. An additional mechanism may be generation of heat through the“rain- ing out”of droplets of helium deep in Saturn's interior. As the droplets descend through the lower-density hydro- gen, the process releases heat by friction and leaves Sat- urn's outer layers depleted of helium.*[32]*[33] These descending droplets may have accumulated into a helium shell surrounding the core.*[25]

5.2 Atmosphere

A global storm girdles the planet in 2011. The head of the storm (bright area) passes the tail circling around the left limb.

Saturn's atmosphere exhibits a banded pattern similar to Jupiter's, but Saturn's bands are much fainter and are much wider near the equator. The nomenclature used to describe these bands is the same as on Jupiter. Saturn's finer cloud patterns were not observed until the flybys of the Voyager spacecraft during the 1980s. Since then, Earth-based telescopy has improved to the point where regular observations can be made.*[41] The composition of the clouds varies with depth and in- Auroral lights at Saturn’s north pole.*[34] creasing pressure. In the upper cloud layers, with the tem- perature in the range 100–160 K and pressures extending The outer atmosphere of Saturn contains 96.3% molec- between 0.5–2 bar, the clouds consist of ammonia ice. ular hydrogen and 3.25% helium by volume.*[35] The Water ice clouds begin at a level where the pressure is proportion of helium is significantly deficient compared about 2.5 bar and extend down to 9.5 bar, where temper- 5.2. ATMOSPHERE 67

atures range from 185–270 K. Intermixed in this layer is a band of ammonium hydrosulfide ice, lying in the pressure A persisting hexagonal wave pattern around the north po- range 3–6 bar with temperatures of 290–235 K. Finally, lar vortex in the atmosphere at about 78°N was first noted the lower layers, where pressures are between 10–20 bar in the Voyager images.*[48]*[49]*[50] and temperatures are 270–330 K, contains a region of water droplets with ammonia in aqueous solution.*[42] The sides of the hexagon are each about 13,800 km (8,600 mi) long, which is longer than the diameter of the Saturn's usually bland atmosphere occasionally exhibits Earth.*[51] The entire structure rotates with a period of long-lived ovals and other features common on Jupiter. 10h 39m 24s (the same period as that of the planet's ra- In 1990, the Hubble Space Telescope imaged an enor- dio emissions) which is assumed to be equal to the period mous white cloud near Saturn's equator that was not of rotation of Saturn's interior.*[52] The hexagonal fea- present during the Voyager encounters and in 1994, an- ture does not shift in longitude like the other clouds in the other, smaller storm was observed. The 1990 storm visible atmosphere.*[53] was an example of a , a unique but short-lived phenomenon that occurs once every Satur- The pattern's origin is a matter of much speculation. Most nian year, roughly every 30 Earth years, around the time astronomers believe it was caused by some standing-wave of the northern hemisphere's summer .*[43] Pre- pattern in the atmosphere. Polygonal shapes have been vious Great White Spots were observed in 1876, 1903, replicated in the laboratory through differential rotation 1933 and 1960, with the 1933 storm being the most fa- of fluids.*[54]*[55] mous. If the periodicity is maintained, another storm will occur in about 2020.*[44] The winds on Saturn are the second fastest among the So- 5.2.3 South pole vortex lar System's planets, after Neptune's. Voyager data indi- cate peak easterly winds of 500 m/s (1800 km/h).*[45] In images from the Cassini spacecraft during 2007, Saturn's northern hemisphere displayed a bright blue hue, similar to Uranus. The color was most likely caused by Rayleigh scattering.*[46] Infrared imaging has shown that Saturn's south pole has a warm polar vortex, the only known ex- ample of such a phenomenon in the Solar System.*[47] Whereas temperatures on Saturn are normally −185 °C, temperatures on the vortex often reach as high as −122 °C, believed to be the warmest spot on Saturn.*[47]

5.2.2 North pole hexagonal cloud pattern

Saturn's south pole storm

HST imaging of the south polar region indicates the pres- ence of a , but no strong polar vortex nor any hexagonal standing wave.*[56] NASA reported in November 2006 that Cassini had observed a "hurricane- like”storm locked to the south pole that had a clearly defined eyewall.*[57]*[58] Eyewall clouds had not previ- ously been seen on any planet other than Earth. For ex- ample, images from the Galileo spacecraft did not show an eyewall in the Great Red Spot of Jupiter.*[59] Saturn – North polar hexagon and vortex as well as rings (2 April 2014) The south pole storm may have been present for billions of years.*[60] This vortex is comparable to the size of Main article: Saturn's hexagon Earth, and it has winds of 550 km/h.*[60] 68 CHAPTER 5. SATURN

5.2.4 Other features 5.4 Orbit and rotation

Cassini has observed a series of cloud features nicknamed “String of Pearls”found in northern latitudes. These fea- tures are cloud clearings that reside in deeper cloud lay- ers.*[61]

5.3 Magnetosphere

Main article: The average distance between Saturn and the Sun is over Saturn has an intrinsic magnetic field that has a sim- 1.4 billion kilometres (9 AU). With an average of 9.69 km/s,*[4] it takes Saturn 10,759 Earth 1 * days (or about 29 ⁄2 years), [66] to finish one revolution around the Sun.*[4] The elliptical orbit of Saturn is in- clined 2.48° relative to the orbital plane of the Earth.*[4] The perihelion and aphelion distances are, respectively, 9.022 and 10.053 au, on average.*[67] The visible fea- tures on Saturn rotate at different rates depending on lat- itude and multiple rotation periods have been assigned to various regions (as in Jupiter's case). System I has a period of 10 h 14 min 00 s (844.3°/d) and encompasses the Equatorial Zone, the South Equatorial Belt and the North Equatorial Belt. All other Saturnian latitudes, excluding the north and south polar regions, are indicated as System II and have been assigned a rotation period of 10 h 38 min 25.4 s (810.76°/d). The polar regions are considered to have rotation rates similar to System I. System III refers to Saturn's internal rotation rate. Based HST UV image of Saturn taken near showing both polar on radio emissions from the planet in the period of the aurorae Voyager flybys, it has been assigned a rotation period of 10 h 39 min 22.4 s (810.8°/d). Because it is close * ple, symmetric shape – a magnetic dipole. Its strength to System II, it has largely superseded it. [68] A precise at the equator – 0.2 gauss (20 µT) – is approximately one value for the rotation period of the interior remains elu- twentieth of that of the field around Jupiter and slightly sive. While approaching Saturn in 2004, Cassini found weaker than Earth's magnetic field.*[16] As a result Sat- that the radio rotation period of Saturn had increased * appreciably, to approximately 10 h 45 m 45 s (± 36 urn's magnetosphere is much smaller than Jupiter's. [62] * * When Voyager 2 entered the magnetosphere, the solar s). [69] [70] In March 2007, it was found that the vari- wind pressure was high and the magnetosphere ex- ation of radio emissions from the planet did not match tended only 19 Saturn radii, or 1.1 million km (712,000 Saturn's rotation rate. This variance may be caused by mi),*[63] although it enlarged within several hours, and geyser activity on Saturn's moon . The water remained so for about three days.*[64] Most probably, vapor emitted into Saturn's orbit by this activity becomes the magnetic field is generated similarly to that of Jupiter charged and creates a drag upon Saturn's magnetic field, slowing its rotation slightly relative to the rotation of the – by currents in the liquid metallic-hydrogen layer called * * * a metallic-hydrogen dynamo.*[62] This magnetosphere is planet. [71] [72] [72] efficient at deflecting the solar wind particles from the The latest estimate of Saturn's rotation (as an indicated Sun. The moon Titan orbits within the outer part of rotation rate for Saturn as a whole) based on a compila- Saturn's magnetosphere and contributes plasma from the tion of various measurements from the Cassini, Voyager ionized particles in Titan's outer atmosphere.*[16] Sat- and Pioneer probes was reported in September 2007 is 10 urn's magnetosphere, like Earth's, produces aurorae.*[65] hours, 32 minutes, 35 seconds.*[73] 5.6. NATURAL SATELLITES 69

5.5 Planetary rings Atlas cause weak, linear density waves in Saturn's rings that have yielded more reliable calculations of their masses.*[81] Main article:

5.6 Natural satellites

Main article: Saturn has at least 150 moons and moonlets, 53 of which

The rings of Saturn (imaged here by Cassini in 2007) are the most massive and conspicuous in the Solar System.*[30]

A montage of Saturn and its principal moons (, , False-color UV image of Saturn's outer B and A rings; , Enceladus, and Titan; not shown). This dirtier ringlets in the Cassini Division and Enke Gap famous image was created from photographs taken in November show up red. 1980 by the Voyager 1 spacecraft.

Saturn is probably best known for the system of planetary have formal names.*[82]*[83] Titan, the largest, com- rings that makes it visually unique.*[30] The rings extend prises more than 90% of the mass in orbit around Saturn, from 6,630 km to 120,700 km above Saturn's equator, av- including the rings.*[84] Saturn's second largest moon, erage approximately 20 meters in thickness and are com- Rhea, may have a tenuous ring system of its own,*[85] posed of 93% water ice with traces of impurities along with a tenuous atmosphere.*[86]*[87]*[88]*[89] and 7% amorphous carbon.*[74] The particles that make up the rings range in size from specks of dust up to 10 m.*[75] While the other gas giants also have ring systems, Saturn's is the largest and most visible. There are two main hypotheses regarding the origin of the rings. One hypothesis is that the rings are remnants of a destroyed moon of Saturn. The second hypothesis is that the rings are left over from the original nebular material from which Saturn formed. Some ice in the central rings comes from the moon Enceladus's ice volcanoes.*[76] In the past, astronomers believed the rings formed alongside the planet when it formed billions of years ago.*[77] In- stead, the age of these planetary rings is probably some hundreds of millions of years.*[78] Beyond the main rings at a distance of 12 million km from the planet is the sparse ring, which is tilted at an angle of 27° to the other rings and, like Phoebe, orbits in retrograde fashion.*[79] Some of the moons of Saturn, including and Possible beginning of a new moon of Saturn (15 April 2013). , act as shepherd moons to confine the rings and prevent them from spreading out.*[80] and Many of the other moons are small: 34 are less than 70 CHAPTER 5. SATURN

10 km in diameter and another 14 less than 50 km but suit. (In modern Greek, the planet retains its ancient larger than 10 km.*[90] Traditionally, most of Saturn's name Cronus—Κρόνος: Kronos.)*[109] moons have been named after Titans of Greek mythol- The Greek scientist Ptolemy based his calculations of Sat- ogy. Titan is the only satellite in the Solar System with a * * urn's orbit on observations he made while the planet was major atmosphere [91] [92] in which a complex organic in opposition.*[110] In , there are nine as- chemistry occurs. It is the only satellite with hydrocarbon * * trological objects, known as Navagrahas. Saturn, one of lakes. [93] [94] them, is known as "Shani", judges everyone based on the On 6 June 2013, scientists at the IAA-CSIC reported good and bad deeds performed in life.*[107]*[110] An- the detection of polycyclic aromatic hydrocarbons in cient Chinese and Japanese culture designated the planet the upper , a possible precursor for Saturn as the “earth star”(土星). This was based on life.*[95] On 23 June 2014, NASA claimed to have strong Five Elements which were traditionally used to classify evidence that nitrogen in the atmosphere of Titan came natural elements.*[111] from materials in the Oort cloud, associated with comets, In ancient Hebrew, Saturn is called 'Shabbathai'.*[112] and not from the materials that formed Saturn in earlier * Its angel is Cassiel. Its intelligence or beneficial spirit is times. [96] Agiel (layga) and its spirit (darker aspect) is Zazel (lzaz). Saturn's moon Enceladus has often been regarded as a po- In Ottoman Turkish, Urdu and Malay, its name is 'Zuhal', .زحل tential base for microbial life.*[97]*[98]*[99]*[100] Ev- derived from Arabic idence of this possibility includes the satellite's salt-rich particles having an “ocean-like”composition that indi- cates most of Enceladus's expelled ice comes from the 5.7.2 European observations (17th–19th evaporation of liquid salt water.*[101]*[102]*[103] centuries) In April 2014, NASA scientists reported the possible be- ginning of a new moon, within the A Ring, of the planet Saturn.*[104]

5.7 History of exploration

Main article:

There have been three main phases in the observation and exploration of Saturn. The first era was ancient observa- tions (such as with the naked eye), before the invention of the modern telescopes. Starting in the 17th century pro- gressively more advanced telescopic observations from Robert Hooke noted the shadows (a and b) cast by both the globe and the rings on each other in this drawing of Saturn in 1666. Earth have been made. The other type is visitation by spacecraft, either by orbiting or flyby. In the Saturn's rings require at least a 15-mm-diameter observations continue from the Earth (or Earth-orbiting telescope*[113] to resolve and thus were not known to observatories) and from the Cassini orbiter at Saturn. exist until Galileo first saw them in 1610.*[114]*[115] He thought of them as two moons on Saturn's * * 5.7.1 Ancient observations sides. [116] [117] It was not until Christiaan Huygens used greater telescopic magnification that this notion See also: Saturn (mythology) was refuted. Huygens discovered Saturn's moon Titan; Giovanni Domenico Cassini later discovered four other moons: Iapetus, Rhea, Tethys and Dione. In 1675, Saturn has been known since prehistoric times.*[105] In Cassini discovered the gap now known as the Cassini Di- ancient times, it was the most distant of the five known vision.*[118] planets in the Solar System (excluding Earth) and thus a major character in various mythologies. Babylonian No further discoveries of significance were made un- astronomers systematically observed and recorded the til 1789 when William Herschel discovered two further movements of Saturn.*[106] In ancient Roman mythol- moons, Mimas and Enceladus. The irregularly shaped satellite , which has a resonance with Titan, was ogy, the god Saturnus, from which the planet takes * its name, was the god of agriculture.*[107] The Ro- discovered in 1848 by a British team. [119] mans considered Saturnus the equivalent of the Greek In 1899 William Henry Pickering discovered Phoebe, god Cronus.*[107] The Greeks had made the outermost a highly irregular satellite that does not rotate syn- planet sacred to Cronus,*[108] and the Romans followed chronously with Saturn as the larger moons do.*[119] 5.7. HISTORY OF EXPLORATION 71

Phoebe was the first such satellite found and it takes more the small Maxwell Gap (a gap within the C Ring) and than a year to orbit Saturn in a retrograde orbit. During gap (a 42 km wide gap in the A Ring). the early 20th century, research on Titan led to the confir- mation in 1944 that it had a thick atmosphere – a feature unique among the Solar System's moons.*[120] Cassini–Huygens spacecraft On 1 July 2004, the Cassini–Huygens space probe per- 5.7.3 Modern NASA and ESA probes formed the SOI (Saturn Orbit Insertion) maneuver and entered orbit around Saturn. Before the SOI, Cassini had flyby already studied the system extensively. In June 2004, it had conducted a close flyby of Phoebe, sending back high-resolution images and data.

Pioneer 11 image of Saturn

Pioneer 11 carried out the first flyby of Saturn in Septem- ber 1979, when it passed within 20,000 km of the planet's Cassini ' s Titan flyby radio-signal studies (artist's concept) cloud tops. Images were taken of the planet and a few of its moons, although their resolution was too low to dis- Cassini's flyby of Saturn's largest moon, Titan, has cap- cern surface detail. The spacecraft also studied Saturn's tured radar images of large lakes and their coastlines with rings, revealing the thin F-ring and the fact that dark gaps numerous islands and mountains. The orbiter completed in the rings are bright when viewed at high phase angle two Titan flybys before releasing the Huygens probe on (towards the Sun), meaning that they contain fine light- 25 December 2004. Huygens descended onto the surface scattering material. In addition, Pioneer 11 measured the * of Titan on 14 January 2005, sending a flood of data dur- temperature of Titan. [121] ing the atmospheric descent and after the landing.*[123] Cassini has since conducted multiple flybys of Titan and Voyager flybys other icy satellites.

In November 1980, the Voyager 1 probe visited the Sat- urn system. It sent back the first high-resolution images of the planet, its rings and satellites. Surface features of various moons were seen for the first time. Voyager 1 performed a close flyby of Titan, increasing knowledge of the atmosphere of the moon. It proved that Titan's at- mosphere is impenetrable in visible wavelengths, there- fore no surface details were seen. The flyby changed the spacecraft's trajectory out from the plane of the Solar System.*[122]

Almost a year later, in August 1981, Voyager 2 continued Photograph of Earth and the Moon by Cassini, visible in the the study of the Saturn system. More close-up images bottom-right. of Saturn's moons were acquired, as well as evidence of changes in the atmosphere and the rings. Unfortunately, Since early 2005, scientists have been tracking lightning during the flyby, the probe's turnable camera platform on Saturn. The power of the lightning is approximately stuck for a couple of days and some planned imaging was 1,000 times that of lightning on Earth.*[124] lost. Saturn's gravity was used to direct the spacecraft's * In 2006, NASA reported that Cassini had found evidence trajectory towards Uranus. [122] of liquid water reservoirs that erupt in on Saturn's The probes discovered and confirmed several new satel- moon Enceladus. Images had shown jets of icy particles lites orbiting near or within the planet's rings, as well as being emitted into orbit around Saturn from vents in the 72 CHAPTER 5. SATURN

At Enceladus's south pole geysers spray water from many loca- tions along the tiger stripes.*[126]

capture an image of the Earth and the Moon (and, as well, Venus and Mars) as part of a natural light, multi-image portrait of the entire Saturn system. It was the first time Saturn's north polar vortex seen in (infrared) (animation) NASA informed the people of Earth that a long-distance photo was being taken in advance.*[134]

moon's south polar region. According to Andrew Inger- 5.8 Observation soll, California Institute of Technology, “Other moons in the Solar System have liquid-water oceans covered by kilometers of icy crust. What's different here is that pockets of liquid water may be no more than tens of me- ters below the surface.”*[125] Over 100 geysers have been identified on Enceladus.*[126] In May 2011, NASA scientists at an Enceladus Focus Group Conference re- ported that Enceladus“is emerging as the most habitable spot beyond Earth in the Solar System for life as we know it”.*[127]*[128] Cassini photographs have led to other significant discov- eries. They have revealed a previously undiscovered plan- etary ring, outside the brighter main rings of Saturn and inside the G and E rings. The source of this ring is believed to be the crashing of a meteoroid off two of Amateur telescopic view the moons of Saturn.*[129] In July 2006, Cassini im- ages provided evidence of hydrocarbon lakes near Titan's Saturn is the most distant of the five planets easily visible north pole, the presence of which were confirmed in Jan- to the naked eye, the other four being Mercury, Venus, uary 2007. In March 2007, additional images near Ti- Mars and Jupiter. (Uranus and occasionally are tan's north pole revealed hydrocarbon seas, the largest visible to the naked eye in dark skies.) Saturn appears of which is almost the size of the Caspian Sea.*[130] In to the naked eye in the night sky as a bright, yellowish October 2006, the probe detected an 8,000 km diame- point of light with an apparent magnitude of usually be- ter -like storm with an eyewall at Saturn's south tween +1 and 0. It takes approximately 29.5 years for the pole.*[131] planet to complete an entire circuit of the ecliptic against the background constellations of the zodiac. Most peo- From 2004 to 2 November 2009, the probe discovered ple will require an optical aid (very large binoculars or a and confirmed 8 new satellites. Its primary mission ended small telescope) that magnifies at least 30 times to achieve in 2008 when the spacecraft had completed 74 orbits an image of Saturn's rings, in which clear resolution is around the planet. The probe's mission was extended present.*[30]*[113] Twice every Saturnian year (roughly to September 2010 and then extended again to 2017, to * every 15 Earth years), the rings briefly disappear from study a full period of Saturn's seasons. [132] view, due to the way in which they are angled and because In April 2013 Cassini sent back images of a hurricane at they are so thin.*[135] Such a“disappearance”will next the planet's north pole 20 times larger than those found occur in 2025, but Saturn will be too close to the Sun for on Earth, with winds faster than 530 km/h.*[133] any ring-crossing observation to be possible.*[136] On 19 July 2013, Cassini was pointed towards Earth to Saturn and its rings are best seen when the planet is at, 5.9. IN CULTURE 73

Horner explain the seasonal nature of Saturnian occulta- tions:

This is the result of the fact that the moon’ s orbit around the Earth is tilted to the orbit of the Earth around the Sun – and so most of the time, the moon will pass above or below Sat- urn in the sky, and no occultation will occur. It is only when Saturn lies near the point that the moon’s orbit crosses the“plane of the ecliptic” that occultations can happen – and then they occur every time the moon swings by, until Sat- urn moves away from the crossing point.*[138]

5.9 In culture

Simulated appearance of Saturn as seen from Earth

or near, opposition, the configuration of a planet when it is at an of 180°, and thus appears opposite the Sun in the sky. A Saturnian opposition occurs every year—approximately every 378 days—and results in the planet appearing at its brightest. However, both the Earth and Saturn orbit the Sun on eccentric orbits, which means their distances from the Sun vary over time, and there- fore so do their distances from each other, hence varying Saturn, from a 1550 edition of Guido Bonatti's Liber astrono- the brightness of Saturn from one opposition to the other. miae Also, Saturn appears brighter when the rings are angled such that they are more visible. For example, during the Further information: Saturn in fiction opposition of 17 December 2002, Saturn appeared at its brightest due to a favorable orientation of its rings relative to the Earth,*[137] even though Saturn was closer to the • Saturn in astrology ( ) is the ruling planet of Earth and Sun in late 2003.*[137] and, traditionally, . • Saturn, the Bringer of Old Age is a movement in Gustav Holst's The Planets. • The Saturn family of rockets were developed by a team of mostly German rocket scientists led by Wernher von Braun to launch heavy payloads to Earth orbit and beyond.*[139] Originally proposed as a military satellite launcher, they were adopted as the launch vehicles for the program. • The day Saturday is named after the planet Sat- Saturn eclipses the Sun, as seen from Cassini. urn, which is derived from the Roman god of agriculture, Saturn (linked to the Greek god Also, from time to time Saturn is occulted by the Moon Cronus).*[140]*[141] (that is, the Moon covers up Saturn in the sky). As with all the planets in the Solar System, occultations of Sat- • In Saturn's Rings is an upcoming movie from direc- urn occur in“seasons”. Saturnian occultations will take tor Stephen van Vuuren about Saturn. It features place 12 or more times over a 12-month period, followed more than a million photographs of the planet as- by about a five-year period in which no such activity is sembled with various techniques. The film is ex- registered.*[138] Australian astronomy experts Hill and pected to be released in late 2014. 74 CHAPTER 5. SATURN

5.10 See also [9] Schmude, Richard W. Junior (2001). “Wideband pho- toelectric magnitude measurements of Saturn in 2000”. • (astronomy) Georgia Journal of Science. Archived from the original on 16 October 2007. Retrieved 14 October 2007. • Sixth planet (disambiguation) [10] Brainerd, Jerome James (24 November 2004). “Char- • Space exploration acteristics of Saturn”. The Astrophysics Spectator. Archived from the original on 5 October 2011. Retrieved 5 July 2010. 5.11 Notes [11] “General Information About Saturn”. Scienceray. 28 July 2011. Archived from the original on 5 October 2011. Retrieved 17 August 2011. [1] Orbital elements refer to the barycenter of the Saturn sys- tem and are the instantaneous osculating values at the pre- [12] Brainerd, Jerome James (6 October 2004).“Solar System cise J2000 epoch. Barycenter quantities are given be- Planets Compared to Earth”. The Astrophysics Spectator. cause, in contrast to the planetary centre, they do not ex- Archived from the original on 5 October 2011. Retrieved perience appreciable changes on a day-to-day basis from 5 July 2010. the motion of the moons. [13] Dunbar, Brian (29 November 2007). “NASA – Saturn” [2] Refers to the level of 1 bar atmospheric pressure . NASA. Archived from the original on 5 October 2011. Retrieved 21 July 2011.

[14] Cain, Fraser (3 July 2008). “Mass of Saturn”. Universe 5.12 References Today. Retrieved 17 August 2011.

[1] Walter, Elizabeth (21 April 2003). Cambridge Advanced [15] Brainerd, Jerome James (27 October 2004). “Giant Learner's Dictionary (Second ed.). Cambridge University Gaseous Planets”. The Astrophysics Spectator. Archived Press. ISBN 978-0-521-53106-1. from the original on 5 October 2011. Retrieved 5 July 2010. [2] Yeomans, Donald K. (13 July 2006).“HORIZONS Web- Interface for Saturn Barycenter (Major Body=6)". JPL [16] Russell, C. T. et al. (1997).“Saturn: and Horizons On-Line Ephemeris System. Retrieved 8 Au- Magnetosphere”. UCLA – IGPP Space Physics Center. gust 2007. – Select“Ephemeris Type: Orbital Elements” Archived from the original on 5 October 2011. Retrieved ,“Time Span: 2000-01-01 12:00 to 2000-01-02”.(“Tar- 29 April 2007. get Body: Saturn Barycenter”and“Center: Sun”should [17]“The Planets ('Giants')". Science Channel. 8 June 2004. be defaulted to.) [18] Piazza, Enrico.“Saturn's Moons”. Cassini, Equinox Mis- [3] Seligman, Courtney.“Rotation Period and Day Length”. sion. JPL NASA. Archived from the original on 5 October Archived from the original on 10 August 2011. Retrieved 2011. Retrieved 22 June 2010. 13 August 2009. [19] Munsell, Kirk (6 April 2005). “The Story of Saturn” “ [4] Williams, David R. (7 September 2006). Saturn Fact . NASA Jet Propulsion Laboratory; California Institute ” Sheet . NASA. Archived from the original on 21 August of Technology. Archived from the original on 22 August 2011. Retrieved 31 July 2007. 2011. Retrieved 7 July 2007. “ [5] The MeanPlane (Invariable plane) of the Solar Sys- [20] Melosh, H. Jay (2011). Planetary Surface Processes. ” tem passing through the barycenter . 3 April 2009. Cambridge Planetary Science 13. Cambridge University Archived from the original on 14 May 2009. Retrieved Press. p. 5. ISBN 0-521-51418-5. 10 April 2009. (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane) [21] “Saturn – The Most Beautiful Planet of our solar system” . Preserve Articles. 23 January 2011. Archived from the [6] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, original on 5 October 2011. Retrieved 24 July 2011. Michael F. et al. (2007). “Report of the IAU/IAG Working Group on cartographic coordinates and [22] Williams, David R. (16 November 2004). “Jupiter Fact rotational elements: 2006”. Celestial Mechan- Sheet”. NASA. Archived from the original on 5 October ics and Dynamical Astronomy 98 (3): 155–180. 2011. Retrieved 2 August 2007. Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- 007-9072-y. [23] Fortney, Jonathan J.; Nettelmann, Nadine (May 2010). “The Interior Structure, Composition, and Evolution of [7] “NASA: Solar System Exploration: Planets: Saturn: Giant Planets”. Space Science Reviews 152 (1–4): 423– Facts & Figures”. Solarsystem.nasa.gov. 22 March 2011. 447. arXiv:0912.0533. Bibcode:2010SSRv..152..423F. Archived from the original on 5 October 2011. Retrieved doi:10.1007/s11214-009-9582-x. 8 August 2011. [24] Dyches, Preston et al. (8 January 2015). “Scientists Pin- [8] "'Nature' (Saturn's fast spin determined from its gravita- point Saturn With Exquisite Accuracy”. NASA. Retrieved tional field and oblateness)". Nature. 2 February 2015. 9 January 2015. 5.12. REFERENCES 75

[25] Guillot, Tristan et al. (2009). “Saturn's Explo- [40] Martinez, Carolina (5 September 2005). “Cassini Dis- ration Beyond Cassini-Huygens”. In Dougherty, covers Saturn's Dynamic Clouds Run Deep”. NASA. Michele K.; Esposito, Larry W.; Krimigis, Stamatios Archived from the original on 5 October 2011. Retrieved M. Saturn from Cassini-Huygens. Springer Sci- 29 April 2007. ence+Business Media B.V. p. 745. arXiv:0912.2020. Bibcode:2009sfch.book..745G. doi:10.1007/978-1- [41] Orton, Glenn S. (September 2009). “Ground-Based 4020-9217-6_23. ISBN 978-1-4020-9216-9. Observational Support for Spacecraft Exploration of the Outer Planets”. Earth, Moon, and Planets 105 [26] Fortney, Jonathan J. (2004). “Looking into the (2–4): 143–152. Bibcode:2009EM&P..105..143O. Giant Planets”. Science 305 (5689): 1414–1415. doi:10.1007/s11038-009-9295-x. doi:10.1126/science.1101352. PMID 15353790. [42] Dougherty, Michele K.; Esposito, Larry W.; Krimigis, [27] Saumon, D.; Guillot, T. (July 2004). “Shock Stamatios M., eds. (2009). “Saturn from Cassini- Compression of Deuterium and the Interiors of Huygens”. Saturn from Cassini-Huygens (Springer): Jupiter and Saturn”. The Astrophysical Journal 162. Bibcode:2009sfch.book.....D. doi:10.1007/978-1- 609 (2): 1170–1180. arXiv:astro-ph/0403393. 4020-9217-6. ISBN 1-4020-9216-4. Bibcode:2004ApJ...609.1170S. doi:10.1086/421257. [43] Pérez-Hoyos, S.; Sánchez-Laveg, A.; French, R. G.; J. F., Rojas (2005). “Saturn's cloud struc- [28] “Saturn”. BBC. 2000. Archived from the original on ture and temporal evolution from ten years of Hub- 21 August 2011. Retrieved 19 July 2011. ble Space Telescope images (1994–2003)". Icarus [29] Faure, Gunter; Mensing, Teresa M. (2007). Introduction 176 (1): 155–174. Bibcode:2005Icar..176..155P. to planetary science: the geological perspective. Springer. doi:10.1016/j.icarus.2005.01.014. p. 337. ISBN 1-4020-5233-2. [44] Patrick Moore, ed., 1993 Yearbook of Astronomy, (Lon- don: W.W. Norton & Company, 1992), Mark Kidger, [30] “Saturn”. National Maritime Museum. Archived from “The 1990 Great White Spot of Saturn”, pp. 176–215. the original on 5 October 2011. Retrieved 6 July 2007. [45] Hamilton, Calvin J. (1997). “Voyager Saturn Science [31] “Structure of Saturn's Interior”. Windows to the Uni- Summary”. Solarviews. Archived from the original on 5 verse. Archived from the original on 21 August 2011. Re- October 2011. Retrieved 5 July 2007. trieved 19 July 2011. [46] Watanabe, Susan (27 March 2007). “Saturn's Strange [32] de Pater, Imke; Lissauer, Jack J. (2010). Planetary Sci- Hexagon”. NASA. Archived from the original on 1 ences (2nd ed.). Cambridge University Press. pp. 254– February 2010. Retrieved 6 July 2007. 255. ISBN 0-521-85371-0. [47] “Warm Polar Vortex on Saturn”. Merrillville Commu- [33] “NASA – Saturn”. NASA. 2004. Archived from the nity Planetarium. 2007. Archived from the original on 5 original on 21 August 2011. Retrieved 27 July 2007. October 2011. Retrieved 25 July 2007.

[34] “Hubble sees a flickering light display on Saturn”. [48] Godfrey, D. A. (1988). “A hexagonal feature ESA/Hubble Picture of the Week. Retrieved 20 May 2014. around Saturn's North Pole”. Icarus 76 (2): 335. Bibcode:1988Icar...76..335G. doi:10.1016/0019- [35] Saturn. Universe Guide. Retrieved 29 March 2009. 1035(88)90075-9.

[36] Guillot, Tristan (1999). “Interiors of Giant Plan- [49] Sanchez-Lavega, A. et al. (1993).“Ground-based obser- ets Inside and Outside the Solar System”. Sci- vations of Saturn's north polar SPOT and hexagon”. Sci- ence 286 (5437): 72–77. Bibcode:1999Sci...286...72G. ence 260 (5106): 329–32. Bibcode:1993Sci...260..329S. doi:10.1126/science.286.5437.72. PMID 10506563. doi:10.1126/science.260.5106.329. PMID 17838249. [50] Overbye, Dennis (6 August 2014). “Storm Chasing on [37] Courtin, R. et al. (1967). “The Composition of Saturn's Saturn”. New York Times. Retrieved 6 August 2014. Atmosphere at Temperate Northern Latitudes from Voy- ager IRIS spectra”. Bulletin of the American Astronomical [51] “New images show Saturn's weird hexagon cloud”. Society 15: 831. Bibcode:1983BAAS...15..831C. MSNBC. 12 December 2009. Archived from the origi- nal on 5 October 2011. Retrieved 29 September 2011. [38] Cain, Fraser (22 January 2009).“Atmosphere of Saturn”. Universe Today. Archived from the original on 5 October [52] Godfrey, D. A. (9 March 1990). “The Rotation 2011. Retrieved 20 July 2011. Period of Saturn's Polar Hexagon”. Science 247 (4947): 1206–1208. Bibcode:1990Sci...247.1206G. [39] Guerlet, S.; Fouchet, T.; Bézard, B. (November 2008). doi:10.1126/science.247.4947.1206. PMID 17809277. Charbonnel, C.; Combes, F.; Samadi, R., eds. “Ethane, acetylene and propane distribution in Sat- [53] Baines, Kevin H. et al. (December 2009). “Sat- urn's stratosphere from Cassini/CIRS limb observations” urn's north polar cyclone and hexagon at depth revealed . SF2A-2008: Proceedings of the Annual meeting of by Cassini/VIMS”. Planetary and Space Science 57 the French Society of Astronomy and Astrophysics: 405. (14–15): 1671–1681. Bibcode:2009P&SS...57.1671B. Bibcode:2008sf2a.conf..405G. doi:10.1016/j.pss.2009.06.026. 76 CHAPTER 5. SATURN

[54] , Philip (19 May 2006). “Geometric whirlpools re- [68] Benton, Julius (2006). Saturn and how to observe it. As- vealed”. Nature. doi:10.1038/news060515-17. Bizarre tronomers' observing guides (11th ed.). Springer Science geometric shapes that appear at the centre of swirling vor- & Business. p. 136. ISBN 1-85233-887-3. tices in planetary atmospheres might be explained by a simple experiment with a bucket of water but correlating [69]“Scientists Find That Saturn's Rotation Period is a Puzzle” this to Saturn's pattern is by no means certain. . NASA. 28 June 2004. Archived from the original on 21 August 2011. Retrieved 22 March 2007. [55] Aguiar, Ana C. Barbosa et al. (April 2010). “A laboratory model of Saturn's North Polar Hexagon”. [70] Cain, Fraser. "Saturn.”Universe Today. 30 June 2008. Icarus 206 (2): 755–763. Bibcode:2010Icar..206..755B. Retrieved 17 August 2011. Archived 5 October 2011 at doi:10.1016/j.icarus.2009.10.022. Retrieved 20 Febru- WebCite ary 2013. Laboratory experiment of spinning disks in a liquid solution forms vortices around a stable hexagonal [71] “Enceladus Geysers Mask the Length of Saturn's Day” pattern similar to that of Saturn's. (Press release). NASA Jet Propulsion Laboratory. 22 March 2007. Retrieved 22 March 2007. Archived 5 Oc- [56] Sánchez-Lavega, A. et al. (8 October 2002). tober 2011 at WebCite “Hubble Space Telescope Observations of the Atmo- spheric Dynamics in Saturn's South Pole from 1997 to [72] Gurnett, D. A. et al. (2007). “The Variable Rotation Pe- 2002”. Bulletin of the American Astronomical Soci- riod of the Inner Region of Saturn's Plasma Disc”. Science ety 34. American Astronomical Society. p. 857. 316 (5823): 442–5. Bibcode:2007Sci...316..442G. Bibcode:2002DPS....34.1307S. Retrieved 6 July 2007. doi:10.1126/science.1138562. PMID 17379775.

[57] “NASA catalog page for image PIA09187”. NASA [73] , J. D.; Schubert, G. (2007). “Sat- Planetary Photojournal. Archived from the original on 5 urn's gravitational field, internal rotation and October 2011. Retrieved 23 May 2007. interior structure”. Science 317 (5843): 1384–1387. Bibcode:2007Sci...317.1384A. [58] “Huge 'hurricane' rages on Saturn”. BBC News. 10 doi:10.1126/science.1144835. PMID 17823351. November 2006. Archived from the original on 5 October 2011. Retrieved 29 September 2011. [74] Poulet F. et al. (2002). “The Com- position of Saturn's Rings”. Icarus 160 [59] “NASA Sees into the Eye of a Monster Storm on Saturn” (2): 350. Bibcode:2002Icar..160..350P. . NASA. 9 November 2006. Archived from the original doi:10.1006/icar.2002.6967. on 5 October 2011. Retrieved 20 November 2006. [75] Shafiq, Muhammad (2005). “Dusty Plasma Response to [60] “A Hurricane Over the South Pole of Saturn”. NASA. a Moving Test Change” (PDF). Retrieved 25 July 2007. NASA. 13 November 2006. Retrieved 1 May 2013. [76] Spahn, F. et al. (2006). “Cassini Dust Mea- [61] “Cassini Image Shows Saturn Draped in a String of surements at Enceladus and Implications for the Pearls” (Press release). Carolina Martinez , NASA. 10 Origin of the E Ring”. Science 311 (5766): November 2006. Retrieved 3 March 2013. 1416–1418. Bibcode:2006Sci...311.1416S. [62] McDermott, Matthew (2000). “Saturn: Atmosphere doi:10.1126/science.1121375. PMID 16527969. and Magnetosphere”. Thinkquest Internet Challenge. [77] “The Real Lord of the Rings”. Science@NASA. 12 Febru- Archived from the original on 5 October 2011. Retrieved ary 2002. Archived from the original on 5 October 2011. 15 July 2007. Retrieved 24 August 2011. [63] “Voyager – Saturn's Magnetosphere”. NASA Jet Propul- sion Laboratory. 18 October 2010. Archived from the [78] “Age and Fate of Saturn's Rings” (PD). Creation Con- original on 5 October 2011. Retrieved 19 July 2011. cepts. Retrieved 23 July 2011.

[64] Atkinson, Nancy (14 December 2010).“Hot Plasma Ex- [79] Cowen, Rob (7 November 1999). “Largest known plan- plosions Inflate Saturn's Magnetic Field”. Universe To- etary ring discovered”. Science News. Archived from the day. Archived from the original on 5 October 2011. Re- original on 5 October 2011. Retrieved 9 April 2010. trieved 24 August 2011. [80] Russell, Randy (7 June 2004).“Saturn Moons and Rings” [65] Russell, Randy (3 June 2003). “Saturn Magnetosphere . Windows to the Universe. Archived from the original on Overview”. Windows to the Universe. Archived from 5 October 2011. Retrieved 19 July 2011. the original on 5 October 2011. Retrieved 19 July 2011. [81] NASA Jet Propulsion Laboratory (3 March 2005). [66] Cain, Fraser (26 January 2009).“Orbit of Saturn”. Uni- “NASA's Cassini Spacecraft Continues Making New Dis- verse Today. Archived from the original on 5 October coveries”. ScienceDaily. Archived from the original on 2011. Retrieved 19 July 2011. 5 October 2011. Retrieved 19 July 2011.

[67] Jean Meeus, Astronomical Algorithms (Richmond, VA: [82] Tiscareno, Matthew (17 July 2013). “The population of Willmann-Bell, 1998). Average of the nine extremes on propellers in Saturn's A Ring”. Cornell University Li- p 273. All are within 0.02 au of the averages. brary. Retrieved 17 July 2013. 5.12. REFERENCES 77

[83] Wall, Mike (21 June 2011). “Saturn's 'Ice Queen' Moon [99] Spotts, Peter N. (28 September 2005). “Life beyond Shimmers in New Photo”. Space.com. Archived Earth? Potential solar system sites pop up”. USA Today. from the original on 5 October 2011. Retrieved 19 July Archived from the original on 5 October 2011. Retrieved 2011. 21 July 2011.

[84] Brunier, Serge (2005). Solar System Voyage. Cambridge [100] Pili, Unofre (9 September 2009). “Enceladus: Sat- University Press. p. 164. ISBN 978-0-521-80724-1. urn′s Moon, Has Liquid Ocean of Water”. Scienceray. Archived from the original on 5 October 2011. Retrieved [85] Jones, G. H. et al. (7 March 2008). “The Dust 21 July 2011. Halo of Saturn's Largest Icy Moon, Rhea”. Science 319 (5868): 1380–1384. Bibcode:2008Sci...319.1380J. [101] “Strongest evidence yet indicates Enceladus hiding salt- doi:10.1126/science.1151524. PMID 18323452. water ocean”. Physorg. 22 June 2011. Archived from the original on 5 October 2011. Retrieved 19 July 2011. [86] Atkinson, Nancy (26 November 2010). “Tenuous Oxy- [102] Kaufman, Marc (22 June 2011). “Saturn′s moon Ence- gen Atmosphere Found Around Saturn's Moon Rhea”. ladus shows evidence of an ocean beneath its surface”. Universe Today. Archived from the original on 5 October Washington Post. Archived from the original on 5 October 2011. Retrieved 20 July 2011. 2011. Retrieved 19 July 2011. [87] NASA (30 November 2010). “Thin air: Oxygen atmo- [103] Greicius, Tony et al. (22 June 2011). “Cassini Captures sphere found on Saturn's moon Rhea”. ScienceDaily. Ocean-Like Spray at Saturn Moon”. NASA. Archived Archived from the original on 5 October 2011. Retrieved from the original on 5 October 2011. Retrieved 17 23 July 2011. September 2011.

[88] “Oxygen found on Saturn moon: NASA spacecraft dis- [104] Platt, Jane et al. (14 April 2014).“NASA Cassini Images covers Rhea has thin atmosphere rich in O2”. Daily Mail. May Reveal Birth of a Saturn Moon”. NASA. Retrieved 26 November 2010. Archived from the original on 5 Oc- 14 April 2014. tober 2011. Retrieved 23 July 2011. [105] “Saturn > Observing Saturn”. National Maritime Mu- [89] Ryan, Clare (26 November 2010). “Cassini reveals oxy- seum. Archived from the original on 22 April 2007. Re- gen atmosphere of Saturn′s moon Rhea”. UCL Mullard trieved 6 July 2007. Space Science Laboratory. Archived from the original on 5 October 2011. Retrieved 23 July 2011. [106] Sachs, A. (2 May 1974). “Babylonian Observational As- tronomy”. Philosophical Transactions of the Royal So- [90] “Saturn's Known Satellites”. Department of Terres- ciety of London (Royal Society of London) 276 (1257): trial Magnetism. Archived from the original on 5 October 43–50 [45 & 48–9]. Bibcode:1974RSPTA.276...43S. 2011. Retrieved 22 June 2010. doi:10.1098/rsta.1974.0008. JSTOR 74273.

[91] “Cassini Finds Hydrocarbon Rains May Fill Titan Lakes”[107] “Starry Night Times”. Imaginova Corp. 2006. Archived . ScienceDaily. 30 January 2009. Archived from the orig- from the original on 21 August 2011. Retrieved 5 July inal on 5 October 2011. Retrieved 19 July 2011. 2007.

[92] “Voyager – Titan”. NASA Jet Propulsion Laboratory. 18 [108] , James (1998). The History and Practice of Ancient October 2010. Archived from the original on 5 October Astronomy. Oxford University Press. pp. 296–7. ISBN 2011. Retrieved 19 July 2011. 978-0-19-509539-5. “ ” [93] “Evidence of hydrocarbon lakes on Titan”. MSNBC. As- [109] Greek Names of the Planets . Retrieved 14 July 2012. sociated Press. 25 July 2006. Archived from the original The Greek name of the planet Saturn is Kronos. The Titan on 5 October 2011. Retrieved 19 July 2011. Cronus was the father of Zeus, while Saturn was the Ro- man God of agriculture. See also the Greek article about [94] “Hydrocarbon lake finally confirmed on Titan”. Cosmos the planet. Magazine. 31 July 2008. Archived from the original on 5 [110] “Popular Miscellany – Superstitions about Saturn”. The October 2011. Retrieved 19 July 2011. Monthly: 862. April 1893. “ [95] López-Puertas, Manuel (6 June 2013). PAH's in Titan's [111] ‹The template Chinaplanetnames is being considered for ” Upper Atmosphere . CSIC. Retrieved 6 June 2013. deletion.› China: De Groot, Jan Jakob Maria (1912). Religion in [96] Dyches, Preston et al. (23 June 2014). “Titan's Building China: universism. a key to the study of Taoism and Con- Blocks Might Pre-date Saturn”. NASA. Retrieved 24 June fucianism. American lectures on the history of religions 10 2014. (G. P. Putnam's Sons). p. 300. Retrieved 2010-01-08. [97] NASA (21 April 2008). “Could There Be Life On Sat- Japan: Crump, Thomas (1992). The Japanese numbers urn's Moon Enceladus?". ScienceDaily. Archived from game: the use and understanding of numbers in modern the original on 5 October 2011. Retrieved 19 July 2011. Japan. Nissan Institute/Routledge Japanese studies series (Routledge). pp. 39–40. ISBN 0415056098. [98] Madrigal, Alexis (24 June 2009). “Hunt for Life on Sat- Korea: Hulbert, Homer Bezaleel (1909). The passing of urnian Moon Heats Up”. Wired Science. Archived from Korea. Doubleday, Page & company. p. 426. Retrieved the original on 5 October 2011. Retrieved 19 July 2011. 2010-01-08. 78 CHAPTER 5. SATURN

[112] Cessna, Abby (15 November 2009). “When Was Sat- [128] Kazan, Casey (2 June 2011).“Saturn's Enceladus Moves urn Discovered?". Universe Today. Archived from the to Top of“Most-Likely-to-Have-Life”List”. The Daily original on 5 October 2011. Retrieved 21 July 2011. . Archived from the original on 21 August 2011. Retrieved 3 June 2011. [113] , Jack (1998). “Saturn in Binoculars”. The Denver Astronomical Society. Archived from the original [129] Shiga, David (20 September 2007). “Faint new ring dis- on 21 August 2011. Retrieved 3 September 2008. covered around Saturn”. NewScientist.com. Archived from the original on 21 August 2011. Retrieved 8 July [114] Chan, Gary (2000). “Saturn: History Timeline”. 2007. Archived from the original on 21 August 2011. Retrieved 16 July 2007. [130] Rincon, Paul (14 March 2007). “Probe reveals seas on Saturn moon”. BBC. Archived from the original on 5 [115] Cain, Fraser (3 July 2008).“History of Saturn”. Universe October 2011. Retrieved 26 September 2007. Today. Archived from the original on 5 October 2011. Retrieved 24 July 2011. [131] Rincon, Paul (10 November 2006). “Huge 'hurricane' [116] Cain, Fraser (7 July 2008).“Interesting Facts About Sat- rages on Saturn”. BBC. Archived from the original on 5 urn”. Universe Today. Archived from the original on 5 October 2011. Retrieved 12 July 2007. October 2011. Retrieved 17 September 2011. [132] “Mission overview – introduction”. Cassini Solstice Mis- [117] Cain, Fraser (27 November 2009). “Who Discovered sion. NASA / JPL. 2010. Archived from the original on Saturn?". Universe Today. Archived from the original on 21 August 2011. Retrieved 23 November 2010. 5 November 2011. Retrieved 17 September 2011. [133] “Massive storm at Saturn's north pole”. 3 News NZ. 30 [118] Micek, Catherine. “Saturn: History of Discoveries”. April 2013. Archived from the original on 21 August 2011. Retrieved 15 July 2007. [134] Overbye, Dennis (12 November 2013).“The View From Saturn”. New York Times. Retrieved 12 November 2013. [119] , Samuel G. (April 1946). “The names of the satellites”. Popular Astronomy 54: 122–130. [135] “Why do Saturn's rings Sometimes Disappear?". Google Bibcode:1946PA.....54..122B. News. Retrieved 4 August 2013.

[120] Kuiper, Gerard P. (November 1944). “Titan: a [136] “Saturn's Rings Edge-On”. Classical Astronomy. 2013. Satellite with an Atmosphere”. Astrophysical Jour- Retrieved 4 August 2013. nal 100: 378–388. Bibcode:1944ApJ...100..378K. doi:10.1086/144679. [137] Schmude, Richard W Jr. (2003). “Saturn in 2002–03” . Georgia Journal of Science. Archived from the original [121]“The Pioneer 10 & 11 Spacecraft”. Mission Descriptions. on 16 October 2007. Retrieved 14 October 2007. Archived from the original on 30 January 2006. Retrieved 5 July 2007. [138] Tanya Hill et al. (9 May 2014).“Bright Saturn will blink out across Australia – for an hour, anyway”. The Con- [122] “Missions to Saturn”. The Planetary Society. 2007. versation. Retrieved 11 May 2014. Archived from the original on 21 August 2011. Retrieved 24 July 2007. [139] Bilstein, Roger E. (1999). Stages to Saturn: A Technolog- [123] Lebreton, Jean-Pierre et al. (December 2005). ical History of the Apollo/Saturn . DIANE “An overview of the descent and landing of Publishing. p. 37. ISBN 0-7881-8186-6. the Huygens probe on Titan”. Nature 438 [140] Plotner, Tammy (22 February 2008). “Time to Observe (7069): 758–764. Bibcode:2005Natur.438..758L. Saturn – Opposition Occurs February 23!". Universe To- doi:10.1038/nature04347. PMID 16319826. day. Archived from the original on 5 October 2011. Re- [124] “Astronomers Find Giant Lightning Storm At Saturn”. trieved 19 July 2011. ScienceDaily LLC. 2007. Archived from the original on 21 August 2011. Retrieved 27 July 2007. [141] Reis, Ricardo Cardoso; Jones, Jane H. “Saturn: The Ringed Planet” (PDF). IAU. Retrieved 23 July 2011. [125] Pence, Michael (9 March 2006). “NASA's Cassini Dis- covers Potential Liquid Water on Enceladus”. NASA Jet Propulsion Laboratory. Archived from the original on 21 August 2011. Retrieved 3 June 2011. 5.13 Further reading

[126] Dyches, Preston et al. (28 July 2014).“Cassini Spacecraft • Lovett, L. et al. (2006). Saturn: A New View. New Reveals 101 Geysers and More on Icy Saturn Moon”. York: Harry N. Abrams, Inc. ISBN 978-0-8109- NASA. Retrieved 29 July 2014. 3090-2. [127] Lovett, Richard A. (31 May 2011). “Enceladus named sweetest spot for alien life”. Nature (Nature). • Karttunen, H. et al. (2007). Fundamental Astron- doi:10.1038/news.2011.337. Archived from the original omy (5th ed.). New York: Springer. ISBN 978-3- on 5 October 2011. Retrieved 3 June 2011. 540-34143-7. 5.14. EXTERNAL LINKS 79

5.14 External links

• Saturn profile at NASA's Solar System Exploration site • Saturn Fact Sheet, by NASA

• Gazeteer of Planetary Nomenclature – Saturn (USGS) • Cassini–Huygens mission to Saturn, by NASA

• Research News about Saturn • General information about Saturn

• Studies on the Rings of Saturn • Astronomy Cast: Saturn

• Saturn in Daytime (12 inch telescope) • Saturn 'Rev 175' Raw Preview

• Haese, Paul. “Capturing Saturn”. Sixty Symbols. Brady Haran for the University of Nottingham. Chapter 6

Uranus

This article is about the planet. For other uses, see bit.*[18] Sir William Herschel announced its discovery Uranus (disambiguation). on March 13, 1781, expanding the known boundaries of the Solar System for the first time in history. Uranus was the first planet discovered with a telescope. Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest in the Solar System. Uranus is similar in composi- tion to Neptune, and both have different bulk chemical 6.1.1 Discovery composition from that of the larger gas giants Jupiter and Saturn. Therefore, astronomers increasingly place them Uranus had been observed on many occasions before its in a separate category called "ice giants". Uranus's at- recognition as a planet, but it was generally mistaken for mosphere, although similar to Jupiter's and Saturn's in its a star. Possibly the earliest known observation was by primary composition of hydrogen and helium, contains Hipparchos, who in 128BC may have recorded the planet more "ices", such as water, ammonia, and methane, along as a star for his that was later incorpo- * with traces of other hydrocarbons.*[11] It is the coldest rated into Ptolemy's Almagest. [19] The earliest definite planetary atmosphere in the Solar System, with a mini- sighting was in 1690 when John observed it at mum temperature of 49 K (−224.2 °C), and has a com- least six times, cataloguing it as 34 Tauri. The French plex, layered cloud structure, with water thought to make astronomer Pierre Lemonnier observed Uranus at least * up the lowest clouds, and methane the uppermost layer of twelve times between 1750 and 1769, [20] including on clouds.*[11] The interior of Uranus is mainly composed four consecutive nights. * of ices and rock. [10] Sir William Herschel observed Uranus on March 13, Uranus is the only planet whose name is derived from a 1781 from the garden of his house at 19 New King Street figure from Greek mythology rather than Roman mythol- in Bath, Somerset, England (now the Herschel Museum ogy, from the Latinized version of the Greek god of the of Astronomy),*[21] and initially reported it (on April 26, sky, Ouranos. Like the other giant planets, Uranus has a 1781) as a comet.*[22] Herschel“engaged in a series of * ring system, a magnetosphere, and numerous moons. The observations on the parallax of the fixed stars”, [23] us- Uranian system has a unique configuration among those ing a telescope of his own design. of the planets because its axis of rotation is tilted side- He recorded in his journal “In the quartile near ζ Tauri ways, nearly into the plane of its revolution about the Sun. ... either [a] Nebulous star or perhaps a comet”.*[24] On Its north and south poles therefore lie where most other March 17, he noted, “I looked for the Comet or Nebu- * planets have their . [16] In 1986, images from lous Star and found that it is a Comet, for it has changed Voyager 2 showed Uranus as an almost featureless planet its place”.*[25] When he presented his discovery to the in visible light, without the cloud bands or storms associ- Royal Society, he continued to assert that he had found a * ated with the other giant planets. [16] Observations from comet, but also implicitly compared it to a planet:*[26] Earth have shown seasonal change and increased weather activity as Uranus approached its equinox in 2007. The wind speeds on Uranus can reach 250 metres per second “The power I had on when I first saw the (900 km/h, 560 mph).*[17] comet was 227. From experience I know that the diameters of the fixed stars are not propor- tionally magnified with higher powers, as plan- ets are; therefore I now put the powers at 460 6.1 History and 932, and found that the diameter of the comet increased in proportion to the power, as Though Uranus is visible to the naked eye like the five it ought to be, on the supposition of its not being classical planets, it was never recognized as a planet by a fixed star, while the diameters of the stars to ancient observers because of its dimness and slow or- which I compared it were not increased in the

80 6.1. HISTORY 81

same ratio. Moreover, the comet being magni- star, which I had the honour of pointing out to them in fied much beyond what its light would admit of, March 1781, is a Primary Planet of our Solar System.” appeared hazy and ill-defined with these great *[31] In recognition of his achievement, King George III powers, while the stars preserved that lustre and gave Herschel an annual stipend of £200 on condition that distinctness which from many thousand obser- he move to Windsor so that the Royal Family could look vations I knew they would retain. The sequel through his telescopes.*[32] has shown that my surmises were well-founded, this proving to be the Comet we have lately ob- served”. 6.1.2 Naming

Maskelyne asked Herschel to“do the astronomical world the faver [sic] to give a name to your planet, which is en- tirely your own, [and] which we are so much obliged to you for the discovery of”.*[33] In response to Maske- lyne's request, Herschel decided to name the object Georgium Sidus (George's Star), or the“Georgian Planet” in honour of his new patron, King George III.*[34] He explained this decision in a letter to Joseph Banks:*[31]

In the fabulous ages of ancient times the appellations of Mercury, Venus, Mars, Jupiter and Saturn were given to the Planets, as be- ing the names of their principal heroes and di- vinities. In the present more philosophical era it would hardly be allowable to have recourse to the same method and call it Juno, Pallas, Apollo or Minerva, for a name to our new heav- enly body. The first consideration of any par- ticular event, or remarkable incident, seems to be its chronology: if in any future age it should be asked, when this last-found Planet was dis- covered? It would be a very satisfactory answer to say, 'In the reign of King George the Third'.

Replica of the telescope used by Herschel to discover Uranus (William Herschel Museum, Bath)

Herschel notified the Astronomer Royal, Nevil Maske- lyne, of his discovery and received this flummoxed reply from him on April 23: “I don't know what to call it. It is as likely to be a regular planet moving in an orbit nearly circular to the sun as a Comet moving in a very eccentric ellipsis. I have not yet seen any coma or tail to it”.*[27] Although Herschel continued to describe his new object as a comet, other astronomers had already begun to sus- pect otherwise. Russian astronomer Anders Johan Lex- ell was the first to compute the orbit of the new ob- ject*[28] and its nearly circular orbit led him to a con- clusion that it was a planet rather than a comet. Berlin astronomer Johann Elert described Herschel's dis- covery as “a moving star that can be deemed a hitherto unknown planet-like object circulating beyond the orbit of Saturn”.*[29] Bode concluded that its near-circular orbit was more like a planet than a comet.*[30] The object was soon universally accepted as a new planet. By 1783, Herschel acknowledged this to Royal Society president Joseph Banks:“By the observation of the most eminent Astronomers in Europe it appears that the new William Herschel, discoverer of Uranus 82 CHAPTER 6. URANUS

Herschel's proposed name was not popular outside Britain, and alternatives were soon proposed. As- tronomer Jérôme Lalande proposed that it be named Herschel in honour of its discoverer.*[35] Swedish as- tronomer Erik Prosperin proposed the name Neptune, which was supported by other astronomers who liked the idea to commemorate the victories of the British Royal Naval fleet in the course of the American Revolutionary War by calling the new planet even Neptune George III or Neptune Great Britain.*[28] Bode opted for Uranus, the Latinized version of the Greek god of the sky, Ouranos. Bode argued that just as Saturn was the father of Jupiter, the new planet should be named after the father of Sat- urn.*[32]*[36]*[37] In 1789, Bode's Royal Academy col- league Martin Klaproth named his newly discovered - ement in support of Bode's choice.*[38] Ulti- mately, Bode's suggestion became the most widely used, and became universal in 1850 when HM Nautical Al- manac Office, the final holdout, switched from using Uranus revolves around the Sun once every 84 Earth years. Its * Georgium Sidus to Uranus. [36] average distance from the Sun is roughly 3 billion km (about 20 AU)

6.1.3 Name

Uranus is named after the ancient Greek deity of the sky Uranus (Ancient Greek: Οὐρανός), the father of Cronus (Saturn) and grandfather of Zeus (Jupiter), which in Latin became "Ūranus”.*[1] It is the only planet whose name is derived from a figure from Greek mythology rather than Roman mythology. The adjective of Uranus is“Uranian” .*[39] The pronunciation of the name Uranus preferred among astronomers is /ˈjʊərənəs/,*[2] with stress on the first syllable as in Latin Ūranus, in contrast to the collo- quial /jʊˈreɪnəs/, with stress on the second syllable and a long a, though both are considered acceptable.*[lower- alpha 4] Uranus has two . The first to be proposed, ♅,*[lower-alpha 5] was suggested by Lalande in 1784. In a letter to Herschel, Lalande described it as “un globe surmonté par la première lettre de votre nom”(“a globe surmounted by the first letter of your A 1998 false-colour near-infrared image of Uranus showing surname”).*[35] A later proposal, ,*[lower-alpha 6] cloud bands, rings, and moons obtained by the Hubble Space is a hybrid of the symbols for Mars and the Sun be- Telescope's NICMOS camera. cause Uranus was the Sky in Greek mythology, which was thought to be dominated by the combined powers of the on Uranus, at about 20 times the distance from the Sun Sun and Mars.*[41] In Chinese, Japanese, Korean, and compared to Earth, it is about 1/400 the intensity of light Vietnamese, its name is literally translated as the “sky on Earth.*[45] Its orbital elements were first calculated king star”(天王星).*[42]*[43] in 1783 by Pierre-Simon Laplace.*[46] With time, dis- crepancies began to appear between the predicted and observed orbits, and in 1841, first 6.2 Orbit and rotation proposed that the differences might be due to the gravita- tional tug of an unseen planet. In 1845, Urbain Le Verrier Uranus orbits the Sun once every 84 Earth years. Its aver- began his own independent research into Uranus's orbit. age distance from the Sun is roughly 3 billion km (about On September 23, 1846, Johann Gottfried Galle located a new planet, later named Neptune, at nearly the position 20 AU). The variation of that distance is greater than that * of any other planet, at 1.8 AU.*[44] The intensity of sun- predicted by Le Verrier. [47] light reduces quadratically with distance, and therefore The rotational period of the interior of Uranus is 17 6.3. INTERNAL STRUCTURE 83 hours, 14 minutes, clockwise (retrograde). As on all giant for Jupiter.*[12] At opposition, Uranus is visible to the planets, its upper atmosphere experiences strong winds naked eye in dark skies, and becomes an easy target even in the direction of rotation. At some latitudes, such as in urban conditions with binoculars.*[6] In larger ama- about 60 degrees south, visible features of the atmosphere teur telescopes with an objective diameter of between 15 move much faster, making a full rotation in as little as 14 and 23 cm, Uranus appears as a pale cyan disk with dis- hours.*[48] tinct limb darkening. With a large telescope of 25 cm or wider, cloud patterns, as well as some of the larger satel- lites, such as and , may be visible.*[56] 6.2.1 Axial tilt

Uranus has an axial tilt of 97.77°, so its axis of rotation is 6.3 Internal structure approximately parallel with the plane of the Solar System. This gives it seasonal changes completely unlike those of the other major planets. Other planets can be visualized to rotate like tilted spinning tops on the plane of the So- lar System, but Uranus rotates more like a tilted rolling ball. Near the time of Uranian , one pole faces the Sun continuously and the other one faces away. Only a narrow strip around the equator experiences a rapid day– night cycle, but with the Sun low over the horizon as in Earth's polar regions. At the other side of Uranus's orbit the orientation of the poles towards the Sun is reversed. Each pole gets around 42 years of continuous sunlight, followed by 42 years of darkness.*[49] Near the time of the , the Sun faces the equator of Uranus giv- ing a period of day–night cycles similar to those seen on most of the other planets. Uranus reached its most recent equinox on December 7, 2007.*[50]*[51] Size comparison of Earth and Uranus One result of this axis orientation is that, averaged over the Uranian year, the polar regions of Uranus receive a greater energy input from the Sun than its equatorial re- gions. Nevertheless, Uranus is hotter at its equator than at its poles. The underlying mechanism that causes this is unknown. The reason for Uranus's unusual axial tilt is also not known with certainty, but the usual specula- tion is that during the formation of the Solar System, an Earth-sized collided with Uranus, causing the skewed orientation.*[52] Uranus's south pole was pointed almost directly at the Sun at the time of Voyager 2's flyby in 1986. The labelling of this pole as “south”uses the definition currently endorsed by the International Astro- nomical Union, namely that the north pole of a planet or satellite is the pole that points above the invariable plane of the Solar System, regardless of the direction the planet Diagram of the interior of Uranus is spinning.*[53]*[54] A different convention is some- times used, in which a body's north and south poles are Uranus's mass is roughly 14.5 times that of Earth, mak- defined according to the right-hand rule in relation to the ing it the least massive of the giant planets. Its di- direction of rotation.*[55] In terms of this system it was ameter is slightly larger than Neptune's at roughly four Uranus's north pole that was in sunlight in 1986. times that of Earth. A resulting density of 1.27 g/cm3 makes Uranus the second least dense planet, after Sat- urn.*[8]*[9] This value indicates that it is made pri- 6.2.2 Visibility marily of various ices, such as water, ammonia, and methane.*[10] The total mass of ice in Uranus's interior From 1995 to 2006, Uranus's apparent magnitude fluc- is not precisely known, because different figures emerge tuated between +5.6 and +5.9, placing it just within the depending on the model chosen; it must be between 9.3 limit of naked eye visibility at +6.5.*[12] Its angular di- and 13.5 Earth masses.*[10]*[57] Hydrogen and helium ameter is between 3.4 and 3.7 arcseconds, compared with constitute only a small part of the total, with between 0.5 16 to 20 arcseconds for Saturn and 32 to 45 arcseconds and 1.5 Earth masses.*[10] The remainder of the non-ice 84 CHAPTER 6. URANUS

mass (0.5 to 3.7 Earth masses) is accounted for by rocky 6.3.1 Internal heat material.*[10] The standard model of Uranus's structure is that it con- Uranus's internal heat appears markedly lower than that of the other giant planets; in astronomical terms, it has a sists of three layers: a rocky (silicate/iron–nickel) core * * in the centre, an icy mantle in the middle and an outer low thermal flux. [17] [64] Why Uranus's internal tem- gaseous hydrogen/helium envelope.*[10]*[58] The core perature is so low is still not understood. Neptune, which is relatively small, with a mass of only 0.55 Earth masses is Uranus's near twin in size and composition, radiates 2.61 times as much energy into space as it receives from and a radius less than 20% of Uranus's; the mantle * comprises its bulk, with around 13.4 Earth masses, and the Sun, [17] but Uranus radiates hardly any excess heat the upper atmosphere is relatively insubstantial, weigh- at all. The total power radiated by Uranus in the far in- frared (i.e. heat) part of the spectrum is 1.06 ± 0.08 times ing about 0.5 Earth masses and extending for the last * * * * the solar energy absorbed in its atmosphere. [11] [65] 20% of Uranus's radius. [10] [58] Uranus's core density 2 is around 9 g/cm3, with a pressure in the center of Uranus's heat flux is only 0.042 ± 0.047 W/m , which is lower than the internal heat flux of Earth of about 0.075 8 million bars (800 GPa) and a temperature of about 2 * 5000 K.*[57]*[58] The ice mantle is not in fact com- W/m . [65] The lowest temperature recorded in Uranus's tropopause is 49 K (−224 °C), making Uranus the coldest posed of ice in the conventional sense, but of a hot * * and dense fluid consisting of water, ammonia and other planet in the Solar System. [11] [65] volatiles.*[10]*[58] This fluid, which has a high electri- One of the hypotheses for this discrepancy suggests that cal conductivity, is sometimes called a water–ammonia when Uranus was hit by a supermassive impactor, which ocean.*[59] caused it to expel most of its primordial heat, it was left * According to research conducted at the University of with a depleted core temperature. [66] Another hypoth- California, Berkeley, the extreme pressure and temper- esis is that some form of barrier exists in Uranus's upper layers that prevents the core's heat from reaching the sur- ature deep within Uranus may break up the methane * molecules, with the carbon atoms condensing into crys- face. [10] For example, convection may take place in a set of compositionally different layers, which may inhibit tals of diamond that rain down through the mantle like * * * the upward heat transport; [11] [65] perhaps double dif- hailstones. [60] Very-high-pressure experiments at the * Lawrence Livermore National Laboratory suggest that fusive convection is a limiting factor. [10] the base of the mantle may comprise an ocean of liquid diamond, with floating solid 'diamond-bergs'.*[61]*[62] The bulk compositions of Uranus and Neptune are differ- 6.4 Atmosphere ent from those of Jupiter and Saturn, with ice dominating over gases, hence justifying their separate classification as Main article: Atmosphere of Uranus ice giants. There may be a layer of ionic water where the water molecules break down into a soup of hydrogen and Although there is no well-defined solid surface within oxygen ions, and deeper down superionic water in which Uranus's interior, the outermost part of Uranus's gaseous the oxygen crystallises but the hydrogen ions move freely envelope that is accessible to remote sensing is called * within the oxygen lattice. [63] its atmosphere.*[11] Remote-sensing capability extends Although the model considered above is reasonably stan- down to roughly 300 km below the 1 bar (100 kPa) level, dard, it is not unique; other models also satisfy observa- with a corresponding pressure around 100 bar (10 MPa) tions. For instance, if substantial amounts of hydrogen and temperature of 320 K.*[67] The tenuous of and rocky material are mixed in the ice mantle, the to- the atmosphere extends over two planetary radii from the tal mass of ices in the interior will be lower, and, corre- nominal surface, which is defined to lie at a pressure of spondingly, the total mass of rocks and hydrogen will be 1 bar.*[68] The Uranian atmosphere can be divided into higher. Presently available data does not allow science three layers: the troposphere, between altitudes of −300 to determine which model is correct.*[57] The fluid inte- and 50 km and pressures from 100 to 0.1 bar (10 MPa to rior structure of Uranus means that it has no solid surface. 10 kPa); the stratosphere, spanning altitudes between 50 The gaseous atmosphere gradually transitions into the in- and 4000 km and pressures of between 0.1 and 10*−10 ternal liquid layers.*[10] For the sake of convenience, a bar (10 kPa to 10 µPa); and the thermosphere/corona ex- revolving oblate spheroid set at the point at which atmo- tending from 4,000 km to as high as 50,000 km from the spheric pressure equals 1 bar (100 kPa) is conditionally surface.*[11] There is no mesosphere. designated as a “surface”. It has equatorial and polar radii of 25 559 ± 4 and 24 973 ± 20 km, respectively.*[8] This surface is used throughout this article as a zero point 6.4.1 Composition for altitudes. The composition of Uranus's atmosphere is different from its bulk, consisting mainly of molecular hydrogen and helium.*[11] The helium molar fraction, i.e. the 6.4. ATMOSPHERE 85 number of helium atoms per molecule of gas, is 0.15 ± 6.4.3 Upper atmosphere 0.03*[14] in the upper troposphere, which corresponds to a mass fraction 0.26 ± 0.05.*[11]*[65] This value is The middle layer of the Uranian atmosphere is the close to the protosolar helium mass fraction of 0.275 ± stratosphere, where temperature generally increases with 0.01,*[69] indicating that helium has not settled in its altitude from 53 K in the tropopause to between 800 centre as it has in the gas giants.*[11] The third-most- and 850 K at the base of the thermosphere.*[68] The abundant element in Uranus's atmosphere is methane heating of the stratosphere is caused by absorption * (CH4). [11] Methane has prominent absorption bands of solar UV and IR radiation by methane and other in the visible and near-infrared (IR), making Uranus hydrocarbons,*[78] which form in this part of the at- aquamarine or cyan in colour.*[11] Methane molecules mosphere as a result of methane photolysis.*[73] Heat account for 2.3% of the atmosphere by molar fraction is also conducted from the hot thermosphere.*[78] The below the methane cloud deck at the pressure level of 1.3 hydrocarbons occupy a relatively narrow layer at alti- bar (130 kPa); this represents about 20 to 30 times the tudes of between 100 and 300 km corresponding to a carbon abundance found in the Sun.*[11]*[13]*[70] The pressure range of 10 to 0.1 mbar (1000 to 10 kPa) and mixing ratio*[lower-alpha 7] is much lower in the upper temperatures of between 75 and 170 K.*[71]*[74] The atmosphere due to its extremely low temperature, which most abundant hydrocarbons are methane, acetylene and lowers the saturation level and causes excess methane to ethane with mixing ratios of around 10*−7 relative to hy- freeze out.*[71] The abundances of less volatile com- drogen. The mixing ratio of carbon monoxide is simi- pounds such as ammonia, water, and hydrogen sulfide lar at these altitudes.*[71]*[74]*[76] Heavier hydrocar- in the deep atmosphere are poorly known. They are bons and carbon dioxide have mixing ratios three orders probably also higher than solar values.*[11]*[72] Along of magnitude lower.*[74] The abundance ratio of wa- with methane, trace amounts of various hydrocarbons are ter is around 7×10*−9.*[75] Ethane and acetylene tend found in the stratosphere of Uranus, which are thought to condense in the colder lower part of stratosphere and to be produced from methane by photolysis induced tropopause (below 10 mBar level) forming haze lay- by the solar ultraviolet (UV) radiation.*[73] They in- ers,*[73] which may be partly responsible for the bland clude ethane (C2H6), acetylene (C2H2), methylacetylene appearance of Uranus. The concentration of hydrocar- * * * (CH3C2H), and diacetylene (C2HC2H). [71] [74] [75] bons in the Uranian stratosphere above the haze is signif- Spectroscopy has also uncovered traces of water vapor, icantly lower than in the stratospheres of the other giant carbon monoxide and carbon dioxide in the upper atmo- planets.*[71]*[79] sphere, which can only originate from an external source * * * The outermost layer of the Uranian atmosphere is the such as infalling dust and comets. [74] [75] [76] thermosphere and corona, which has a uniform tempera- ture around 800 to 850 K.*[11]*[79] The heat sources necessary to sustain such a high level are not under- stood, as neither the solar UV nor the auroral activ- 6.4.2 Troposphere ity can provide the necessary energy to maintain these temperatures. The weak cooling efficiency due to the lack of hydrocarbons in the stratosphere above 0.1 mBar The troposphere is the lowest and densest part of the at- pressure level may contribute too.*[68]*[79] In addition mosphere and is characterized by a decrease in tempera- to molecular hydrogen, the thermosphere-corona con- * ture with altitude. [11] The temperature falls from about tains many free hydrogen atoms. Their small mass and 320 K at the base of the nominal troposphere at −300 high temperatures explain why the corona extends as * * km to 53 K at 50 km. [67] [70] The temperatures in the far as 50 000 km, or two Uranian radii, from its sur- coldest upper region of the troposphere (the tropopause) face.*[68]*[79] This extended corona is a unique feature actually vary in the range between 49 and 57 K depending of Uranus.*[79] Its effects include a drag on small parti- * * on planetary latitude. [11] [64] The tropopause region is cles orbiting Uranus, causing a general depletion of dust responsible for the vast majority of Uranus's thermal far in the Uranian rings.*[68] The Uranian thermosphere, infrared emissions, thus determining its effective temper- together with the upper part of the stratosphere, corre- * * ature of 59.1 ± 0.3 K. [64] [65] sponds to the ionosphere of Uranus.*[70] Observations The troposphere is believed to possess a highly com- show that the ionosphere occupies altitudes from 2 000 plex cloud structure; water clouds are hypothesised to lie to 10 000 km.*[70] The Uranian ionosphere is denser in the pressure range of 50 to 100 bar (5 to 10 MPa), than that of either Saturn or Neptune, which may arise ammonium hydrosulfide clouds in the range of 20 to 40 from the low concentration of hydrocarbons in the strato- bar (2 to 4 MPa), ammonia or hydrogen sulfide clouds sphere.*[79]*[80] The ionosphere is mainly sustained by at between 3 and 10 bar (0.3 to 1 MPa) and finally di- solar UV radiation and its density depends on the solar ac- rectly detected thin methane clouds at 1 to 2 bar (0.1 to tivity.*[81] Auroral activity is insignificant as compared 0.2 MPa).*[11]*[13]*[67]*[77] The troposphere is a dy- to Jupiter and Saturn.*[79]*[82] namic part of the atmosphere, exhibiting strong winds, bright clouds and seasonal changes.*[17] • Uranus's atmosphere 86 CHAPTER 6. URANUS

• Temperature profile of the Uranian troposphere and is blue and the other one red.*[89]*[90] One hypothesis lower stratosphere. Cloud and haze layers are also concerning the outer ring's blue colour is that it is com- indicated. posed of minute particles of water ice from the surface of that are small enough to scatter blue light.*[89]*[91] • Zonal wind speeds on Uranus. Shaded areas show In contrast, Uranus's inner rings appear grey.*[89] the southern collar and its future northern counter- part. The red curve is a symmetrical fit to the data. • Uranus's rings • Animation about the discovering occultation in 6.5 Planetary rings 1977. (Click on it to start) • Uranus has a complicated planetary ring system, Main article: which was the second such system to be discovered in the Solar System after Saturn's.*[1] The rings are composed of extremely dark particles, • Uranus's aurorae against its equatorial rings, imaged which vary in size from micrometres to a fraction of a by the Hubble telescope. Unlike the aurorae of metre.*[16] Thirteen distinct rings are presently known, Earth and Jupiter, those of Uranus are not in line the brightest being the ε ring. All except two rings of with its poles, due to its lopsided magnetic field. Uranus are extremely narrow – they are usually a few kilo- metres wide. The rings are probably quite young; the dy- namics considerations indicate that they did not form with 1. ^ Cite error: The named reference Esposito2002 Uranus. The matter in the rings may once have been part was invoked but never defined (see the help page). of a moon (or moons) that was shattered by high-speed impacts. From numerous pieces of debris that formed as a result of those impacts, only a few particles survived, in 6.6 Magnetosphere stable zones corresponding to the locations of the present rings.*[83]*[84] William Herschel described a possible ring around Uranus in 1789. This sighting is generally considered doubtful, because the rings are quite faint, and in the two following centuries none were noted by other observers. Still, Herschel made an accurate description of the ep- silon ring's size, its angle relative to Earth, its red colour, and its apparent changes as Uranus travelled around the Sun.*[85]*[86] The ring system was definitively discov- ered on March 10, 1977 by James L. Elliot, Edward W. Dunham, and Jessica Mink using the Kuiper Airborne Observatory. The discovery was serendipitous; they planned to use the occultation of the star 158687 by Uranus to study its atmosphere. When their observations were analysed, they found that the star had disappeared The magnetic field of Uranus as observed by Voyager 2 in 1986. briefly from view five times both before and after it dis- S and N are magnetic south and north poles. appeared behind Uranus. They concluded that there must be a ring system around Uranus.*[87] Later they detected Before the arrival of Voyager 2, no measurements of the four additional rings.*[87] The rings were directly imaged Uranian magnetosphere had been taken, so its nature re- when Voyager 2 passed Uranus in 1986.*[16] Voyager 2 mained a mystery. Before 1986, astronomers had ex- also discovered two additional faint rings, bringing the pected the magnetic field of Uranus to be in line with total number to eleven.*[16] the solar wind, because it would then align with Uranus's * In December 2005, the Hubble Space Telescope detected poles that lie in the ecliptic. [92] a pair of previously unknown rings. The largest is located Voyager's observations revealed that Uranus's magnetic twice as far from Uranus as the previously known rings. field is peculiar, both because it does not originate from These new rings are so far from Uranus that they are its geometric centre, and because it is tilted at 59° from called the“outer”ring system. Hubble also spotted two the axis of rotation.*[92]*[93] In fact the magnetic dipole small satellites, one of which, Mab, shares its orbit with is shifted from the Uranus's center towards the south ro- the outermost newly discovered ring. The new rings bring tational pole by as much as one third of the planetary the total number of Uranian rings to 13.*[88] In April radius.*[92] This unusual geometry results in a highly 2006, images of the new rings from the Keck Observa- asymmetric magnetosphere, where the magnetic field tory yielded the colours of the outer rings: the outermost strength on the surface in the southern hemisphere can 6.7. CLIMATE 87

be as low as 0.1 gauss (10 µT), whereas in the northern hemisphere it can be as high as 1.1 gauss (110 µT).*[92] The average field at the surface is 0.23 gauss (23 µT).*[92] In comparison, the magnetic field of Earth is roughly as strong at either pole, and its“magnetic equator”is roughly parallel with its geographical equator.*[93] The dipole moment of Uranus is 50 times that of Earth.*[92]*[93] Neptune has a similarly displaced and tilted magnetic field, suggesting that this may be a common feature of ice giants.*[93] One hypothesis is that, unlike the magnetic fields of the terrestrial and gas giants, which are gener- Uranus's southern hemisphere in approximate natural colour ated within their cores, the ice giants' magnetic fields are (left) and in shorter wavelengths (right), showing its faint cloud generated by motion at relatively shallow depths, for in- bands and atmospheric “hood”as seen by Voyager 2 stance, in the water–ammonia ocean.*[59]*[94] Another possible explanation for the magnetosphere's alignment is that there are oceans of liquid diamond in Uranus's inte- tire planet.*[16]*[99] One proposed explanation for this rior that would deter the magnetic field.*[95] dearth of features is that Uranus's internal heat appears markedly lower than that of the other giant planets. The Despite its curious alignment, in other respects the Ura- lowest temperature recorded in Uranus's tropopause is 49 nian magnetosphere is like those of other planets: it K, making Uranus the coldest planet in the Solar System, has a bow shock at about 23 Uranian radii ahead of it, colder than Neptune.*[11]*[65] a magnetopause at 18 Uranian radii, a fully developed magnetotail, and radiation belts.*[92]*[93]*[96] Overall, the structure of Uranus's magnetosphere is different from Jupiter's and more similar to Saturn's.*[92]*[93] Uranus's 6.7.1 Banded structure, winds and clouds magnetotail trails behind it into space for millions of kilo- metres and is twisted by its sideways rotation into a long In 1986, Voyager 2 found that the visible southern hemi- corkscrew.*[92]*[97] sphere of Uranus can be subdivided into two regions: a bright polar cap and dark equatorial bands.*[16] Their Uranus's magnetosphere contains charged particles: boundary is located at about −45° of latitude. A nar- mainly protons and electrons, with a small amount of row band straddling the latitudinal range from −45 to * * * H2 + ions. [93] [96] No heavier ions have been de- −50° is the brightest large feature on its visible sur- tected. Many of these particles probably derive from face.*[16]*[100] It is called a southern “collar”. The * the hot atmospheric corona. [96] The ion and electron cap and collar are thought to be a dense region of methane energies can be as high as 4 and 1.2 megaelectronvolts, clouds located within the pressure range of 1.3 to 2 bar * respectively. [96] The density of low-energy (below 1 (see above).*[101] Besides the large-scale banded struc- kiloelectronvolt) ions in the inner magnetosphere is about ture, Voyager 2 observed ten small bright clouds, most * * 2 cm −3. [98] The particle population is strongly af- lying several degrees to the north from the collar.*[16] fected by the Uranian moons, which sweep through the In all other respects Uranus looked like a dynamically * magnetosphere, leaving noticeable gaps. [96] The par- dead planet in 1986. Voyager 2 arrived during the height ticle flux is high enough to cause darkening or space of Uranus's southern summer and could not observe the weathering of their surfaces on an astronomically rapid northern hemisphere. At the beginning of the 21st cen- * timescale of 100,000 years. [96] This may be the cause tury, when the northern polar region came into view, the of the uniformly dark colouration of the Uranian satel- Hubble Space Telescope (HST) and Keck telescope ini- * lites and rings. [84] Uranus has relatively well developed tially observed neither a collar nor a polar cap in the aurorae, which are seen as bright arcs around both mag- northern hemisphere.*[100] So Uranus appeared to be * netic poles. [79] Unlike Jupiter's, Uranus's aurorae seem asymmetric: bright near the south pole and uniformly to be insignificant for the energy balance of the planetary dark in the region north of the southern collar.*[100] * thermosphere. [82] In 2007, when Uranus passed its equinox, the south- ern collar almost disappeared, and a faint northern collar emerged near 45° of latitude.*[102] 6.7 Climate In the 1990s, the number of the observed bright cloud features grew considerably partly because new high- Main article: Climate of Uranus resolution imaging techniques became available.*[17] At ultraviolet and visible wavelengths, Uranus's atmo- Most were found in the northern hemisphere as it started sphere is bland in comparison to the other giant plan- to become visible.*[17] An early explanation—that bright ets, even to Neptune, which it otherwise closely resem- clouds are easier to identify in its dark part, whereas in bles.*[17] When Voyager 2 flew by Uranus in 1986, it the southern hemisphere the bright collar masks them observed a total of ten cloud features across the en- – was shown to be incorrect.*[103]*[104] Neverthe- 88 CHAPTER 6. URANUS

The first dark spot observed on Uranus. Image obtained by the HST ACS in 2006. less there are differences between the clouds of each hemisphere. The northern clouds are smaller, sharper and brighter.*[104] They appear to lie at a higher alti- tude.*[104] The lifetime of clouds spans several orders of magnitude. Some small clouds live for hours; at least one southern cloud may have persisted since the Voyager flyby.*[17]*[99] Recent observation also discovered that cloud features on Uranus have a lot in common with those on Neptune.*[17] For example, the dark spots common on Neptune had never been observed on Uranus before Uranus in 2005. Rings, southern collar and a bright cloud in the 2006, when the first such feature dubbed Uranus Dark northern hemisphere are visible (HST ACS image). Spot was imaged.*[105] The speculation is that Uranus is becoming more Neptune-like during its equinoctial sea- * son. [106] km/h) and a persistent thunderstorm referred to as The tracking of numerous cloud features allowed de- “Fourth of July fireworks”.*[99] On August 23, 2006, termination of zonal winds blowing in the upper tropo- researchers at the Space Science Institute (Boulder, Col- sphere of Uranus.*[17] At the equator winds are retro- orado) and the University of Wisconsin observed a dark grade, which means that they blow in the reverse direc- spot on Uranus's surface, giving astronomers more insight tion to the planetary rotation. Their speeds are from into Uranus's atmospheric activity.*[105] Why this sud- −100 to −50 m/s.*[17]*[100] Wind speeds increase with den upsurge in activity occurred is not fully known, but it the distance from the equator, reaching zero values near appears that Uranus's extreme axial tilt results in extreme ±20° latitude, where the troposphere's temperature mini- seasonal variations in its weather.*[51]*[106] Determin- mum is located.*[17]*[64] Closer to the poles, the winds ing the nature of this seasonal variation is difficult be- shift to a prograde direction, flowing with Uranus's rota- cause good data on Uranus's atmosphere have existed for tion. Wind speeds continue to increase reaching maxima less than 84 years, or one full Uranian year. at ±60° latitude before falling to zero at the poles.*[17] over the course of half a Uranian year (beginning in the Wind speeds at −40° latitude range from 150 to 200 m/s. 1950s) has shown regular variation in the brightness in Because the collar obscures all clouds below that parallel, two spectral bands, with maxima occurring at the sol- speeds between it and the southern pole are impossible stices and minima occurring at the equinoxes.*[109] A to measure.*[17] In contrast, in the northern hemisphere similar periodic variation, with maxima at the solstices, maximum speeds as high as 240 m/s are observed near has been noted in measurements of the deep +50° latitude.*[17]*[100]*[107] troposphere begun in the 1960s.*[110] Stratospheric temperature measurements beginning in the 1970s also showed maximum values near the 1986 solstice.*[78] 6.7.2 Seasonal variation The majority of this variability is believed to occur owing to changes in the viewing geometry.*[103] For a short period from March to May 2004, large There are some reasons to believe that physical seasonal clouds appeared in the Uranian atmosphere, giving it a changes are happening in Uranus. Although Uranus is Neptune-like appearance.*[104]*[108] Observations in- known to have a bright south polar region, the north pole cluded record-breaking wind speeds of 229 m/s (824 is fairly dim, which is incompatible with the model of 6.9. MOONS 89

the seasonal change outlined above.*[106] During its pre- larger they became; the larger they became, the more gas vious northern solstice in 1944, Uranus displayed ele- they held onto until a critical point was reached, and their vated levels of brightness, which suggests that the north size began to increase exponentially. The ice giants, with pole was not always so dim.*[109] This information im- only a few Earth masses of nebular gas, never reached plies that the visible pole brightens some time before the that critical point.*[112]*[113]*[114] Recent simulations solstice and darkens after the equinox.*[106] Detailed of have suggested that both ice giants analysis of the visible and microwave data revealed that formed closer to the Sun than their present positions, and the periodical changes of brightness are not completely moved outwards after formation (the Nice model).*[112] symmetrical around the solstices, which also indicates a change in the meridional albedo patterns.*[106] In the 1990s, as Uranus moved away from its solstice, Hub- 6.9 Moons ble and ground-based telescopes revealed that the south polar cap darkened noticeably (except the southern col- lar, which remained bright),*[101] whereas the northern Main article: hemisphere demonstrated increasing activity,*[99] such See also: Timeline of discovery of Solar System planets and their natural satellites as cloud formations and stronger winds, bolstering ex- * pectations that it should brighten soon.*[104] This indeed Uranus has 27 known natural satellites. [114] The names happened in 2007 when it passed an equinox: a faint northern polar collar arose, and the southern collar be- came nearly invisible, although the zonal wind profile re- mained slightly asymmetric, with northern winds being somewhat slower than southern.*[102] The mechanism of these physical changes is still not clear.*[106] Near the summer and winter solstices, Uranus's hemispheres lie alternately either in full glare of Major moons of Uranus in order of increasing distance (left to right), at their proper relative sizes and (collage of Voy- the Sun's rays or facing deep space. The brightening of ager 2 photographs) the sunlit hemisphere is thought to result from the local thickening of the methane clouds and haze layers located in the troposphere.*[101] The bright collar at −45° lati- tude is also connected with methane clouds.*[101] Other changes in the southern polar region can be explained by changes in the lower cloud layers.*[101] The varia- tion of the microwave emission from Uranus is probably caused by changes in the deep tropospheric circulation, because thick polar clouds and haze may inhibit convec- tion.*[111] Now that the spring and autumn equinoxes are arriving on Uranus, the dynamics are changing and convection can occur again.*[99]*[111]

6.8 Formation

Main article: Formation and evolution of the Solar System For details of the evolution of Uranus's orbit, see Nice model. The Uranus System (NACO/VLT image) Many argue that the differences between the ice giants and the gas giants extend to their formation.*[112]*[113] of these satellites are chosen from characters in the works The Solar System is believed to have formed from a gi- of and Alexander Pope.*[58]*[115] The five ant rotating ball of gas and dust known as the presolar main satellites are , , , Titania, and nebula. Much of the nebula's gas, primarily hydrogen Oberon.*[58] The Uranian satellite system is the least and helium, formed the Sun, and the dust grains col- massive among those of the giant planets; the combined lected together to form the first . As the mass of the five major satellites would be less than half planets grew, some of them eventually accreted enough that of Triton (largest moon of Neptune) alone.*[9] The matter for their gravity to hold on to the nebula's left- largest of Uranus's satellites, Titania, has a radius of only over gas.*[112]*[113] The more gas they held onto, the 788.9 km, or less than half that of the Moon, but slightly 90 CHAPTER 6. URANUS

more than Rhea, the second-largest satellite of Saturn, making Titania the eighth-largest moon in the Solar Sys- In 1986, NASA's Voyager 2 interplanetary probe encoun- tem. Uranus's satellites have relatively low albedos; rang- tered Uranus. This flyby remains the only investigation ing from 0.20 for Umbriel to 0.35 for Ariel (in green * of Uranus carried out from a short distance and no other light). [16] They are ice–rock conglomerates composed visits are planned. Launched in 1977, Voyager 2 made its of roughly 50% ice and 50% rock. The ice may include * * closest approach to Uranus on January 24, 1986, coming ammonia and carbon dioxide. [84] [116] within 81,500 kilometres of the cloudtops, before con- Among the Uranian satellites, Ariel appears to have tinuing its journey to Neptune. Voyager 2 studied the the youngest surface with the fewest impact craters structure and chemical composition of Uranus's atmo- and Umbriel's the oldest.*[16]*[84] Miranda possesses sphere,*[70] including its unique weather, caused by its fault canyons 20 kilometres deep, terraced layers, and a axial tilt of 97.77°. It made the first detailed investi- chaotic variation in surface ages and features.*[16] Mi- gations of its five largest moons and discovered 10 new randa's past geologic activity is believed to have been ones. It examined all nine of the system's known rings driven by at a time when its orbit was more and discovered two more.*[16]*[84]*[123] It also stud- eccentric than currently, probably as a result of a former ied the magnetic field, its irregular structure, its tilt and 3:1 orbital resonance with Umbriel.*[117] Extensional its unique corkscrew magnetotail caused by Uranus's side- processes associated with upwelling diapirs are the likely ways orientation.*[92] * * origin of Miranda's 'racetrack'-like coronae. [118] [119] The possibility of sending the Cassini spacecraft from Ariel is believed to have once been held in a 4:1 resonance * Saturn to Uranus was evaluated during a mission exten- with Titania. [120] sion planning phase in 2009.*[124] It would take about Uranus possesses at least one horseshoe orbiter occu- twenty years to get to the Uranian system after depart- * pying the Sun–Uranus L3 Lagrangian point —a grav- ing Saturn. [124] A Uranus orbiter and probe was rec- itationally unstable region at 180º in its orbit, 83982 ommended by the 2013–2022 Planetary Science Decadal Crantor.*[121]*[122] Crantor moves inside Uranus's co- Survey published in 2011; the proposal envisages launch orbital region on a complex, temporary . during 2020–2023 and a 13-year cruise to Uranus.*[125] 2010 EU65 is also a promising Uranus horseshoe librator A Uranus entry probe could use Pioneer Venus Multi- candidate.*[122] probe heritage and descend to 1–5 atmospheres.*[125] The ESA evaluated a “medium-class”mission called Uranus Pathfinder.*[126] A New Frontiers Uranus Or- 6.10 Exploration biter has been evaluated and recommended in the study, The Case for a Uranus Orbiter.*[127] Such a mission is aided by the ease with which a relatively big mass can be sent to the system—over 1500 kg with an Atlas 521 and 12-year journey.*[128] For more concepts see Proposed Uranus missions.

6.11 In culture

In astrology, the planet Uranus ( ) is the ruling planet of Aquarius. Because Uranus is cyan and Uranus is asso- ciated with electricity, the colour electric blue, which is close to cyan, is associated with the sign Aquarius*[129] (see Uranus in astrology). The chemical element uranium, discovered in 1789 by the German chemist Martin Heinrich Klaproth, was named after the newly discovered planet Uranus.*[130] “Uranus, the Magician" is a movement in Gustav Holst's The Planets, written between 1914 and 1916. Operation Uranus was the successful military operation in World War II by the Soviet army to take back Stalingrad and marked the turning point in the land war against the Crescent Uranus as imaged by Voyager 2 while en route to Nep- Wehrmacht. tune The lines “Then felt I like some watcher of the Main article: Exploration of Uranus skies/When a new planet swims into his ken”, from John 6.14. REFERENCES 91

Keats's "On First Looking Into 's Homer", are [4] Because, in the English-speaking world, the latter sounds a reference to Herschel's discovery of Uranus.*[131] like“your anus", the former pronunciation also saves em- barrassment: as Pamela Gay, an astronomer at Southern Illinois University Edwardsville, noted on her podcast, to avoid “being made fun of by any small schoolchildren 6.12 See also ... when in doubt, don't emphasise anything and just say /ˈjʊərənəs/. And then run, quickly.”*[40] • 2011 QF99, the only known Uranus trojan • Colonization of Uranus [5] Cf. (not supported by all fonts) • Uranus in astrology [6] Cf. (not supported by all fonts) • Uranus in fiction [7] Mixing ratio is defined as the number of molecules of a compound per a molecule of hydrogen. 6.13 Notes

[1] Orbital elements refer to the Uranus barycentre and Solar 6.14 References System Barycentre. They are the instantaneous osculating values at the precise J2000 epoch. Barycentre quantities [1]“Uranus”. Oxford English Dictionary (2 ed.). 1989. are given because, in contrast to the planetary centre, they do not experience appreciable changes on a day-to-day ba- [2] The BBC Pronunciation Unit notes that /ˈjʊərənəs/“is the sis from the motion of the moons. preferred usage of astronomers": Olausson, Lena; Sang- ster, Catherine (2006). The Oxford BBC Guide to Pro- [2] Refers to the level of 1 bar atmospheric pressure. nunciation. Oxford, England: Oxford University Press. [3] Calculated using data from Seidelmann, 2007.*[8] omi- p. 404. ISBN 978-0-19-280710-6. calCircumference 159354.1 km*[4] Surface area [3] Yeomans, Donald K. “HORIZONS Web-Interface for 8.1156×109 km2*[4]*[lower-alpha 2] Uranus Barycenter (Major Body=7)". JPL Horizons On- 15.91 EarthsVolume 6.833×1013 km3*[6]*[lower-alpha Line Ephemeris System. Retrieved July 18, 2014. — 2] Select “Ephemeris Type: Orbital Elements”, “Time 63.086 EarthsMass (8.6810±0.0013)×1025 kg Span: 2000-01-01 12:00 to 2000-01-02”.(“Target Body: 14.536 Earths*[9] Uranus Barycenter”and“Center: Solar System Barycen- GM=5793939±13 km3/s2 ter (@0)".) Mean density 1.27 g/cm3*[6]*[lower-alpha 2] [4] Munsell, Kirk (May 14, 2007). “NASA: Solar System Surface gravity Exploration: Planets: Uranus: Facts & Figures”. NASA. 8.69 m/s2*[6]*[lower-alpha 2] Retrieved August 13, 2007. 0.886 g [5] Seligman, Courtney. “Rotation Period and Day Length” . Retrieved August 13, 2009. 21.3 km/s*[6]*[lower-alpha 2] Sidereal rotation period [6] Williams, Dr. David R. (January 31, 2005). “Uranus 0.71833 d (Retrograde) Fact Sheet”. NASA. Retrieved August 10, 2007. 17 h 14 min 24 s*[8] Equatorial rotation velocity [7] “The MeanPlane (Invariable plane) of the Solar System 2.59 km/s passing through the barycenter”. April 3, 2009. Retrieved 9,320 km/h April 10, 2009. (produced with Solex 10 written by Aldo Axial tilt Vitagliano; see also Invariable plane) 97.77°*[8] North pole [8] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, 17*h 9*m 15*s Michael F. et al. (2007). “Report of the IAU/IAG 257.311°*[8] Working Group on cartographic coordinates and North pole rotational elements: 2006”. Celestial Mechan- −15.175°*[8]Albedo 0.300 (Bond) ics and Dynamical Astronomy 98 (3): 155–180. 0.51 (geom.)*[6] Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- Apparent magnitude 007-9072-y. 5.9*[12] to 5.32*[6] Angular diameter [9] Jacobson, R. A.; , J. K.; Taylor, A. H.; Syn- 3.3″ to 4.1″*[6]Atmosphere*[11]*[13]*[14]covered ele- nott, S. P. (June 1992). “The masses of Uranus and ment [[uranium Calculation of He, H2 and CH4 molar its major satellites from Voyager tracking data and earth- fractions is based on a 2.3% mixing ratio of methane to based Uranian satellite data”. The Astronomical Jour- hydrogen and the 15/85 He/H2 proportions measured at nal 103 (6): 2068–2078. Bibcode:1992AJ....103.2068J. the tropopause. doi:10.1086/116211. 92 CHAPTER 6. URANUS

[10] Podolak, M.; Weizman, A.; Marley, M. (December London 71: 492–501. Bibcode:1781RSPT...71..492H. 1995). “Comparative models of Uranus and Neptune” doi:10.1098/rstl.1781.0056. . Planetary and Space Science 43 (12): 1517–1522. Bibcode:1995P&SS...43.1517P. doi:10.1016/0032- [23] Journal of the Royal Society and Royal Astronomical So- 0633(95)00061-5. ciety 1, 30, quoted in Miner, p. 8

[11] Lunine, Jonathan I. (September 1993). “The [24] Royal Astronomical Society MSS W.2/1.2, 23; quoted in Atmospheres of Uranus and Neptune”. An- Miner p. 8 nual Review of Astronomy and Astrophysics 31: [25] RAS MSS Herschel W.2/1.2, 24, quoted in Miner p. 8 217–263. Bibcode:1993ARA&A..31..217L. doi:10.1146/annurev.aa.31.090193.001245. [26] Journal of the Royal Society and Royal Astronomical So- ciety 1, 30; quoted in Miner p. 8 [12] Espenak, Fred (2005). “Twelve Year Planetary Ephemeris: 1995–2006”. NASA. Archived from the orig- [27] RAS MSS Herschel W1/13.M, 14 quoted in Miner p. 8 inal on 2007-06-26. Retrieved June 14, 2007. [28] Lexell, A. J. (1783).“Recherches sur la nouvelle planete, [13] Lindal, G. F.; Lyons, J. R.; Sweetnam, D. N.; Eshle- decouverte par M. Herschel & nominee Georgium Sidus” man, V. R.; Hinson, D. P.; Tyler, G. L. (December 30, . Acta Academia Scientarum Imperialis Petropolitanae (1): 1987). “The Atmosphere of Uranus: Results of Radio 303–329. Occultation Measurements with Voyager 2”. Journal of Geophysical Research (American Geophysical Union) 92 [29] , Berliner Astronomisches Jahrbuch, p. (A13): 14,987–15,001. Bibcode:1987JGR....9214987L. 210, 1781, quoted in Miner, p. 11 doi:10.1029/JA092iA13p14987. ISSN 0148-0227. [30] Miner, p. 11 [14] Conrath, B.; Gautier, D.; Hanel, R.; Lindal, G.; Marten, A. (1987).“The Helium Abundance of Uranus from Voy- [31] , J. L. E., (1912). The Scientific Papers of Sir ager Measurements”. Journal of Geophysical Research 92 William Herschel 1. Royal Society and Royal Astronomi- (A13): 15003–15010. Bibcode:1987JGR....9215003C. cal Society. p. 100. ISBN 1-84371-022-6. doi:10.1029/JA092iA13p15003. [32] Miner, p. 12 [15] Feuchtgruber, H.; Lellouch, E.; Bézard, B.; Encrenaz, [33] RAS MSS Herschel W.1/12.M, 20, quoted in Miner, p. Th.; de Graauw, Th.; Davis, G. R. (1999). “Detection 12 of HD in the atmospheres of Uranus and Neptune: a new determination of the D/H ratio”. Astronomy and Astro- [34] “Voyager at Uranus”. Nasa Jpl 7 (85): 400–268. 1986. physics 341: L17–L21. Bibcode:1999A&A...341L..17F. Archived from the original on February 10, 2006.

[16] Smith, B. A.; Soderblom, L. A.; Beebe, A.; , [35] Herschel, Francisca (1917). “The meaning of the sym- D.; Boyce, J. M.; Brahic, A.; Briggs, G. A.; Brown, bol H+o for the planet Uranus”. The Observatory (The R. H.; , S. A. (4 July 1986). “Voyager 2 in Observatory) 40: 306. Bibcode:1917Obs....40..306H. the Uranian System: Imaging Science Results”. Sci- ence 233 (4759): 43–64. Bibcode:1986Sci...233...43S. [36] Littmann, Mark (2004). Planets Beyond: Discovering the doi:10.1126/science.233.4759.43. PMID 17812889. Outer Solar System. Courier Dover Publications. pp. 10– 11. ISBN 0-486-43602-0. [17] Sromovsky, L. A.; Fry, P. M. (December 2005). “Dynamics of cloud features on Uranus”. Icarus [37] Daugherty, Brian.“Astronomy in Berlin”. Brian Daugh- 179 (2): 459–484. Bibcode:2005Icar..179..459S. erty. Retrieved May 24, 2007. doi:10.1016/j.icarus.2005.07.022. [38] Finch, James (2006). “The Straight Scoop on Uranium” [18] “MIRA's Field Trips to the Stars Internet Education Pro- . allchemicals.info: The online chemical resource. Re- gram”. Monterey Institute for Research in Astronomy. Re- trieved March 30, 2009. trieved August 27, 2007. [39]“Uranian, a.2 and n.1". Oxford English Dictionary (2 ed.). [19] René Bourtembourg (2013). “Was Uranus Observed by 1989. Hipparchos?". Journal for the History of Astronomy 44: 377–387. doi:10.1177/002182861304400401. [40] Cain, Frasier (November 12, 2007). “Astronomy Cast: Uranus”. Retrieved April 20, 2009. [20] Dunkerson, Duane. “Uranus – About Saying, Finding, and Describing It”. thespaceguy.com. Retrieved April [41] “Planet symbols”. NASA Solar System exploration. Re- 17, 2007. trieved August 4, 2007.

[21] “Bath Preservation Trust”. Retrieved September 29, [42] ‹The template Chinaplanetnames is being considered for 2007. deletion.› China: De Groot, Jan Jakob Maria (1912). Religion in [22] Herschel, William; Watson, Dr. (1781). “Account China: universism. a key to the study of Taoism and Con- of a Comet, By Mr. Herschel, F. R. S.; Commu- fucianism. American lectures on the history of religions 10 nicated by Dr. Watson, Jun. of Bath, F. R. S” (G. P. Putnam's Sons). p. 300. Retrieved 2010-01-08. . Philosophical Transactions of the Royal Society of Japan: Crump, Thomas (1992). The Japanese numbers 6.14. REFERENCES 93

game: the use and understanding of numbers in modern [59] Atreya, S.; Egeler, P.; Baines, K. (2006). “Water- Japan. Nissan Institute/Routledge Japanese studies series ammonia ionic ocean on Uranus and Neptune?" (PDF). (Routledge). pp. 39–40. ISBN 0415056098. Geophysical Research Abstracts 8: 05179. Korea: Hulbert, Homer Bezaleel (1909). The passing of Korea. Doubleday, Page & company. p. 426. Retrieved [60] “Is It Raining Diamonds On Uranus”. SpaceDaily.com. 2010-01-08. October 1, 1999. Retrieved May 17, 2013.

[43] “Asian Astronomy 101”. Hamilton Amateur Astronomers [61] Bland, Eric (January 15, 2010). “Diamond Oceans Pos- 4 (11). 1997. Retrieved August 5, 2007. sible on Uranus, Neptune”. Discovery.com. Retrieved May 17, 2013. [44] Jean Meeus, Astronomical Algorithms (Richmond, VA: Willmann-Bell, 1998) p 271. From the 1841 aphelion [62] Baldwin, Emily (January 21, 2010).“Oceans of diamond to the 2092 one, perihelia are always 18.28 and aphelia possible on Uranus and Neptune”. astronomynow.com. always 20.10 astronomical units Retrieved February 6, 2014.

[45] “Next Stop Uranus”. 1986. Retrieved June 9, 2007. [63] Weird water lurking inside giant planets, New Scien- tist,September 1, 2010, Magazine issue 2776. [46] Forbes, George (1909). “History of Astronomy”. Re- trieved August 7, 2007. [64] Hanel, R.; Conrath, B.; Flasar, F. M.; Kunde, V.; Maguire, W.; Pearl, J.; Pirraglia, J.; Samuel- [47] O'Connor, J J. and Robertson, E. F. (1996).“Mathemat- son, R.; Cruikshank, D. (4 July 1986). “In- ical discovery of planets”. Retrieved June 13, 2007. frared Observations of the Uranian System”. Sci- ence 233 (4759): 70–74. Bibcode:1986Sci...233...70H. [48] Gierasch, Peter J. and Nicholson, Philip D. (2004). doi:10.1126/science.233.4759.70. PMID 17812891. “Uranus”. World Book. Retrieved March 8, 2015. [65] Pearl, J. C.; Conrath, B. J.; Hanel, R. A.; Pirraglia, J. [49] Sromovsky, Lawrence (2006). “Hubble captures rare, A.; Coustenis, A. (March 1990). “The albedo, ef- fleeting shadow on Uranus”. University of Wisconsin fective temperature, and energy balance of Uranus, as Madison. Retrieved June 9, 2007. determined from Voyager IRIS data”. Icarus 84 (1): 12–28. Bibcode:1990Icar...84...12P. doi:10.1016/0019- [50] Hammel, Heidi B. (September 5, 2006). “Uranus nears 1035(90)90155-3. ISSN 0019-1035. Equinox”(PDF). A report from the 2006 Pasadena Work- shop. Archived from the original on 2009-02-25. [66] Hawksett, David (2005). “Ten Mysteries of the Solar System: Why is Uranus So Cold?". Astronomy Now: 73. [51] “Hubble Discovers Dark Cloud In The Atmosphere Of Uranus”. Science Daily. Retrieved April 16, 2007. [67] de Pater, Imke; Romani, Paul N.; Atreya, Sushil K. (June 1991). “Possible microwave absorption by H S [52] Bergstralh, Jay T.; Miner, Ellis; Matthews, Mildred 2 gas in Uranus' and Neptune's atmospheres” (PDF). (1991). Uranus. pp. 485–486. ISBN 0-8165-1208-6. Icarus 91 (2): 220–233. Bibcode:1991Icar...91..220D. [53] “Report of the IAU/IAG working group on cartographic doi:10.1016/0019-1035(91)90020-T. ISSN 0019-1035. coordinates and rotational elements of the planets and [68] Herbert, F.; Sandel, B. R.; Yelle, R. V.; Holberg, J. B.; satellites: 2000”. IAU. 2000. Retrieved June 13, 2007. Broadfoot, A. L.; Shemansky, D. E.; Atreya, S. K.; Ro- [54] “Cartographic Standards”(PDF). NASA. Retrieved June mani, P. N. (December 30, 1987). “The Upper At- 13, 2007. mosphere of Uranus: EUV Occultations Observed by Voyager 2” (PDF). Journal of Geophysical Research 92 [55] “Coordinate Frames Used in MASL”. 2003. Archived (A13): 15,093–15,109. Bibcode:1987JGR....9215093H. from the original on May 5, 2007. Retrieved June 13, doi:10.1029/JA092iA13p15093. 2007. [69] Lodders, Katharina (July 10, 2003). “Solar Sys- [56] Nowak, Gary T. (2006). “Uranus: the Threshold Planet tem Abundances and Condensation Temperatures of of 2006”. Archived from the original on 2011-07-27. the Elements” (PDF). The Astrophysical Journal (The Retrieved June 14, 2007. American Astronomical Society) 591 (2): 1220–1247. Bibcode:2003ApJ...591.1220L. doi:10.1086/375492. [57] Podolak, M.; Podolak, J. I.; Marley, M. S. (Febru- ary 2000). “Further investigations of random mod- [70] Tyler, J.L.; Sweetnam, D.N.; Anderson, J.D.; Camp- els of Uranus and Neptune”. Planetary and Space Sci- bell, J. K.; Eshleman, V. R.; Hinson, D. P.; Levy, ence 48 (2–3): 143–151. Bibcode:2000P&SS...48..143P. G. S.; Lindal, G. F.; Marouf, E. A.; Simpson, R. A. doi:10.1016/S0032-0633(99)00088-4. (1986). “Voyger 2 Radio Science Observations of the Uranian System: Atmosphere, Rings, and Satellites”. Sci- [58] Faure, Gunter; Mensing, Teresa (2007). “Uranus: ence 233 (4759): 79–84. Bibcode:1986Sci...233...79T. What Happened Here?". In Faure, Gunter; Mensing, doi:10.1126/science.233.4759.79. PMID 17812893. Teresa M. Introduction to Planetary Science. Introduc- tion to Planetary Science. Springer Netherlands. p. 369. [71] Bishop, J.; Atreya, S. K.; Herbert, F.; Romani, P. (De- doi:10.1007/978-1-4020-5544-7_18. ISBN 978-1-4020- cember 1990). “Reanalysis of voyager 2 UVS oc- 5233-0. cultations at Uranus: Hydrocarbon mixing ratios in the 94 CHAPTER 6. URANUS

equatorial stratosphere” (PDF). Icarus 88 (2): 448– [82] Lam, H. A.; Miller, S.; Joseph, R. D.; Geballe, 464. Bibcode:1990Icar...88..448B. doi:10.1016/0019- T. R.; Trafton, L. M.; Tennyson, J.; Ballester, G. * 1035(90)90094-P. E. (1997-01-01). “Variation in the H3 + Emission of Uranus” (PDF). The Astrophysical Journal (The [72] de Pater, I.; Romani, P. N.; Atreya, S. K. (December American Astronomical Society) 474 (1): L73–L76. 1989). “Uranius Deep Atmosphere Revealed” (PDF). Bibcode:1997ApJ...474L..73L. doi:10.1086/310424. Icarus 82 (2): 288–313. Bibcode:1989Icar...82..288D. doi:10.1016/0019-1035(89)90040-7. ISSN 0019-1035. [83] Esposito, L.W. (2002). “Planetary rings”. Re- ports on Progress in Physics 65 (12): 1741–1783. [73] Summers, M. E.; Strobel, D. F. (November 1, Bibcode:2002RPPh...65.1741E. doi:10.1088/0034- 1989). “Photochemistry of the atmosphere of 4885/65/12/201. ISBN 0-521-36222-9. Uranus”. The Astrophysical Journal 346: 495–508. Bibcode:1989ApJ...346..495S. doi:10.1086/168031. [84] “Voyager Uranus Science Summary”. NASA/JPL. 1988. ISSN 0004-637X. Retrieved June 9, 2007.

[74] Burgdorf, M.; Orton, G.; Vancleve, J.; Meadows, V.; [85] “Uranus rings 'were seen in 1700s'". BBC News. April Houck, J. (October 2006). “Detection of new hydrocar- 19, 2007. Retrieved April 19, 2007. bons in Uranus' atmosphere by infrared spectroscopy”. Icarus 184 (2): 634–637. Bibcode:2006Icar..184..634B. [86] “Did William Herschel Discover The Rings Of Uranus In doi:10.1016/j.icarus.2006.06.006. The 18th Century?". Physorg.com. 2007. Retrieved June 20, 2007. [75] Encrenaz, Thérèse (February 2003). “ISO obser- “ vations of the giant planets and Titan: what have we [87] Elliot, J. L.; Dunham, E.; Mink, D. (1977). The rings ” learnt?". Planetary and Space Science 51 (2): 89–103. of Uranus . Cornell University. Retrieved June 9, 2007. Bibcode:2003P&SS...51...89E. doi:10.1016/S0032- [88] “NASA's Hubble Discovers New Rings and Moons 0633(02)00145-9. Around Uranus”. Hubblesite. 2005. Retrieved June 9, 2007. [76] Encrenaz, T.; Lellouch, E.; Drossart, P.; Feuchtgruber, H.; Orton, G. S.; Atreya, S. K. (January 2004). “First [89] dePater, Imke; Hammel, Heidi B.; Gibbard, Seran detection of CO in Uranus”(PDF). Astronomy and Astro- G.; Showalter Mark R. (2006). “New Dust Belts physics 413 (2): L5–L9. Bibcode:2004A&A...413L...5E. of Uranus: Two Ring, red Ring, Blue Ring”. Sci- doi:10.1051/0004-6361:20034637. ence 312 (5770): 92–94. Bibcode:2006Sci...312...92D. doi:10.1126/science.1125110. PMID 16601188. [77] Atreya, Sushil K.; Wong, Ah-San (2005). “Cou- — pled Clouds and Chemistry of the Giant Planets [90] Sanders, Robert (April 6, 2006). “Blue ring discovered ” A Case for Multiprobes (PDF). Space Science Re- around Uranus”. UC Berkeley News. Retrieved October views 116: 121–136. Bibcode:2005SSRv..116..121A. 3, 2006. doi:10.1007/s11214-005-1951-5. ISSN 0032-0633. [91] Battersby, Stephen (April 2006). “Blue ring of Uranus [78] Young, Leslie A.; Bosh, Amanda S.; Buie, Marc; linked to sparkling ice”. New Scientist. Retrieved June 9, Elliot, J. L.; Wasserman, Lawrence H. (2001). 2007. “Uranus after Solstice: Results from the 1998 November 6 Occultation” (PDF). Icarus 153 [92] Ness, Norman F.; Acuña, Mario H.; Behannon, Ken- (2): 236–247. Bibcode:2001Icar..153..236Y. neth W.; Burlaga, Leonard F.; Connerney, John E. doi:10.1006/icar.2001.6698. P.; Lepping, Ronald P.; Neubauer, Fritz M. (July 1986). “Magnetic Fields at Uranus”. Science [79] Herbert, Floyd; Sandel, Bill R. (August–September 233 (4759): 85–89. Bibcode:1986Sci...233...85N. 1999). “Ultraviolet observations of Uranus and doi:10.1126/science.233.4759.85. PMID 17812894. Neptune”. Planetary and Space Science 47 (8– 9): 1,119–1,139. Bibcode:1999P&SS...47.1119H. [93] Russell, C.T. (1993). “Planetary Magneto- doi:10.1016/S0032-0633(98)00142-1. spheres”. Rep. Prog. Phys. 56 (6): 687–732. Bibcode:1993RPPh...56..687R. doi:10.1088/0034- [80] Trafton, L. M.; Miller, S.; Geballe, T. R.; Ten- 4885/56/6/001. nyson, J.; Ballester, G. E. (October 1999). “H2 * Quadrupole and H3 + Emission from Uranus: The [94] Stanley, Sabine; Bloxham, Jeremy (2004). “Convective- Uranian Thermosphere, Ionosphere, and Aurora”. region geometry as the cause of Uranus' and Nep- The Astrophysical Journal 524 (2): 1,059–1,083. tune's unusual magnetic fields” (PDF). Letters to Nature Bibcode:1999ApJ...524.1059T. doi:10.1086/307838. 428 (6979): 151–153. Bibcode:2004Natur.428..151S. doi:10.1038/nature02376. PMID 15014493. Archived [81] Encrenaz, T.; Drossart, P.; Orton, G.; Feuchtgruber, from the original on August 7, 2007. Retrieved August 5, H.; Lellouch, E.; Atreya, S. K. (December 2003). 2007. * “The rotational temperature and column density of H3 + in Uranus” (PDF). Planetary and Space Science 51 [95] Bland, Eric (Jan 15, 2010). “Diamond Oceans Possible (14–15): 1013–1016. Bibcode:2003P&SS...51.1013E. on Uranus, Neptune”. Discovery.com. Retrieved May doi:10.1016/j.pss.2003.05.010. 17, 2013. 6.14. REFERENCES 95

[96] Krimigis, S. M.; , T. P.; Axford, W. [107] Hammel, H. B.; Rages, K.; Lockwood, G. W.; I.; Cheng, A. F.; Gloeckler, G.; Hamilton, D. Karkoschka, E.; de Pater, I. (October 2001). “New C.; Keath, E. P.; Lanzerotti, L. J.; Mauk, B. H. Measurements of the Winds of Uranus”. Icarus (4 July 1986). “The Magnetosphere of Uranus: 153 (2): 229–235. Bibcode:2001Icar..153..229H. Hot Plasma and Radiation Environment”. Science doi:10.1006/icar.2001.6689. 233 (4759): 97–102. Bibcode:1986Sci...233...97K. doi:10.1126/science.233.4759.97. PMID 17812897. [108] Devitt, Terry (2004). “Keck zooms in on the weird weather of Uranus”. University of Wisconsin-Madison. [97] “Voyager: Uranus: Magnetosphere”. NASA. 2003. Re- Retrieved December 24, 2006. trieved June 13, 2007. [109] Lockwood, G. W.; Jerzykiewicz, M. A. A. [98] Bridge, H.S.; Belcher, J.W.; Coppi, B.; Lazarus, A. (February 2006). “Photometric variability of J.; McNutt Jr, R. L.; Olbert, S.; Richardson, J. D.; Uranus and Neptune, 1950–2004”. Icarus 180 Sands, M. R.; Selesnick, R. S.; Sullivan, J. D.; Har- (2): 442–452. Bibcode:2006Icar..180..442L. tle, R. E.; Ogilvie, K. W.; Sittler Jr, E. C.; Bagenal, doi:10.1016/j.icarus.2005.09.009. F.; Wolff, R. S.; Vasyliunas, V. M.; Siscoe, G. L.; Go- ertz, C. K.; Eviatar, A. (1986). “Plasma Observations [110] Klein, M. J.; Hofstadter, M. D. (September 2006). “ Near Uranus: Initial Results from Voyager 2”. Sci- Long-term variations in the microwave brightness ” ence 233 (4759): 89–93. Bibcode:1986Sci...233...89B. temperature of the Uranus atmosphere . Icarus doi:10.1126/science.233.4759.89. PMID 17812895. 184 (1): 170–180. Bibcode:2006Icar..184..170K. doi:10.1016/j.icarus.2006.04.012. [99] Lakdawalla, Emily (2004). “No Longer Boring: 'Fire- [111] Hofstadter, M. D.; Butler, B. J. (September 2003). works' and Other Surprises at Uranus Spotted Through “Seasonal change in the deep atmosphere of Uranus”. Adaptive Optics”. The Planetary Society. Archived from Icarus 165 (1): 168–180. Bibcode:2003Icar..165..168H. the original on 2012-02-12. Retrieved June 13, 2007. doi:10.1016/S0019-1035(03)00174-X. [100] Hammel, H. B.; De Pater, I.; Gibbard, S. G.; Lockwood, [112] Thommes, Edward W.; Duncan, Martin J.; Levi- G. W.; Rages, K. (June 2005). “Uranus in 2003: Zonal son, Harold F. (1999). “The formation of Uranus winds, banded structure, and discrete features” (PDF). and Neptune in the Jupiter-Saturn region of the So- Icarus 175 (2): 534–545. Bibcode:2005Icar..175..534H. lar System” (PDF). Nature 402 (6762): 635–638. doi:10.1016/j.icarus.2004.11.012. Bibcode:1999Natur.402..635T. doi:10.1038/45185. [101] Rages, K. A.; Hammel, H. B.; Friedson, A. J. PMID 10604469. “ (11 September 2004). Evidence for tempo- [113] Brunini, Adrian; Fernandez, Julio A. (1999). “Nu- ” ral change at Uranus' south pole . Icarus 172 merical simulations of the accretion of Uranus and (2): 548–554. Bibcode:2004Icar..172..548R. Neptune”. Plan. Space Sci. 47 (5): 591–605. doi:10.1016/j.icarus.2004.07.009. Bibcode:1999P&SS...47..591B. doi:10.1016/S0032- 0633(98)00140-8. [102] Sromovsky, L. A.; Fry, P. M.; Hammel, H. B.; Ahue, W. M.; de Pater, I.; Rages, K. A.; Showal- [114] Sheppard, S. S.; Jewitt, D.; Kleyna, J. (2005). “An Ul- ter, M. R.; van Dam, M. A. (September 2009). tradeep Survey for Irregular Satellites of Uranus: Limits “Uranus at equinox: Cloud morphology and dynamics”. to Completeness”. The Astronomical Journal 129: 518. Icarus 203 (1): 265–286. Bibcode:2009Icar..203..265S. doi:10.1086/426329. doi:10.1016/j.icarus.2009.04.015. [115] “Uranus”. nineplanets.org. Retrieved July 3, 2007. [103] Karkoschka, Erich (May 2001). “Uranus' Ap- parent Seasonal Variability in 25 HST Filters”. [116] Hussmann, Hauke; Sohl, Frank; Spohn, Tilman (2006). Icarus 151 (1): 84–92. Bibcode:2001Icar..151...84K. “Subsurface oceans and deep interiors of medium-sized doi:10.1006/icar.2001.6599. outer planet satellites and large trans-neptunian objects” . Icarus 185: 258–273. Bibcode:2006Icar..185..258H. [104] Hammel, H. B.; Depater, I.; Gibbard, S. G.; Lock- doi:10.1016/j.icarus.2006.06.005. wood, G. W.; Rages, K. (May 2005). “New cloud activity on Uranus in 2004: First detection [117] Tittemore, William C.; Wisdom, Jack (June 1990). of a southern feature at 2.2 µm” (PDF). Icarus “Tidal evolution of the Uranian satellites: III. Evolu- 175 (1): 284–288. Bibcode:2005Icar..175..284H. tion through the Miranda-Umbriel 3:1, Miranda-Ariel 5:3, doi:10.1016/j.icarus.2004.11.016. and Ariel-Umbriel 2:1 mean-motion commensurabilities” . Icarus 85 (2): 394–443. Bibcode:1990Icar...85..394T. [105] Sromovsky, L.; Fry, P.;Hammel, H. and Rages, K.“Hub- doi:10.1016/0019-1035(90)90125-S. ble Discovers a Dark Cloud in the Atmosphere of Uranus” (PDF). physorg.com. Retrieved August 22, 2007. [118] Pappalardo, R. T., , S. J., , R. (1997). “Extensional tilt blocks on Miranda: Ev- [106] Hammel, H.B.; Lockwood, G.W. (2007). “Long- idence for an upwelling origin of Arden Corona” term atmospheric variability on Uranus and Neptune” . Journal of Geophysical Research 102 (E6): . Icarus 186: 291–301. Bibcode:2007Icar..186..291H. 13,369–13,380. Bibcode:1997JGR...10213369P. doi:10.1016/j.icarus.2006.08.027. doi:10.1029/97JE00802. 96 CHAPTER 6. URANUS

[119] Chaikin, Andrew (October 16, 2001). “Birth of Uranus' • NASA's Uranus fact sheet Provocative Moon Still Puzzles Scientists”. Space.Com. ImaginovaCorp. Archived from the original on 2008-07- • Uranus Profile at NASA's Solar System Exploration 09. Retrieved December 7, 2007. site

[120] Tittemore, W. C. (September 1990). “Tidal • Planets – Uranus A kid's guide to Uranus. heating of Ariel”. Icarus 87 (1): 110–139. • Bibcode:1990Icar...87..110T. doi:10.1016/0019- Uranus at Jet Propulsion Laboratory's planetary 1035(90)90024-4. photojournal. (photos)

[121] Gallardo, T. (2006). “Atlas of the mean mo- • Voyager at Uranus (photos) tion resonances in the Solar System”. Icarus • 184 (1): 29–38. Bibcode:2006Icar..184...29G. Uranus (Astronomy Cast homepage) (blog) doi:10.1016/j.icarus.2006.04.001. • Uranian system montage (photo) [122] de la Fuente Marcos, C. and de la Fuente Marcos, R. • Gray, Meghan; Merrifield, Michael (2010). (2013). “Crantor, a short-lived horseshoe companion “ ” to Uranus”. Astronomy and Astrophysics 551: A114. Uranus . Sixty Symbols. Brady Haran for the arXiv:1301.0770. Bibcode:2013A%26A...551A.114D. University of Nottingham. doi:10.1051/0004-6361/201220646.

[123] “Voyager: The Interstellar Mission: Uranus”. JPL. 2004. Retrieved June 9, 2007.

[124] Pappalardo, Bob and Spiker, Linda (2009-03-09). “Cassini Proposed Extended-Extended Mission (XXM)" (PDF). Retrieved 2011-08-20.

[125] Space Studies Board. “NRC planetary decadal survey 2013–2022”. NASA Lunar Science Institute. Retrieved 2011-08-05.

[126] Michael Schirber – Missions Proposed to Explore Mys- terious Tilted Planet Uranus (2011) – Astrobiology Magazine. Space.com. Retrieved on 2012-04-02.

[127] THE CASE FOR A URANUS ORBITER, Mark Hofs- tadter et al.

[128] To Uranus on Solar Power and Batteries. (PDF) . Re- trieved on 2012-04-02.

[129] Parker, Derek and Julia Aquarius. Planetary Zodiac Li- brary. New York: Mitchell Beazley/Ballantine Book. 1972. p. 14.

[130] “Uranium”. The American Heritage Dictionary of the English Language (4th ed.). Houghton Mifflin Company. Retrieved April 20, 2010.

[131] “On First Looking Into Chapman's Homer”. City Uni- versity of New York. 2009. Retrieved 2011-10-29.

6.15 Further reading

• Miner, Ellis D. (1998). Uranus: The Planet, Rings and Satellites. New York: John Wiley and Sons. ISBN 978-0-471-97398-0.

6.16 External links

• Uranus at European Space Agency Chapter 7

Venus

This article is about the planet. For other uses, see Venus (disambiguation).

Venus is the second planet from the Sun, orbiting it every 224.7 Earth days.*[10] It has no . It is named after the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows.*[11] Because Venus is an inferior planet Size comparison of Mercury, Venus, Earth and the Moon, Mars, from Earth, it never appears to venture far from the Sun: and Ceres on the far right. This may not be exactly to scale, because the visual disc of Venus with its atmosphere makes it its elongation reaches a maximum of 47.8°. look bigger than its solid-body diameter. Venus is a terrestrial planet and is sometimes called Earth's “sister planet”because of their similar size, mass, proximity to the Sun and bulk composition. It is radically different from Earth in other respects. It has the densest atmosphere of the four terrestrial plan- ets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is 92 times that of Earth's. With a mean surface temperature of 735 K (462 °C; 863 °F), Venus is by far the hottest planet in the Solar System, even though Mercury is closer to the Sun. Venus has no carbon cycle that puts carbon into rock, nor does it seem to have any organic life to ab- Size comparison with Earth. sorb carbon in biomass. Venus is shrouded by an opaque layer of highly reflective clouds of sulfuric acid, prevent- surface differ radically from those on Earth, owing to its ing its surface from being seen from space in visible light. * * dense carbon dioxide atmosphere. The mass of the atmo- It may have possessed oceans in the past, [12] [13] but sphere of Venus is 96.5% carbon dioxide, with most of these would have vaporized as the temperature rose due the remaining 3.5% being nitrogen.*[17] to a runaway greenhouse effect.*[14] The water has most probably photodissociated, and, because of the lack of a planetary magnetic field, the free hydrogen has been 7.1.1 Geography swept into interplanetary space by the solar wind.*[15] Venus' surface is a dry desertscape interspersed with slab- The Venusian surface was a subject of speculation un- like rocks and periodically refreshed by volcanism. til some of its secrets were revealed by planetary science in the 20th century. It was finally mapped in detail by Project in 1990–91. The ground shows evi- 7.1 Physical characteristics dence of extensive volcanism, and the sulfur in the atmo- sphere may indicate there have been some recent erup- * * Venus is one of the four terrestrial planets in the Solar tions. [18] [19] System, meaning that, like Earth, it is a rocky body. In About 80% of the Venusian surface is covered by smooth, size and mass, it is similar to Earth, and is often described volcanic plains, consisting of 70% plains with wrin- as Earth's “sister”or “twin”.*[16] The diameter of kle ridges and 10% smooth or lobate plains.*[20] Two Venus is 12,092 km (only 650 km less than Earth's) and highland“”make up the rest of its surface area, its mass is 81.5% of Earth's. Conditions on the Venusian one lying in the planet's northern hemisphere and the

97 98 CHAPTER 7. VENUS

other just south of the equator. The northern is called , after Ishtar, the Babylonian god- dess of love, and is about the size of Australia. , the highest mountain on Venus, lies on Ishtar Terra. Its peak is 11 km above the Venusian aver- age surface elevation. The southern continent is called Terra, after the Greek goddess of love, and is the larger of the two highland regions at roughly the size of . A network of fractures and faults cov- ers much of this area.*[21] The absence of evidence of lava flow accompanying any of the visible remains an enigma. The planet has few impact craters, demonstrating the surface is relatively young, approximately 300–600 million years old.*[22]*[23] In addition to the impact craters, moun- with a vertical exaggeration of 22.5 tains, and valleys commonly found on rocky planets, Venus has some unique surface features. Among these are flat-topped volcanic features called "farra", which look somewhat like pancakes and range in size from 20 to Several lines of evidence point to ongoing volcanic ac- 50 km across, and from 100 to 1,000 m high; radial, star- tivity on Venus. During the Soviet program, the like fracture systems called “novae"; features with both and probes detected a constant radial and concentric fractures resembling spider webs, stream of lightning, and Venera 12 recorded a power- known as "arachnoids"; and“coronae”, circular rings of ful clap of thunder soon after it landed. The European fractures sometimes surrounded by a depression. These Space Agency's recorded abundant light- features are volcanic in origin.*[24] ning in the high atmosphere.*[31] Although rainfall drives Most Venusian surface features are named after historical thunderstorms on Earth, there is no rainfall on the surface and mythological women.*[25] Exceptions are Maxwell of Venus (though sulfuric acid rain falls in the upper at- Montes, named after James Clerk Maxwell, and high- mosphere, then evaporates around 25 km above the sur- land regions , and . face). One possibility is that ash from a volcanic eruption The former three features were named before the cur- was generating the lightning. Another piece of evidence rent system was adopted by the International Astronom- comes from measurements of sulfur dioxide concentra- ical Union, the body that oversees planetary nomencla- tions in the atmosphere, which dropped by a factor of 10 ture.*[26] between 1978 and 1986. This may mean the levels had earlier been boosted by a large volcanic eruption.*[32] The longitudes of physical features on Venus are ex- Almost a thousand impact craters on Venus are evenly pressed relative to its prime meridian. The original prime distributed across its surface. On other cratered bodies, meridian passed through the radar-bright spot at the cen- such as Earth and the Moon, craters show a range of states ter of the oval feature Eve, located south of Alpha Re- of degradation. On the Moon, degradation is caused by * gio. [27] After the Venera missions were completed, the subsequent impacts, whereas on Earth it is caused by wind prime meridian was redefined to pass through the central and rain erosion. On Venus, about 85% of the craters * * peak in the crater . [28] [29] are in pristine condition. The number of craters, to- gether with their well-preserved condition, indicates the planet underwent a global resurfacing event about 300– 7.1.2 Surface geology 600 million years ago,*[22]*[23] followed by a decay in volcanism.*[33] Whereas Earth's crust is in continuous Main article: motion, Venus is thought to be unable to sustain such a Much of the Venusian surface appears to have been process. Without plate tectonics to dissipate heat from shaped by volcanic activity. Venus has several times its mantle, Venus instead undergoes a cyclical process in as many volcanoes as Earth, and it possesses 167 large which mantle temperatures rise until they reach a criti- volcanoes that are over 100 km across. The only vol- cal level that weakens the crust. Then, over a period of canic complex of this size on Earth is the Big Island about 100 million years, subduction occurs on an enor- of Hawaii.*[24] This is not because Venus is more vol- mous scale, completely recycling the crust.*[24] In March canically active than Earth, but because its crust is 2014, the first direct evidence for ongoing volcanism was older. Earth's oceanic crust is continually recycled by located, in the form of infrared “flashes”over the subduction at the boundaries of tectonic plates, and has zone Ganiki , near the shield volcano Maat Mons. an average age of about 100 million years,*[30] whereas These flashes, ranging from 40 to 320 °C above the am- the Venusian surface is estimated to be 300–600 million bient, are believed to be either hot gases or lava released years old.*[22]*[24] from volcanic eruptions.*[34] 7.1. PHYSICAL CHARACTERISTICS 99

Venusian craters range from 3 km to 280 km in diameter. 7.1.4 Atmosphere and climate No craters are smaller than 3 km, because of the effects of the dense atmosphere on incoming objects. Objects with less than a certain kinetic energy are slowed down so much by the atmosphere that they do not create an im- pact crater.*[35] Incoming projectiles less than 50 metres in diameter will fragment and burn up in the atmosphere before reaching the ground.*[36]

7.1.3 Internal structure

Cloud structure in the Venusian atmosphere in 1979, revealed by observations in the ultraviolet band by

Global radar view of Venus (without the clouds) from The internal structure of Venus – the crust (outer layer), the man- the Magellan imaging between 1990 and 1994 tle (middle layer) and the core (yellow inner layer)

Without seismic data or knowledge of its moment of iner- tia, little direct information is available about the internal structure and geochemistry of Venus.*[37] The similar- ity in size and density between Venus and Earth suggests they share a similar internal structure: a core, mantle, and crust. Like that of Earth, the Venusian core is at least partially liquid because the two planets have been cool- ing at about the same rate.*[38] The slightly smaller size of Venus suggests pressures are significantly lower in its deep interior than Earth. The principal difference be- Impact craters on the surface of Venus (image recon- tween the two planets is the lack of evidence for plate tec- structed from radar data) tonics on Venus, possibly because its crust is too strong Main article: to subduct without water to make it less viscous. This results in reduced heat loss from the planet, preventing Venus has an extremely dense atmosphere, which con- it from cooling and providing a likely explanation for its sists mainly of carbon dioxide and a small amount of lack of an internally generated magnetic field.*[39] In- nitrogen. The atmospheric mass is 93 times that of stead, Venus may lose its internal heat in periodic major Earth's atmosphere, whereas the pressure at the planet's resurfacing events.*[22] surface is about 92 times that at Earth's surface—a pres- 100 CHAPTER 7. VENUS

sure equivalent to that at a depth of nearly 1 kilometre —also minimizes seasonal temperature variation.*[54] under Earth's oceans. The density at the surface is 65 The only appreciable variation in temperature occurs with kg/m3, 6.5% that of water or 50 times as dense as Earth's altitude. The highest point on Venus, Maxwell Montes, is atmosphere at 20 °C at sea level. The CO2-rich atmo- therefore the coolest point on the planet, with a temper- sphere, along with thick clouds of sulfur dioxide, gen- ature of about 655 K (380 °C) and an atmospheric pres- erates the strongest greenhouse effect in the Solar Sys- sure of about 4.5 MPa (45 bar).*[55]*[56] In 1995, the tem, creating surface temperatures of at least 735 K (462 Magellan probe imaged a highly reflective substance at °C).*[10]*[40] This makes the Venusian surface hotter the tops of the highest mountain peaks that bore a strong than Mercury's, which has a minimum surface temper- resemblance to terrestrial snow. This substance arguably ature of 55 K (−220 °C) and maximum surface tem- formed from a similar process to snow, albeit at a far perature of 695 K (420 °C),*[41] even though Venus is higher temperature. Too volatile to condense on the sur- nearly twice Mercury's distance from the Sun and thus face, it rose in gas form to cooler higher elevations, where receives only 25% of Mercury's solar irradiance. The it then fell as precipitation. The identity of this substance surface of Venus is often described as hellish.*[42] This is not known with certainty, but speculation has ranged temperature is higher than temperatures used to achieve from elemental tellurium to lead sulfide (galena).*[57] sterilization. The clouds of Venus are capable of producing lightning Studies have suggested that billions of years ago the Venu- much like the clouds on Earth.*[58] The existence of sian atmosphere was much more like Earth's than it is lightning had been controversial since the first sus- now, and that there may have been substantial quantities pected bursts were detected by the Soviet Venera of liquid water on the surface, but after a period of 600 probes. In 2006–2007 Venus Express clearly detected million to several billion years,*[43] a runaway green- whistler mode waves, the signatures of lightning. Their house effect was caused by the evaporation of that origi- intermittent appearance indicates a pattern associated nal water, which generated a critical level of greenhouse with weather activity. The lightning rate is at least half gases in its atmosphere.*[44] Although the surface condi- of that on Earth.*[58] In 2007 the Venus Express probe tions on the planet are no longer hospitable to any Earth- discovered that a huge double atmospheric vortex exists like life that may have formed before this event, it is pos- at the south pole.*[59]*[60] sible that life exists in the lower and middle cloud layers * * * Another discovery made by the Venus Express probe in of Venus. [45] [46] [47] 2011 is that an ozone layer exists high in the atmosphere Thermal inertia and the transfer of heat by winds in the of Venus.*[61] lower atmosphere mean that the temperature of the Venu- On January 29, 2013, ESA scientists reported that the sian surface does not vary significantly between the night ionosphere of the planet Venus streams outwards in a and day sides, despite the planet's extremely slow rota- manner similar to “the ion tail seen streaming from a tion. Winds at the surface are slow, moving at a few kilo- comet under similar conditions.”*[62]*[63] metres per hour, but because of the high density of the atmosphere at the Venusian surface, they exert a signifi- Atmospheric composition cant amount of force against obstructions, and transport dust and small stones across the surface. This alone would make it difficult for a human to walk through, even if the heat, pressure and lack of oxygen were not a prob- lem.*[48]

Above the dense CO2 layer are thick clouds con- sisting mainly of sulfur dioxide and sulfuric acid droplets.*[49]*[50] These clouds reflect and scatter about 90% of the sunlight that falls on them back into space, and prevent visual observation of the Venusian surface. The permanent cloud cover means that although Venus is Synthetic stick absorption spectrum of a simple gas mix- closer than Earth to the Sun, the Venusian surface is not as ture corresponding to Earth's atmosphere well lit. Strong 85 m/s (300 km/h) winds at the cloud tops circle the planet about every four to five Earth days.*[51] Venusian winds move at up to 60 times the speed of the planet's rotation, whereas Earth's fastest winds are only 10–20% rotation speed.*[52] The surface of Venus is effectively isothermal; it retains a constant temperature not only between day and night but between the equator and the poles.*[1]*[53] The planet's minute axial tilt—less than 3°, compared to 23° on Earth 7.2. ORBIT AND ROTATION 101

Venusian atmosphere composition based on HITRAN mosphere by 150 times compared to the ratio in the lower data*[64] created using Hitran on the Web system.*[65] atmosphere.*[73] Green colour – water vapour, red – carbon dioxide, WN – wavenumber (other colours have different meanings, lower wavelengths on the right, higher on the left). 7.2 Orbit and rotation

7.1.5 Magnetic field and core

In 1967, found the Venusian magnetic field to be much weaker than that of Earth. This magnetic field is induced by an interaction between the ionosphere and the solar wind,*[66]*[67] rather than by an internal dynamo in the core like the one inside Earth. Venus's small induced magnetosphere provides negligible protection to the atmosphere against cosmic radiation. This radiation may result in cloud-to-cloud lightning discharges.*[68] The lack of an intrinsic magnetic field at Venus was sur- prising given it is similar to Earth in size, and was ex- pected also to contain a dynamo at its core. A dynamo requires three things: a conducting liquid, rotation, and convection. The core is thought to be electrically con- ductive and, although its rotation is often thought to be too slow, simulations show it is adequate to produce a dynamo.*[69]*[70] This implies the dynamo is missing Venus orbits the Sun at an average distance of about 108 million because of a lack of convection in the Venusian core. On kilometres (about 0.7 AU) and completes an orbit every 224.65 days. Venus is the second planet from the Sun and orbits the Sun Earth, convection occurs in the liquid outer layer of the approximately 1.6 times (yellow trail) in Earth's 365 days (blue core because the bottom of the liquid layer is much hotter trail) than the top. On Venus, a global resurfacing event may have shut down plate tectonics and led to a reduced heat Venus orbits the Sun at an average distance of about 0.72 flux through the crust. This caused the mantle tempera- AU (108,000,000 km; 67,000,000 mi), and completes an ture to increase, thereby reducing the heat flux out of the orbit every 224.65 days. Although all planetary orbits are core. As a result, no internal geodynamo is available to elliptical, Venus's orbit is the closest to circular, with an drive a magnetic field. Instead, the heat energy from the * * eccentricity of less than 0.01. [1] When Venus lies be- core is being used to reheat the crust. [71] tween Earth and the Sun, a position known as inferior One possibility is that Venus has no solid inner core,*[72] conjunction, it makes the closest approach to Earth of or that its core is not cooling, so that the entire liquid any planet at an average distance of 41 million km.*[1] part of the core is at approximately the same tempera- The planet reaches inferior conjunction every 584 days, ture. Another possibility is that its core has already com- on average.*[1] Owing to the decreasing eccentricity of pletely solidified. The state of the core is highly depen- Earth's orbit, the minimum distances will become greater dent on the concentration of sulfur, which is unknown at over tens of thousands of years. From the year 1 to 5383, present.*[71] there are 526 approaches less than 40 million km; then * The weak magnetosphere around Venus means that the there are none for about 60,158 years. [74] solar wind is interacting directly with its outer atmo- All the planets of the Solar System orbit the Sun in an sphere. Here, ions of hydrogen and oxygen are being anti-clockwise direction as viewed from above Earth's created by the dissociation of neutral molecules from ul- north pole. Most planets also rotate on their axes in traviolet radiation. The solar wind then supplies energy an anti-clockwise direction, but Venus rotates clock- that gives some of these ions sufficient velocity to es- wise (called "retrograde" rotation) once every 243 Earth cape Venus's gravity field. This erosion process results days —the slowest rotation period of any planet. Be- in a steady loss of low-mass hydrogen, helium, and oxy- cause its rotation is so slow, it is highly spherical.*[75] gen ions, whereas higher-mass molecules, such as carbon A Venusian sidereal day thus lasts longer than a Venu- dioxide, are more likely to be retained. Atmospheric ero- sian year (243 versus 224.7 Earth days). Venus's equa- sion by the solar wind probably led to the loss of most tor rotates at 6.5 km/h (4.0 mph), whereas Earth's is ap- of Venus's water during the first billion years after it proximately 1,670 km/h (1,040 mph).*[76] Venus's ro- formed. The erosion has increased the ratio of higher- tation has slowed down by 6.5 min per Venusian sidereal mass deuterium to lower-mass hydrogen in the upper at- day in the 16 years between the Magellan spacecraft and 102 CHAPTER 7. VENUS

Venus Express visits.*[77] Because of the retrograde ro- tation, the length of a solar day on Venus is significantly shorter than the sidereal day, at 116.75 Earth days (mak- ing the Venusian solar day shorter than Mercury's 176 Earth days); one Venusian year is about 1.92 Venusian (solar) days long.*[78] To an observer on the surface of Venus, the Sun would rise in the west and set in the east, though the Sun cannot be seen from the surface due to Venus's opaque clouds.*[78] Venus may have formed from the solar nebula with a dif- ferent rotation period and obliquity, reaching its current state because of chaotic spin changes caused by planetary Venus is always brighter than the brightest stars outside the Solar perturbations and tidal effects on its dense atmosphere, a System, as can be seen here over the Pacific Ocean change that would have occurred over the course of bil- lions of years. The rotation period of Venus may rep- resent an equilibrium state between to the Sun's gravitation, which tends to slow rotation, and an at- mospheric created by solar heating of the thick Venu- sian atmosphere.*[79]*[80] The 584-day average interval between successive close approaches to Earth is almost exactly equal to 5 Venusian solar days,*[81] but the hy- pothesis of a spin–orbit resonance with Earth has been discounted.*[82] Venus has no natural satellites,*[83] though the asteroid 2002 VE68 presently maintains a quasi-orbital relation- ship with it.*[84]*[85] Besides this quasi-satellite, it has two other temporary co-orbitals, 2001 CK32 and 2012 XE133.*[86] In the 17th century, Giovanni Cassini re- ported a moon orbiting Venus, which was named Neith and numerous sightings were reported over the following 200 years, but most were determined to be stars in the vicinity. Alex Alemi's and David Stevenson's 2006 study of models of the early Solar System at the California In- and evolution of its apparent diameter stitute of Technology shows Venus likely had at least one moon created by a huge impact event billions of years * ago. [87] About 10 million years later, according to the Sun.*[1] As it does so, it changes from the “Evening study, another impact reversed the planet's spin direction Star”, visible after , to the “Morning Star”, vis- and caused the Venusian moon gradually to spiral inward ible before sunrise. Although Mercury, the other inferior * until it collided and merged with Venus. [88] If later im- planet, reaches a maximum elongation of only 28° and pacts created moons, these were absorbed in the same is often difficult to discern in twilight, Venus is hard to way. An alternative explanation for the lack of satellites miss when it is at its brightest. Its greater maximum elon- is the effect of strong solar , which can destabilize gation means it is visible in dark skies long after sunset. * large satellites orbiting the inner terrestrial planets. [83] As the brightest point-like object in the sky, Venus is a commonly misreported "unidentified flying object". U.S. President Jimmy Carter reported having seen a UFO in 1969, which later analysis suggested was probably Venus. 7.3 Observation Countless other people have mistaken Venus for some- thing more exotic.*[90] Venus is always brighter than any star (apart from the As it moves around its orbit, Venus displays phases like Sun). The greatest luminosity, apparent magnitude * those of the Moon in a telescopic view. The planet −4.9, [8] occurs during crescent phase when it is near presents a small “full”image when it is on the opposite Earth. Venus fades to about magnitude −3 when it is side of the Sun. It shows a larger “quarter phase”when backlit by the Sun.*[7] The planet is bright enough to be * it is at its maximum elongations from the Sun, and is at seen in a mid-day clear sky, [89] and it can be easy to see its brightest in the night sky, and presents a much larger when the Sun is low on the horizon. As an inferior planet, “ ” * thin crescent in telescopic views as it comes around to it always lies within about 47° of the Sun. [9] the near side between Earth and the Sun. Venus is at its Venus “overtakes”Earth every 584 days as it orbits the largest and presents its “new phase”when it is between 7.4. STUDIES 103

Earth and the Sun. Its atmosphere can be seen in a tele- 7.3.2 Ashen light scope by the halo of light refracted around it.*[9] A long-standing mystery of Venus observations is the so- called ashen light—an apparent weak illumination of its dark side, seen when the planet is in the crescent phase. The first claimed observation of ashen light was made in 7.3.1 Transits 1643, but the existence of the illumination has never been reliably confirmed. Observers have speculated it may re- sult from electrical activity in the Venusian atmosphere, but it could be illusory, resulting from the physiological effect of observing a bright, crescent-shaped object.*[97]

7.4 Studies

7.4.1 Early studies

2004

Main articles: Transits of Venus and Transit of Venus, 2012

The Venusian orbit is slightly inclined relative to Earth's orbit; thus, when the planet passes between Earth and the Sun, it usually does not cross the face of the Sun. Transits of Venus occur when the planet's inferior conjunction co- incides with its presence in the plane of Earth's orbit. Transits of Venus occur in cycles of 243 years with the current pattern of transits being pairs of transits separated The "black drop effect" as recorded during the 1769 transit by eight years, at intervals of about 105.5 years or 121.5 years—a pattern first discovered in 1639 by the English * Venus was known to ancient civilizations both as the astronomer . [91] “morning star”and as the “evening star”, names that The latest pair was June 8, 2004 and June 5–6, 2012. The reflect the early assumption that these were two separate transit could be watched live from many online outlets objects. The Venus tablet of Ammisaduqa, dated 1581 or observed locally with the right equipment and condi- BCE, shows the Babylonians understood the two were tions.*[92] a single object, referred to in the tablet as the “bright queen of the sky”, and could support this view with de- The preceding pair of transits occurred in December * 1874 and December 1882; the following pair will occur in tailed observations. [98] The Greeks thought of the two * as separate stars, Phosphorus and , until the time December 2117 and December 2125. [93] Historically, * transits of Venus were important, because they allowed of Pythagoras in the sixth century BC. [99] The Romans astronomers to determine the size of the astronomical designated the morning aspect of Venus as Lucifer, liter- “ ” unit, and hence the size of the Solar System as shown ally Light-Bringer , and the evening aspect as Vesper, by Horrocks in 1639.*[94] Captain 's exploration both literal translations of the respective Greek names. of the east coast of Australia came after he had sailed The transit of Venus was first observed in 1032 by the to Tahiti in 1768 to observe a transit of Venus.*[95]*[96] Persian astronomer , who concluded Venus is 104 CHAPTER 7. VENUS

closer to Earth than the Sun,*[100] and established Venus was, at least sometimes, below the Sun.*[101] In the 12th century, the Andalusian astronomer Ibn Bajjah observed “two planets as black spots on the face of the Sun”, which were later identified as the transits of Venus and Mercury by the Maragha astronomer Qotb al-Din Shirazi in the 13th century.*[102] The transit of Venus was also ob- served by Jeremiah Horrocks on 4 December 1639 (24 November under the Julian calendar in use at that time), along with his friend, , at each of their respective homes.*[103]

Modern telescopic view of Venus from Earth's surface

7.4.2 Ground-based research

Little more was discovered about Venus until the 20th century. Its almost featureless disc gave no hint what its surface might be like, and it was only with the develop- ment of spectroscopic, radar and ultraviolet observations EARTH that more of its secrets were revealed. The first UV obser- vations were carried out in the 1920s, when Frank E. Ross found that UV photographs revealed considerable detail Galileo's discovery that Venus showed phases (although remain- that was absent in visible and infrared radiation. He sug- ing near the Sun in Earth's sky) proved that it orbits the Sun and not Earth gested this was due to a dense, yellow lower atmosphere with high cirrus clouds above it.*[110] Spectroscopic observations in the 1900s gave the first clues about the Venusian rotation. Vesto tried When the Italian physicist Galileo Galilei first observed to measure the shift of light from Venus, but the planet in the early 17th century, he found it showed found he could not detect any rotation. He surmised the phases like the Moon, varying from crescent to gibbous to planet must have a much longer rotation period than had full and vice versa. When Venus is furthest from the Sun previously been thought.*[111] Later work in the 1950s in the sky, it shows a half-lit phase, and when it is closest showed the rotation was retrograde. Radar observations to the Sun in the sky, it shows as a crescent or full phase. of Venus were first carried out in the 1960s, and provided This could be possible only if Venus orbited the Sun, and the first measurements of the rotation period, which were this was among the first observations to clearly contradict close to the modern value.*[112] the Ptolemaic that the Solar System was concentric and centered on Earth.*[104]*[105] Radar observations in the 1970s revealed details of the Venusian surface for the first time. Pulses of radio waves The atmosphere of Venus was discovered in 1761 by Rus- were beamed at the planet using the 300 m (980 ft) ra- sian polymath Mikhail Lomonosov.*[106]*[107] Venus's dio telescope at Arecibo Observatory, and the echoes re- atmosphere was observed in 1790 by German astronomer vealed two highly reflective regions, designated the Alpha Johann Schröter. Schröter found when the planet was a and Beta regions. The observations also revealed a bright thin crescent, the cusps extended through more than 180°. region attributed to mountains, which was called Maxwell He correctly surmised this was due to scattering of sun- Montes.*[113] These three features are now the only ones light in a dense atmosphere. Later, American astronomer on Venus that do not have female names.*[114] Chester Smith Lyman observed a complete ring around the dark side of the planet when it was at inferior conjunc- tion, providing further evidence for an atmosphere.*[108] The atmosphere complicated efforts to determine a rota- tion period for the planet, and observers such as Italian- 7.5 Exploration astronomer Giovanni Cassini and Schröter incor- rectly estimated periods of about 24 h from the motions Main article: Observations and explorations of Venus of markings on the planet's apparent surface.*[109] 7.5. EXPLORATION 105

7.5.1 Early efforts

Mariner 2, launched in 1962

The first robotic space probe mission to Venus, and the first to any planet, began on 12 February 1961, with the launch of the Venera 1 probe. The first craft of the oth- erwise highly successful Soviet Venera program, Venera 1 was launched on a direct impact trajectory, but contact was lost seven days into the mission, when the probe was about 2 million km from Earth. It was estimated to have reading was 18 bar at an altitude of 24.96 km.*[118] passed within 100,000 km of Venus in mid-May.*[115] One day later on 19 October 1967, conducted The United States exploration of Venus also started badly a fly-by at a distance of less than 4000 km above the cloud with the loss of the probe on launch. The sub- tops. Mariner 5 was originally built as a backup for the sequent mission, after a 109-day transfer orbit Mars-bound ; when that mission was success- on 14 December 1962, became the world's first success- ful, the probe was refitted for a Venus mission. A suite ful interplanetary mission, passing 34,833 km above the of instruments more sensitive than those on Mariner 2, in surface of Venus. Its microwave and infrared radiometers particular its radio occultation experiment, returned data revealed that although the Venusian cloud tops were cool, on the composition, pressure and density of the Venu- the surface was extremely hot—at least 425 °C, confirm- sian atmosphere.*[119] The joint Venera 4 – Mariner ing previous Earth-based measurements*[116] and finally 5 data was analysed by a combined Soviet-American ending any hopes that the planet might harbour ground- science team in a series of colloquia over the follow- based life. Mariner 2 also obtained improved estimates ing year,*[120] in an early example of space coopera- of its mass and of the , but was unable tion.*[121] to detect either a magnetic field or radiation belts.*[117] Armed with the lessons and data learned from Venera 4, the launched the twin probes Venera 5 and 7.5.2 Atmospheric entry five days apart in January 1969; they encoun- tered Venus a day apart on 16 and 17 May. The probes The Soviet probe crash-landed on Venus on 1 were strengthened to improve their crush depth to 25 bar March 1966. It was the first man-made object to enter the and were equipped with smaller parachutes to achieve a atmosphere and strike the surface of another planet. Its faster descent. Because then-current atmospheric models communication system failed before it was able to return of Venus suggested a surface pressure of between 75 and any planetary data.*[118] On 18 October 1967, Venera 4 100 bar, neither was expected to survive to the surface. successfully entered the atmosphere and deployed science After returning atmospheric data for a little over 50 min- experiments. Venera 4 showed the surface temperature utes, they were both crushed at altitudes of approximately was even hotter than Mariner 2 had measured, at almost 20 km before going on to strike the surface on the night 500 °C, and the atmosphere was 90 to 95% carbon diox- side of Venus.*[118] ide. The Venusian atmosphere was considerably denser than Venera 4's designers had anticipated, and its slower than intended parachute descent meant its batteries ran 7.5.3 Surface and atmospheric science down before the probe reached the surface. After return- ing descent data for 93 minutes, Venera 4's last pressure Venera 7 represented an effort to return data from the 106 CHAPTER 7. VENUS

planet's surface, and was constructed with a reinforced separate missions.*[124] The Pioneer Venus Orbiter was descent module capable of withstanding a pressure of inserted into an elliptical orbit around Venus on 4 Decem- 180 bar. The module was precooled before entry and ber 1978, and remained there for over 13 years, study- equipped with a specially reefed parachute for a rapid 35- ing the atmosphere and mapping the surface with radar. minute descent. While entering the atmosphere on 15 The Pioneer Venus Multiprobe released a total of four December 1970, the parachute is believed to have par- probes, which entered the atmosphere on 9 December tially torn, and the probe struck the surface with a hard, 1978, returning data on its composition, winds and heat yet not fatal, impact. Probably tilted onto its side, it re- fluxes.*[125] turned a weak signal, supplying temperature data for 23 minutes, the first telemetry received from the surface of another planet.*[118]

180-degree panorama of the Venusian surface from the Soviet lander

The Venera program continued with sending data from the surface for 50 minutes, after entering the atmosphere on 22 July 1972. Venera 9, which entered the atmosphere of Venus on 22 October 1975, and Venera Position of Venera landing sites returning images form the sur- 10, which entered the atmosphere three days later, sent face the first images of the Venusian landscape. The two land- ing sites presented different terrains in the immediate vicinities of the landers: Venera 9 had landed on a 20- Four more Venera lander missions took place over the degree slope scattered with boulders around 30–40 cm next four years, with Venera 11 and Venera 12 detect- across; Venera 10 showed basalt-like rock slabs inter- ing Venusian electrical storms;*[126] and and spersed with weathered material.*[122] , landing on 1 and 5 March 1982, returning the first colour photographs of the surface. All four mis- sions deployed parachutes for braking in the upper at- mosphere, then released them at altitudes of 50 km, the dense lower atmosphere providing enough friction to al- low for unaided soft landings. Both Venera 13 and 14 analysed soil samples with an on-board X-ray fluores- cence spectrometer, and attempted to measure the com- pressibility of the soil with an impact probe.*[126] Ven- era 14 struck its own ejected camera lens cap and its probe failed to contact the soil.*[126] The Venera pro- gram came to a close in October 1983, when and Venera 16 were placed in orbit to conduct mapping of the Venusian terrain with synthetic aperture radar.*[127] In 1985, the Soviet Union took advantage of the oppor- tunity to combine missions to Venus and Comet , The Pioneer Venus orbiter which passed through the inner Solar System that year. En route to Halley, on 11 and 15 June 1985, the two In the meantime, the United States had sent the Mariner spacecraft of the each dropped a Venera- 10 probe on a gravitational slingshot trajectory past Venus style probe (of which 's partially failed) and re- on its way to Mercury. On 5 February 1974, leased a balloon-supported aerobot into the upper atmo- passed within 5790 km of Venus, returning over 4000 sphere. The balloons achieved an equilibrium altitude of photographs as it did so. The images, the best then around 53 km, where pressure and temperature are com- achieved, showed the planet to be almost featureless in parable to those at Earth's surface. They remained op- visible light, but ultraviolet light revealed details in the erational for around 46 hours, and discovered the Venu- clouds that had never been seen in Earth-bound observa- * sian atmosphere was more turbulent than previously be- tions. [123] lieved, and subject to high winds and powerful convection The American consisted of two cells.*[128]*[129] 7.5. EXPLORATION 107

7.5.4 Radar mapping their respective missions to the outer planets, but Mag- ellan was the last dedicated mission to Venus for over a decade.*[132]*[133]

7.5.5 Current and future missions

NASA's MESSENGER mission to Mercury performed two fly-bys of Venus in October 2006 and June 2007, to slow its trajectory for an eventual orbital insertion of Mer- cury in March 2011. It collected scientific data on Venus during both fly-bys.*[134] The Venus Express probe was designed and built by the European Space Agency. Launched on 9 Novem- ber 2005 by a Russian Soyuz-Fregat rocket procured through Starsem, it successfully assumed a polar orbit around Venus on 11 April 2006.*[135] The probe is un- dertaking a detailed study of the Venusian atmosphere and clouds, including mapping of the planet's plasma en- vironment and surface characteristics, particularly tem- peratures. One of the first results from Venus Express is Magellan radar topographical map of Venus (false colour) the discovery that a huge double atmospheric vortex ex- ists at the southern pole.*[135]

Artist's impression of a Stirling cooled Venus Rover.*[136]

The Japan Aerospace Exploration Agency (JAXA) de- vised a Venus orbiter, (formerly“Planet-C”), which was launched on 20 May 2010, but the craft failed Five global views of Venus by Magellan. to enter orbit in December 2010. Hopes remain that the probe can successfully hibernate and make another in- Early Earth-based radar provided a basic idea of the sur- sertion attempt in six years. Planned investigations in- face. The Pioneer Venus and the Veneras provided im- cluded surface imaging with an infrared camera and ex- proved resolution. periments designed to confirm the presence of lightning, The United States' Magellan probe was launched on 4 as well as the determination of the existence of current * May 1989, with a mission to map the surface of Venus surface volcanism. [137] with radar.*[26] The high-resolution images it obtained The European Space Agency (ESA) hopes to launch a during its 4½ years of operation far surpassed all prior mission to Mercury in 2016, called BepiColombo, which maps and were comparable to visible-light photographs will perform two fly-bys of Venus before it reaches Mer- of other planets. Magellan imaged over 98% of the cury orbit in 2020.*[138]*[139] Venusian surface by radar,*[130] and mapped 95% of its gravity field. In 1994, at the end of its mission, Mag- NASA will launch the Solar Probe Plus in 2018, which will perform seven Venus fly-bys during its six-year, 24- ellan was sent to its destruction into the atmosphere of * Venus to quantify its density.*[131] Venus was observed orbit reconnaissance of the Sun. [140] by the Galileo and Cassini spacecraft during fly-bys on Under its , NASA has proposed a 108 CHAPTER 7. VENUS

lander mission called the Venus In-Situ Explorer to land sample return by slowing down and entering then return- on Venus to study surface conditions and investigate the ing, and a surface sample return.*[145] elemental and mineralogical features of the regolith. The probe would be equipped with a core sampler to drill into the surface and study pristine rock samples not weath- 7.5.8 Spacecraft timeline ered by the harsh surface conditions. A Venus atmo- spheric and surface probe mission, “Surface and Atmo- This is a list of attempted and successful spacecraft that sphere Geochemical Explorer”(SAGE), was selected by have left Earth to explore Venus more closely.*[146] NASA as a candidate mission study in the 2009 New Venus has also been imaged by the Hubble Space Tele- Frontiers selection,*[141] but the mission was not se- scope in Earth orbit, and distant telescopic observations lected for flight. are another source of information about Venus.

Venera-D is a possible Russian mission in the 2020s*[148]

7.6 In culture

See also Venus (mythology), Venus (astrology) and Historical observations and impact Throughout history and cultures, the planet has been of remarkable importance as an especial object of observa- Venus aircraft concept tion, reflection and projection. Popular beliefs and obser- vations resulted in different and in parts similar patterns The Venera-D (Russian: Венера-Д) probe is a proposed in mythology as well as phenomenological descriptions, Russian space probe to Venus, to be launched around attributions and depictions, e.g. in astrology. Such devel- 2016, to make remote-sensing observations around the opments in manifestations of human thought reflect the planet and deploying a lander, based on the Venera de- planet's image as a result of early observations of Venus sign, capable of surviving for a long duration on the sur- and their impact on culture and science. face. Other proposed Venus exploration concepts include rovers, balloons, and aeroplanes.*[142] In late 2013 the Venus Spectral Rocket Experiment took 7.6.1 Etymology place, which launched a sub-orbital space telescope. The adjective Venusian is commonly used for items re- lated to Venus, though the Latin adjective is the rarely 7.5.6 Manned fly-by concept used Venerean; the archaic is still occasion- ally encountered. Venus is the only planet in the Solar Main article: Manned Venus Flyby System that is named after a female figure.*[lower-alpha 1] (Three dwarf planets —Ceres, and — * A manned Venus fly-by mission, using along with many of the first discovered asteroids [149] hardware, was proposed in the late 1960s.*[143] The and some moons (such as the Galilean moons) also have mission was planned to launch in late October or early feminine names. Earth and the Moon also have feminine — — November 1973, and would have used a Saturn V to send names in many languages Gaia/Terra, Selene/Luna but the female mythological figures who personified them three men to fly past Venus in a flight lasting approxi- * mately one year. The spacecraft would have passed ap- were named after them, not the other way around.) [150] proximately 5,000 km (3,100 mi) from the surface of Venus about four months later.*[143] Inspiration Mars in- cludes a manned Venus flyby in their 2021 mission.*[144] 7.6.2 Venus symbol

Main article: Venus symbol 7.5.7 Sample return The astronomical symbol for Venus is the same as that used in biology for the female sex: a circle with a small Various concepts for a Venus sample return include a cross beneath.*[151] The Venus symbol also represents high-speed upper atmosphere collection, an atmosphere femininity, and in Western alchemy stood for the metal 7.8. SEE ALSO 109

and oxygen) would be a lifting gas in the Venusian at- mosphere of mostly carbon dioxide. This has led to proposals for “floating cities”in the Venusian atmo- sphere.*[152] Aerostats (lighter-than-air balloons) could be used for initial exploration and ultimately for per- manent settlements.*[152] Among the many engineering challenges are the dangerous amounts of sulfuric acid at these heights.*[152]

7.8 See also

•

• Mariner 10 Space probe to Venus

• 2001 CK32

• 2002 VE68 • 2012 XE133 copper.*[151] Polished copper has been used for mir- • Geodynamics of Venus rors from antiquity, and the symbol for Venus has some- • times been understood to stand for the mirror of the god- Geology of Venus * dess. [151] • Observations and explorations of Venus

• Venus zone 7.7 Colonization and terraforming

Main articles: Colonization of Venus and Terraforming 7.9 Notes of Venus Owing to its extremely hostile conditions, a surface [1] Goddesses such as Gaia and Terra were named after Earth, and not vice versa.

7.10 References

[1] Williams, David R. (15 April 2005).“Venus Fact Sheet” . NASA. Retrieved 2007-10-12.

[2] Yeomans, Donald K. “HORIZONS Web-Interface for Venus (Major Body=2)". JPL Horizons On-Line Ephemeris System.—Select “Ephemeris Type: Orbital Elements”,“Time Span: 2000-01-01 12:00 to 2000-01- 02”.(“Target Body: Venus”and“Center: Sun”should be defaulted to.) Results are instantaneous osculating values at the precise J2000 epoch.

[3] “The MeanPlane (Invariable plane) of the Solar System passing through the barycenter”. 3 April 2009. Retrieved 2009-04-10. (produced with Solex 10 written by Aldo Vitagliano; see also Invariable plane)

[4] Seidelmann, P. Kenneth; Archinal, Brent A.; A'Hearn, Artist's conception of a terraformed Venus Michael F. et al. (2007). “Report of the IAU/IAG Working Group on cartographic coordinates and colony on Venus is not possible with current technol- rotational elements: 2006”. Celestial Mechan- ogy. The atmospheric pressure and temperature ap- ics and Dynamical Astronomy 98 (3): 155–180. proximately fifty kilometres above the surface are sim- Bibcode:2007CeMDA..98..155S. doi:10.1007/s10569- ilar to those at Earth's surface and Earth air (nitrogen 007-9072-y. 110 CHAPTER 7. VENUS

[5] “Report on the IAU/IAG Working Group on cartographic [20] Basilevsky, Alexander T.; Head, James W., III (1995). coordinates and rotational elements of the planets and “Global stratigraphy of Venus: Analysis of a random sam- satellites”. International Astronomical Union. 2000. Re- ple of thirty-six test areas”. Earth, Moon, and Plan- trieved 2007-04-12. ets 66 (3): 285–336. Bibcode:1995EM&P...66..285B. doi:10.1007/BF00579467. [6] Mallama, A.; Wang, D.; Howard, R.A. (2006). “Venus phase function and forward scattering from H2SO4". [21] Kaufmann, W. J. (1994). Universe. New York: W. H. Icarus 182 (1): 10–22. Bibcode:2006Icar..182...10M. Freeman. p. 204. ISBN 0-7167-2379-4. doi:10.1016/j.icarus.2005.12.014. [22] Nimmo, F.; McKenzie, D. (1998). “Volcanism and Tec- [7] Mallama, A. (2011). “Planetary magnitudes”. Sky and tonics on Venus”. Annual Review of Earth and Planetary Telescope 121 (1): 51–56. Sciences 26 (1): 23–53. Bibcode:1998AREPS..26...23N. doi:10.1146/annurev.earth.26.1.23. [8] “HORIZONS Web-Interface for Venus (Major Body=299)" (Geophysical data). JPL Horizons On-Line [23] Strom, R. G.; Schaber, G. G.; Dawsow, D. D. Ephemeris System. 27 February 2006. Retrieved (1994). “The global resurfacing of Venus” 2010-11-28. (Using JPL Horizons you can see that on . Journal of Geophysical Research 99 (E5): 2013-Dec-08 Venus will have an apmag of −4.89) 10899–10926. Bibcode:1994JGR....9910899S. [9] Espenak, Fred (1996). “Venus: Twelve year planetary doi:10.1029/94JE00388. ephemeris, 1995–2006”. NASA Reference Publication [24] Frankel, Charles (1996). Volcanoes of the Solar System. 1349. NASA/Goddard Space Flight Center. Retrieved Cambridge University Press. ISBN 0-521-47770-0. 2006-06-20. “ [10] “Venus: Facts & Figures”. NASA. Retrieved 2007-04- [25] Batson, R.M.; Russell J. F. (18–22 March 1991). Nam- ” 12. ing the Newly Found on Venus (PDF). Pro- cedings of the Lunar and Planetary Science Conference [11] Lawrence, Pete (2005). “The Shadow of Venus”. Re- XXII. Houston, Texas. p. 65. Retrieved 2009-07-12. trieved 13 June 2012. [26] Young, C., ed. (August 1990). The Magellan Venus Ex- [12] Hashimoto, G. L.; Roos-Serote, M.; Sugita, S.; Gilmore, plorer's Guide (JPL Publication 90-24 ed.). California: M. S.; Kamp, L. W.; Carlson, R. W.; Baines, K. Jet Propulsion Laboratory. H. (2008). “ highland crust on Venus sug- gested by Galileo Near-Infrared Mapping Spectrome- [27] Davies, M. E.; Abalakin, V. K.; Bursa, M.; Lieske, J. ter data”. Journal of Geophysical Research, Plan- H.; Morando, B.; Morrison, D.; Seidelmann, P. K.; Sin- ets 113: E00B24. Bibcode:2008JGRE..11300B24H. clair, A. T.; Yallop, B.; Tjuflin, Y. S. (1994). “Re- doi:10.1029/2008JE003134. port of the IAU Working Group on Cartographic Co- ordinates and Rotational Elements of the Planets and [13] David Shiga Did Venus's ancient oceans incubate life?, Satellites”. and Dynamical As- New Scientist, 10 October 2007 tronomy 63 (2): 127. Bibcode:1996CeMDA..63..127D. doi:10.1007/BF00693410. [14] B.M. Jakosky,“Atmospheres of the Terrestrial Planets”, in Beatty, Petersen and Chaikin (eds,), The New Solar Sys- [28] “USGS Astrogeology: Rotation and pole position for the tem, 4th edition 1999, Sky Publishing Company (Boston) Sun and planets (IAU WGCCRE)". Retrieved 22 October and Cambridge University Press (Cambridge), pp. 175– 2009. 200 [29] “The Magellan Venus Explorer's Guide”. Retrieved 22 [15] “Caught in the wind from the Sun”. ESA (Venus Ex- October 2009. press). 28 November 2007. Retrieved 2008-07-12.

[16] Lopes, Rosaly M. C.; Gregg, Tracy K. P. (2004). Volcanic [30] Karttunen, Hannu; Kroger, P.; Oja, H.; Poutanen, M.; worlds: exploring the Solar System's volcanoes. Springer. , K. J. (2007). Fundamental Astronomy. Springer. p. 61. ISBN 3-540-00431-9. p. 162. ISBN 3-540-34143-9.

[17] “Atmosphere of Venus”. The Encyclopedia of Astrobi- [31] “Venus also zapped by lightning”. CNN. 29 November ology, Astronomy, and Spaceflght. Retrieved 2007-04-29. 2007. Archived from the original on 30 November 2007. Retrieved 2007-11-29. [18] Esposito, Larry W. (9 March 1984). “Sul- fur Dioxide: Episodic Injection Shows Evidence [32] Glaze, L. S. (1999).“Transport of SO2 by explosive vol- for Active Venus Volcanism”. Science 223 canism on Venus”. Journal of Geophysical Research 104 (4640): 1072–1074. Bibcode:1984Sci...223.1072E. (E8): 18899–18906. Bibcode:1999JGR...10418899G. doi:10.1126/science.223.4640.1072. PMID 17830154. doi:10.1029/1998JE000619. Retrieved 2009-01-16. Retrieved 2009-04-29. [33] Romeo, I.; Turcotte, D. L. (2009). “The [19] Bullock, Mark A.; Grinspoon, David H. (March frequency-area distribution of volcanic units on 2001). “The Recent Evolution of Climate on Venus” Venus: Implications for planetary resurfacing”. . Icarus 150 (1): 19–37. Bibcode:2001Icar..150...19B. Icarus 203 (1): 13. Bibcode:2009Icar..203...13R. doi:10.1006/icar.2000.6570. doi:10.1016/j.icarus.2009.03.036. 7.10. REFERENCES 111

[34] Shannon Hall (2014). “Active Volcanoes on Venus?". [49] Krasnopolsky, V. A.; Parshev, V. A. (1981). “Chem- Sky and Telescope. Retrieved 2014-04-02. ical composition of the atmosphere of Venus”. Nature 292 (5824): 610–613. Bibcode:1981Natur.292..610K. [35] Herrick, R. R.; Phillips, R. J. (1993). “Ef- doi:10.1038/292610a0. fects of the Venusian atmosphere on incoming me- teoroids and the impact crater population”. Icarus [50] Krasnopolsky, Vladimir A. (2006). “Chemical com- 112 (1): 253–281. Bibcode:1994Icar..112..253H. position of Venus atmosphere and clouds: Some un- doi:10.1006/icar.1994.1180. solved problems”. Planetary and Space Science 54 (13–14): 1352–1359. Bibcode:2006P&SS...54.1352K. [36] David Morrison (2003). The Planetary System. Benjamin doi:10.1016/j.pss.2006.04.019. Cummings. ISBN 0-8053-8734-X. [51] W. B., Rossow; A. D., del Genio; T., Eich- [37] Goettel, K. A.; Shields, J. A.; Decker, D. A. (16–20 ler (1990). “Cloud-tracked winds from Pio- March 1981).“Density constraints on the composition of neer Venus OCPP images” (PDF). Journal of Venus”. Proceedings of the Lunar and Planetary Science the Atmospheric Sciences 47 (17): 2053–2084. Conference. Houston, TX: Pergamon Press. pp. 1507– Bibcode:1990JAtS...47.2053R. doi:10.1175/1520- 1516. Retrieved 2009-07-12. 0469(1990)047<2053:CTWFVO>2.0.CO;2. ISSN 1520-0469. [38] Faure, Gunter; Mensing, Teresa M. (2007). Introduction to planetary science: the geological perspective. Springer [52] Normile, Dennis (7 May 2010). “Mission to probe eBook collection. Springer. p. 201. ISBN 1-4020-5233- Venus's curious winds and test for propulsion”. 2. Science 328 (5979): 677. Bibcode:2010Sci...328..677N. doi:10.1126/science.328.5979.677-a. PMID 20448159. [39] Nimmo, F. (2002). “Crustal analysis of Venus from Magellan satellite observations at Atalanta Planitia, Beta [53] Lorenz, D.; Lunine, Jonathan I.; Withers, Paul Regio, and Thetis Regio”. Geology 30 (11): 987–990. G.; McKay, Christopher P. (2001). “Titan, Mars and Bibcode:2002Geo....30..987N. doi:10.1130/0091- Earth: Entropy Production by Latitudinal Heat Trans- 7613(2002)030<0987:WDVLAM>2.0.CO;2. ISSN port” (PDF). , University of Ari- 0091-7613. zona Lunar and Planetary Laboratory. Retrieved 2007- 08-21. [40] “Venus”. Case Western Reserve University. 13 Septem- ber 2006. Retrieved 2011-12-21. [54] “Interplanetary Seasons”. NASA. Retrieved 2007-08-21. [55] Basilevsky A. T., Head J. W. (2003). “The sur- [41] Lewis, John S. (2004). Physics and Chemistry of the Solar face of Venus”. Reports on Progress in Physics System (2nd ed.). Academic Press. p. 463. ISBN 0-12- 66 (10): 1699–1734. Bibcode:2003RPPh...66.1699B. 446744-X. doi:10.1088/0034-4885/66/10/R04. [42] Henry Bortman (2004). “Was Venus Alive? 'The Signs [56] McGill G. E., Stofan E. R., Smrekar S. E. (2010).“Venus are Probably There'". space.com. Retrieved 2010-07-31. tectonics”. In T. R. Watters, R. A. Schultz. Planetary Tec- tonics. Cambridge University Press. pp. 81–120. ISBN [43] Grinspoon, David H.; Bullock, M. A. (October 2007). 978-0-521-76573-2. “Searching for Evidence of Past Oceans on Venus”. Bulletin of the American Astronomical Society 39: 540. [57] Otten, Carolyn Jones (2004). ""Heavy metal”snow on Bibcode:2007DPS....39.6109G Venus is lead sulfide”. Washington University in St Louis. Retrieved 2007-08-21. [44] Kasting, J. F. (1988). “Runaway and moist greenhouse atmospheres and the evolution of Earth and Venus”. [58] Russell, S. T.; Zhang, T. L.; Delva, M.; Magnes, Icarus 74 (3): 472–494. Bibcode:1988Icar...74..472K. W.; Strangeway, R. J.; Wei, H. Y. (2007). doi:10.1016/0019-1035(88)90116-9. PMID 11538226. “Lightning on Venus inferred from whistler- mode waves in the ionosphere”. Nature 450 [45] Venusian Cloud Colonies at the Wayback Machine (7170): 661–662. Bibcode:2007Natur.450..661R. (archived August 7, 2007) :: Astrobiology Magazine doi:10.1038/nature05930. PMID 18046401.

[46] Geoffrey A. Landis Astrobiology: The Case for Venus at [59] Hand, Eric (November 2007). “European mis- the Wayback Machine (archived August 7, 2011) sion reports from Venus”. Nature (450): 633–660. doi:10.1038/news.2007.297. [47] Cockell, C. S. (December 1999). “” . Planetary and Space Science 47 (12): 1487–1501. [60] Staff (28 November 2007). “Venus offers Earth climate Bibcode:1999P&SS...47.1487C. doi:10.1016/S0032- clues”. BBC News. Retrieved 2007-11-29. 0633(99)00036-7. [61] “ESA finds that Venus has an ozone layer too”. ESA. 6 [48] Moshkin, B. E.; Ekonomov, A. P.; Golovin Iu. M. October 2011. Retrieved 2011-12-25. (1979). “Dust on the surface of Venus”. Kos- micheskie Issledovaniia (Cosmic Research) 17: 280–285. [62] Staff (January 29, 2013). “When A Planet Behaves Like Bibcode:1979CoRe...17..232M. A Comet”. ESA. Retrieved January 31, 2013. 112 CHAPTER 7. VENUS

[63] Kramer, Miriam (January 30, 2013). “Venus Can Have [79] Correia, Alexandre C. M.; Laskar, Jacques; de Surgy, 'Comet-Like' Atmosphere”. Space.com. Retrieved Jan- Olivier Néron (May 2003). “Long-term evolution of uary 31, 2013. the spin of Venus I. theory” (PDF). Icarus 163 (1): 1–23. Bibcode:2003Icar..163....1C. doi:10.1016/S0019- [64] 1035(03)00042-3.

[65] [80] Correia, A. C. M.; Laskar, J. (2003). “Long- term evolution of the spin of Venus: II. numeri- [66] Dolginov, Nature of the Magnetic Field in the Neighbor- cal simulations” (PDF). Icarus 163 (1): 24–45. hood of Venus, COsmic Research, 1969 Bibcode:2003Icar..163...24C. doi:10.1016/S0019- 1035(03)00043-5. [67] Kivelson G. M., Russell, C. T. (1995). “Introduction to ” Space Physics . Cambridge University Press. ISBN 0- [81] , T.; Soter, S. (1969). “Atmospheric tides and 521-45714-9. the resonant rotation of Venus”. Icarus 11 (3): 356– 366. Bibcode:1969Icar...11..356G. doi:10.1016/0019- [68] Upadhyay, H. O.; Singh, R. N. (April 1995). “Cos- 1035(69)90068-2. mic ray Ionization of Lower Venus Atmosphere” . Advances in Space Research 15 (4): 99–108. [82] Shapiro, I. I.; Campbell, D. B.; de Campli, W. M. (June Bibcode:1995AdSpR..15...99U. doi:10.1016/0273- 1979).“Nonresonance rotation of Venus”. Astrophysical 1177(94)00070-H. Journal, Part 2 – Letters to the Editor 230: L123–L126. [69] Luhmann J. G., Russell C. T. (1997). J. H. Shirley and R. Bibcode:1979ApJ...230L.123S. doi:10.1086/182975 W. Fainbridge, ed. Venus: Magnetic Field and Magneto- [83] Sheppard, Scott S.; Trujillo, Chadwick A. (July 2009). sphere. Encyclopedia of Planetary Sciences (Chapman and “A survey for satellites of Venus”. Icarus 202 (1): Hall, New York). ISBN 978-1-4020-4520-2. Retrieved 12–16. arXiv:0906.2781. Bibcode:2009Icar..202...12S. 2009-06-28. doi:10.1016/j.icarus.2009.02.008. [70] Stevenson, D. J. (15 March 2003). “Planetary magnetic [84] Mikkola, S.; Brasser, R.; Wiegert, P.; Innanen, K. fields”. Earth and Planetary Science Letters 208 (1–2): 1– (July 2004). “Asteroid 2002 VE68, a quasi-satellite of 11. Bibcode:2003E&PSL.208....1S. doi:10.1016/S0012- Venus”. Monthly Notices of the Royal Astronomical So- 821X(02)01126-3. ciety 351 (3): L63. Bibcode:2004MNRAS.351L..63M. [71] Nimmo, Francis (November 2002). “Why does Venus doi:10.1111/j.1365-2966.2004.07994.x. lack a magnetic field?" (PDF). Geology 30 (11): 987– 990. Bibcode:2002Geo....30..987N. doi:10.1130/0091- [85] de la Fuente Marcos, C.; de la Fuente Marcos, R. “ 7613(2002)030<0987:WDVLAM>2.0.CO;2. ISSN (November 2012). On the dynamical evolution of ” 0091-7613. Retrieved 2009-06-28. 2002 VE68 . Monthly Notices of the Royal As- tronomical Society 427 (1): 728. arXiv:1208.4444. [72] Konopliv, A. S.; Yoder, C. F. (1996). “Venu- Bibcode:2012MNRAS.427..728D. doi:10.1111/j.1365- sian k2 tidal Love number from Magellan and PVO 2966.2012.21936.x. tracking data”. Geophysical Research Letters 23 (14): 1857–1860. Bibcode:1996GeoRL..23.1857K. [86] de la Fuente Marcos, C.; de la Fuente Marcos, doi:10.1029/96GL01589. Retrieved 2009-07-12. R. “Asteroid 2012 XE133, a transient com- panion to Venus”. Monthly Notices of the [73] Svedhem, Håkan; Titov, Dmitry V.; Taylor, Royal Astronomical Society 432 (2): 886–893. Fredric W.; Witasse, Olivier (November 2007). arXiv:1303.3705. Bibcode:2013MNRAS.432..886D. “Venus as a more Earth-like planet”. Nature 450 doi:10.1093/mnras/stt454. (7170): 629–632. Bibcode:2007Natur.450..629S. doi:10.1038/nature06432. PMID 18046393. [87] Musser, George (10 October 2006).“Double Impact May Explain Why Venus Has No Moon”. Scientific American. [74] “Venus Close Approaches to Earth as predicted by Solex Retrieved 2011-12-05. 11”. Retrieved 2009-03-19. (numbers generated by Solex) [88] Tytell, David (10 October 2006). “Why Doesn't Venus Have a Moon?". SkyandTelescope.com. Retrieved 2007- [75] “Venus”. Squyres, Steven W. Retrieved 23 May 2014. 08-03.

[76] Bakich, Michael E. (2000). The Cambridge planetary [89] Tony Flanders (25 February 2011).“See Venus in Broad handbook. Cambridge University Press. p. 50. ISBN Daylight!". Sky & Telescope. 0-521-63280-3. [90] Krystek, Lee. “Natural Identified Flying Objects”. The [77] “Could Venus be shifting gear?". European Space Unngatural Museum. Retrieved 2006-06-20. Agency. 10 February 2012. Retrieved 11 March 2015. [91] Anon.“Transit of Venus”. History. University of Central [78] “Space Topics: Compare the Planets: Mercury, Venus, Lancashire. Retrieved 14 May 2012. Earth, The Moon, and Mars”. Planetary Society. Re- trieved 2007-04-12. [92] A. – Venus transit: A last-minute guide – MSNBC 7.10. REFERENCES 113

[93] Espenak, Fred (2004). “Transits of Venus, Six Millen- [108] Russell, H. N. (1899). “The Atmosphere of nium Catalog: 2000 BCE to 4000 CE”. Transits of the Venus”. Astrophysical Journal 9: 284–299. Sun. NASA. Retrieved 2009-05-14. Bibcode:1899ApJ.....9..284R. doi:10.1086/140593.

[94] Kollerstrom, Nicholas (1998). “Horrocks and the [109] , T. (1832).“On the Rotation of Venus”. Monthly of British Astronomy”. University College London. Re- Notices of the Royal Astronomical Society 2: 78–126. trieved 11 May 2012. Bibcode:1832MNRAS...2...78H.

[95] Hornsby, T. (1771). “The quantity of the Sun's parallax, [110] Ross, F. E. (1928).“Photographs of Venus”. Astrophys- as deduced from the observations of the transit of Venus ical Journal. 68–92: 57. Bibcode:1928ApJ....68...57R. on June 3, 1769”. Philosophical Transactions of the Royal doi:10.1086/143130. Society 61 (0): 574–579. doi:10.1098/rstl.1771.0054. [111] Slipher, V. M. (1903). “A Spectrographic [96] Woolley, Richard (1969).“Captain Cook and the Transit Investigation of the Rotation Velocity of of Venus of 1769”. Notes and Records of the Royal Society Venus”. Astronomische Nachrichten 163 of London 24 (1): 19–32. doi:10.1098/rsnr.1969.0004. (3–4): 35. Bibcode:1903AN....163...35S. ISSN 0035-9149. JSTOR 530738. doi:10.1002/asna.19031630303.

[97] Baum, R. M. (2000). “The enigmatic ashen light of [112] Goldstein, R. M.; , R. L. (1963). Venus: an overview”. Journal of the British Astronomical “Rotation of Venus: Period Estimated from Association 110: 325. Bibcode:2000JBAA..110..325B. Radar Measurements”. Science 139 (3558): 910–911. Bibcode:1963Sci...139..910G. [98] Waerden, Bartel (1974). Science awakening II: the birth doi:10.1126/science.139.3558.910. PMID 17743054. of astronomy. Springer. p. 56. ISBN 90-01-93103-0. Retrieved 2011-01-10. [113] Campbell, D. B.; Dyce, R. B.; Pettengill G. H. (1976). “New radar image of Venus”. Science [99] Pliny the Elder (1991). Natural History II:36–37. trans- 193 (4258): 1123–1124. Bibcode:1976Sci...193.1123C. lated by John F. Healy. Harmondsworth, Middlesex, UK: doi:10.1126/science.193.4258.1123. PMID 17792750. Penguin. pp. 15–16. [114] Carolynn Young (August 1990). “Chapter 8, What's [100] Goldstein, Bernard R. (March 1972). “Theory and Ob- in a Name?". The Magellan Venus Explorer's Guide. servation in Medieval Astronomy”. Isis (University of NASA/JPL. Retrieved 2009-07-21. Chicago Press) 63 (1): 39–47 [44]. doi:10.1086/350839. “ [101] Sally P. Ragep (2007). “Ibn Sīnā: Abū ʿAlī al‐Ḥusayn [115] Mitchell, Don (2003). Inventing The Interplanetary ” ibn ʿAbdallāh ibn Sīnā". In Thomas Hockey. The Bi- Probe . The Soviet Exploration of Venus. Retrieved 2007- ographical Encyclopedia of Astronomers. Springer Sci- 12-27. ence+Business Media. pp. 570–572. [116] Mayer, McCullough, and Sloanaker; McCullough; [102] S. M. Razaullah Ansari (2002). History of oriental as- Sloanaker (January 1958). “Observations of tronomy: proceedings of the joint discussion-17 at the Venus at 3.15-cm Wave Length”. Astrophysi- 23rd General Assembly of the International Astronomical cal Journal (The Astrophysical Journal) 127: 1. Union, organised by the Commission 41 (History of As- Bibcode:1958ApJ...127....1M. doi:10.1086/146433. tronomy), held in Kyoto, August 25–26, 1997. Springer. [117] Jet Propulsion Laboratory (1962).“Mariner-Venus 1962 p. 137. ISBN 1-4020-0657-8. Final Project Report” (PDF). SP-59. NASA. [103] Kollerstrom, Nicholas (2004). “William Crabtree's “ Venus transit observation”. Proceedings IAU Colloquium [118] Mitchell, Don (2003). Plumbing the Atmosphere of ” No. 196, 2004. International Astronomical Union. Re- Venus . The Soviet Exploration of Venus. Retrieved trieved 10 May 2012. 2007-12-27.

[104] Palmieri, Paolo (2001).“Galileo and the discovery of the [119] Eshleman, V.; Fjeldbo, G.; Eshleman (1969). “ phases of Venus”. Journal for the History of Astronomy The atmosphere of Venus as studied with the 21 (2): 109–129. Bibcode:2001JHA....32..109P. Mariner 5 dual radio-frequency occultation exper- iment” (PDF). Radio Science. SU-SEL-69-003 [105] Fegley, B (2003). Venus (Treatise on Geochemistry ed.). (NASA) 4 (10): 879. Bibcode:1969RaSc....4..879F. Elsevier. doi:10.1029/RS004i010p00879.

[106] Marov, Mikhail Ya. (2004). D.W. Kurtz, ed. Mikhail [120]“Report on the Activities of the COSPAR Working Group Lomonosov and the discovery of the atmosphere of Venus VII”. Preliminary Report, COSPAR Twelfth Plenary during the 1761 transit. Proceedings of IAU Colloquium Meeting and Tenth International Space Science Symposium. No. 196 (Preston, U.K.: Cambridge University Press): Prague, Czechoslovakia: National Academy of Sciences. 209–219. doi:10.1017/S1743921305001390. 11–24 May 1969. p. 94.

[107] “Mikhail Vasilyevich Lomonosov”. Britannica online [121] Sagdeev, Roald; Eisenhower, Susan (28 May 2008). encyclopedia. Encyclopædia Britannica, Inc. Retrieved “United States-Soviet Space Cooperation during the Cold 2009-07-12. War”. Retrieved 2009-07-19. 114 CHAPTER 7. VENUS

[122] Mitchell, Don (2003). “First Pictures of the Surface [139] “title”. Retrieved 4 January 2015. of Venus”. The Soviet Exploration of Venus. Retrieved 2007-12-27. [140] “Solar Probe Plus: A NASA Mission to Touch the Sun” . solarprobe.jhuapl.edu. Johns Hopkins University, Ap- [123] Dunne, J.; Burgess, E. (1978). “The Voyage of Mariner plied Physics Laboratory. Retrieved 18 January 2015. 10” (PDF). SP-424. NASA. Retrieved 2009-07-12. [141]“New Frontiers missions 2009”. NASA. Retrieved 2011- [124] Colin, L.; Hall, C. (1977). “The Pioneer 12-09. Venus Program”. Space Science Reviews 20 (3): 283–306. Bibcode:1977SSRv...20..283C. [142] “Atmospheric Flight on Venus”. NASA Glenn Research doi:10.1007/BF02186467. Center Technical Reports. Retrieved 18 September 2008.

[125] Williams, David R. (6 January 2005). “Pioneer Venus [143] Feldman, M. S.; Ferrara, L. A.; Havenstein, P. L.; Project Information”. NASA Goddard Space Flight Cen- Volonte, J. E.; , P. H. (1967). Manned Venus ter. Retrieved 2009-07-19. Flyby, February 1, 1967 (PDF). Bellcomm, Inc.

[126] Mitchell, Don (2003). “Drilling into the Surface of [144] NBC Venus”. The Soviet Exploration of Venus. Retrieved [145] VENUS SAMPLE RETURN MISSIONS - A RANGE 2007-12-27. OF SCIENCE, A RANGE OF COSTS [127] Greeley, Ronald; Batson, Raymond M. (2007). Planetary [146] Chronology of Venus Exploration (NASA) Mapping. Cambridge University Press. p. 47. ISBN 978- 0-521-03373-2. Retrieved 2009-07-19. [147] The Planetary Society - An unheralded anniversary

[128] Linkin, V.; Blamont, J.; Preston, R. (1985). [148] “The Vega Venus Balloon experiment”. Bul- letin of the American Astronomical Society 17: 722. [149] Nicholson, Seth B. (1961). “The Trojan Asteroids” Bibcode:1985BAAS...17..722L. . Astronomical Society of the Pacific Leaflets 8: 239. Bibcode:1961ASPL....8..239N. [129] Sagdeev, R. Z.; Linkin, V. M.; Blamont, J. E.; Preston, R. A. (1986). “The VEGA Venus [150] Cessna, Abby. “Mythology of the Planets”. Universe Balloon Experiment”. Science 231 (4744): Today. Fraser Cain. Retrieved 19 September 2011. 1407–1408. Bibcode:1986Sci...231.1407S. “ doi:10.1126/science.231.4744.1407. JSTOR 1696342. [151] Stearn, William (May 1968). The Origin of the Male ” PMID 17748079. and Female Symbols of Biology . Taxon 11 (4): 109– 113. doi:10.2307/1217734. JSTOR 1217734. [130] Lyons, Daniel T.; Saunders, R. Stephen; Griffith, Douglas [152] Landis, Geoffrey A. (2003). “Colonization of Venus” G. (May–June 1995). “The Magellan Venus mapping . AIP Conference Proceedings 654 (1). pp. 1193–1198. mission: Aerobraking operations”. Acta Astronautica doi:10.1063/1.1541418. 35 (9–11): 669–676. Bibcode:1995AcAau..35..669L. doi:10.1016/0094-5765(95)00032-U. [131] “Magellan begins termination activities”. JPL Universe. 7.11 External links 9 September 1994. Retrieved 2009-07-30.

[132] Van Pelt, Michel (2006). Space invaders: how robotic • Venus Profile at NASA's Solar System Exploration spacecraft explore the Solar System. Springer. pp. 186– site 189. ISBN 0-387-33232-4. • Missions to Venus (Hosted by NASA) [133] Davis, Andrew M.; Holland, Heinrich D.; Turekian, Karl K. (2005). Meteorites, comets, and planets. Elsevier. p. • Gallery of Venus exploration images (Hosted by 489. ISBN 0-08-044720-1. NASA)

[134] “Timeline”. MESSENGER. Retrieved 9 February 2008. • The Soviet Exploration of Venus, Image catalog

[135] “Venus Express”. ESA Portal. European Space Agency. • Venus page at The Nine Planets Retrieved 9 February 2008. • NASA page about the Venera missions [136] G. A. Landis, “Robotic Exploration of the Surface and Atmosphere of Venus”, paper IAC-04-Q.2.A.08, Acta • Magellan mission home page Astronautica, Vol. 59, 7, 517–580 (October 2006). See animation • Pioneer Venus information from NASA

[137] “Venus Climate Orbiter “PLANET-C"". JAXA. Re- • Detailed information about transits of Venus trieved 9 February 2008. • Geody Venus, a search engine for surface features [138] “BepiColombo”. ESA Spacecraft Operations. Retrieved 9 February 2008. • Maps of Venus in NASA World Wind 7.11. EXTERNAL LINKS 115

• Chasing Venus, Observing the Transits of Venus Smithsonian Institution Libraries • Venus Crater Database Lunar and Planetary Insti- tute • Calculate/show the current phase of Venus (U.S. Naval Observatory) • Venus Astronomy Cast episode No. 50, includes full transcript. • Thorsten Dambeck: The Blazing Hell Behind the Veil, MaxPlanckResearch, 4/2009, p. 26–33 • Gray, Meghan (2009). “Venus”. Sixty Symbols. Brady Haran for the University of Nottingham.

• Venus Exploration Themes – February 2014

7.11.1 Cartographic resources

• PDS Map-a-Planet & Venus Nomenclature • Gazeteer of Planetary Nomenclature – Venus (USGS)

• Map of Venus • Movie of Venus at National Oceanic and Atmo- spheric Administration 116 CHAPTER 7. VENUS

7.12 Text and image sources, contributors, and licenses

7.12.1 Text

• Jupiter Source: http://en.wikipedia.org/wiki/Jupiter?oldid=656219186 Contributors: AxelBoldt, Magnus Manske, Brion VIBBER, Mav, Uriyan, Bryan Derksen, The Anome, -- April, Css, Ed Poor, Amillar, Andre Engels, Eclecticology, Eob, Scipius, XJaM, William , Roadrunner, SimonP, Zimriel, Fonzy, Dwheeler, Tedernst, Leandrod, Spiff, Nealmcb, Patrick, D, Michael Hardy, Tim Starling, Alan Peakall, Alighieri, Liftarn, Ixfd64, Tango, Cyde, Delirium, Iluvcapra, Minesweeper, Egil, Looxix, Ihcoyc, Mkweise, Ahoerstemeier, Stevan White, Ryan Cable, William M. Connolley, Samuelsen, Angela, Kingturtle, Ijon, Mark Foskey, Glenn, Fojxl, Poor Yorick, Kwekubo, Big iron, Med, Jeandré du Toit, Samw, JamesReyes, Lee M, Pizza Puzzle, Schneelocke, Jerryb1961, Hike395, Danbirchall, Timwi, Dino, Stone, N-true, Colipon, Malcohol, Doradus, Timc, Haukurth, Dragons flight, K1Bond007, Ed g2s, Rnbc, Traroth, Nickshanks, Bloodshed- der, Chrisjj, Jerzy, Johnleemk, Finlay McWalter, Francs2000, Hajor, Jeffq, Twang, Jason Potter, Branddobbe, Robbot, ChrisO, Korath, Chris 73, Vespristiano, RedWolf, Romanm, Naddy, Academic Challenger, Puckly, Lesonyrra, Rursus, Meelar, Bkell, Hadal, Wikibot, Qwm, Raeky, Kairos, Angilbas, Dina, Solver, Robert Happelberg, ShutterBugTrekker, Nephelin, Albatross2147, Centrx, Giftlite, Graeme Bartlett, DocWatson42, Christopher Parham, Marnanel, Djinn112, Awolf002, Jyril, Jackyfung7, Harp, Wolfkeeper, Cobaltbluetony, Lupin, Ferkelparade, Bradeos Graphon, Everyking, , Curps, Michael Devore, JamesHoadley, Wikibob, Jdavidb, Rick Block, Brendan- Ryan, Solipsist, Iceberg3k, Python eggs, DÅ‚ugosz, Bobblewik, Edcolins, Mateuszica, Wmahan, ChicXulub, StuartH, Utcursch, Patteroast, Slavering.dog, Zeimusu, ConradPino, GeneralPatton, Quadell, Antandrus, The Singing Badger, HorsePunchKid, Jodamiller, Beland, Jo- Jan, MisfitToys, Vanished user 1234567890, Kusunose, FelineAvenger, Khaosworks, Rdsmith4, RetiredUser2, SAMAS, Icairns, Karl- Henner, Sarphram, Gscshoyru, JulieADriver, Urhixidur, Edsanville, Joyous!, Expatkiwi, Muijz, Subsume, Deglr6328, Mtnerd, Adashiel, Eisnel, Bluemask, Mike Rosoft, Freakofnurture, N328KF, Venu62, DanielCD, Ultratomio, Bornintheguz, Moverton, Discospinster, Rich Farmbrough, Guanabot, Pjacobi, Vsmith, Pie4all88, ArnoldReinhold, Autiger, Ponder, Mjpieters, El Shaday, Arthur Holland, Wadewitz, MuDavid, Quistnix, Uppland, SpookyMulder, Bender235, ESkog, Kbh3rd, Kjoonlee, Neko-chan, Violetriga, Nabla, Brian0918, RJHall, Karmafist, El C, Mulder1982, Bletch, Joanjoc, Kwamikagami, Kross, Worldtraveller, Shanes, Tom, C1k3, Remember, Art LaPella, Deanos, Femto, CDN99, Causa sui, Devil Master, Bobo192, Dralwik, NetBot, Hurricane111, Smalljim, Dreish, Flxmghvgvk, Cohesion, Larsie, Vystrix Nexoth, Azure Haights, BillCook, MPerel, Sam Korn, (aeropagitica), Krellis, Pharos, Hagerman, Supersexyspacemonkey, Phy- zome, TobyRush, Jcrocker, Knucmo2, Jumbuck, Storm Rider, Danski14, Bob rulz, Qwe, Nik42, Mo0, Andrewpmk, AzaToth, Lightdark- ness, RoySmith, Mlm42, Hu, Bart133, Snowolf, Wtmitchell, Dhartung, Schapel, Hadlock, Knowledge Seeker, Yuckfoo, Suruena, Evil Monkey, Tony Sidaway, Amorymeltzer, Alfvaen, Sciurinæ, Inge-Lyubov, LFaraone, Gortu, Gene Nygaard, Paraphelion, Ringbang, Hen- ryLi, Kitch, Dan100, Antifamilymang, Harvestdancer, Adrian.benko, Oleg Alexandrov, Tariqabjotu, Zephiris, Feezo, Siafu, Kfitzner, WilliamKF, Novacatz, Haverton, Bacteria, Richard Arthur Norton (1958- ), Sanjaymjoshi, Rorschach, OwenX, Woohookitty, Tiger- Shark, PoccilScript, Daniel Case, Ugo, Uncle G, Borb, HisHighness420, TomTheHand, BillC, Benbest, Pol098, Bricktop, Kristaga, Dun- can.france, MONGO, Mpatel, Gayle crockett, Pi@k, Will.i.am, Thesquire, Bluemoose, Wtfunkymonkey, Sengkang, GregorB, Eyreland, Waldir, Wayward, とある白い猫, Alec Connors, Smartech, Wisq, Gavino, Aarghdvaark, Ashmoo, Graham87, Marskell, Magister Math- ematicae, MC MasterChef, FreplySpang, Hrothgar15, Nlsanand, Pentawing, Search4Lancer, Canderson7, Drbogdan, Sjakkalle, Rjwilmsi, Tim!, Koavf, Panoptical, Commander, Urbane Legend, Bob A, Bill37212, Stardust8212, Captmondo, Tawker, Mike s, SMC, Mike Peel, Justin Hirsh, Kazrak, Crazynas, Ligulem, SeanMack, Bubba73, Brighterorange, Yug, The wub, Bhadani, GregAsche, Sango123, Lotu, Yamamoto Ichiro, FayssalF, Titoxd, Nikson-t, SchuminWeb, RobertG, Old Moonraker, Flydpnkrtn, Musical Linguist, Nihiltres, Harmil, GT, RexNL, Gurch, RobyWayne, Vayne, Arctic.gnome, DannyZ, Str1977, TeaDrinker, Consumed Crustacean, Supersaiyanplough, Srl- effler, Le Anh-Huy, Imnotminkus, King of Hearts, Urzeitlich, Chobot, Spasemunki, Digitalme, Gwernol, Algebraist, Thumbtacks, Dio- genes00, YurikBot, Wavelength, TexasAndroid, Spacepotato, Vedranf, Reverendgraham, Neitherday, Sceptre, Hairy Dude, Deeptrivia, Huw Powell, Jimp, Gene.arboit, Kymacpherson, RussBot, Sarranduin, Sillybilly, TheDoober, Splash, SpuriousQ, Fabricationary, Zelmer- szoetrop, Stephenb, Lavenderbunny, Matt.lohkamp, Wimt, NawlinWiki, Jessesaurus, Wiki alf, BGManofID, Aeusoes1, Test-tools, Jaxl, Agent003, Terfili, Journalist, Stephen e nelson, Dureo, Bmdavll, Cleared as filed, Irishguy, Anetode, Brandon, Cholmes75, CPColin, Chal7ds, Rmky87, Moe Epsilon, Tony1, Alex43223, Harishsubramanian, The Peacemaker, Syrthiss, Bota47, Jessemerriman, Hosterweis, Tachyon01, Milkyeyes, Brisvegas, Martinwilke1980, Yasth, Dna-webmaster, Nick123, Wknight94, Ms2ger, Robost, FF2010, 21655, Key- stone32, PTSE, Chesnok, Kandrey89, Ageekgal, Pb30, Canley, BorgQueen, Petri Krohn, Alias Flood, AliasHandler, Peter, Hurricane Devon, Jolb, HereToHelp, Emc2, ArielGold, Calilasseia, Junglecat, Banus, RG2, KNHaw, Iago , Draicone, Serendipodous, DVD R W, Brentt, Caponer, The Wookieepedian, Deuar, Sardanaphalus, Attilios, KnightRider, Jas pierce, A bit iffy, SmackBot, Aths, Zork- , Doktor, KnowledgeOfSelf, Martin.Budden, Lagalag, Primetime, Jim62sch, Vald, Bwilliams, Jagged 85, Davewild, ScaldingHot- Soup, Verne Equinox, MarcusPan, Jedikaiti, EncycloPetey, Kintetsubuffalo, Edgar181, Galloglass, Markeer, Gaff, Xaosflux, Pinpoint23, Cuddlyopedia, Aksi great, Peter Isotalo, Hmains, Skizzik, ERcheck, JAn Dudík, Tv316, Saros136, Amatulic, Chris the speller, Endroit, Bluebot, Ciacchi, Cush, Derrickjohnson2, Vandago, Keegan, Persian Poet Gal, Oli Filth, Jon513, Pylori, Anchoress, MalafayaBot, Hi- bernian, WeniWidiWiki, Ikiroid, Ctbolt, Ned Scott, Roy Al Blue, Sbharris, Colonies Chris, Gracenotes, Mikker, Gyrobo, Spride, Zsinj, E946, Can't sleep, clown will eat me, Ajaxkroon, Aerobird, Tamfang, V1adis1av, Mrwuggs, The Placebo Effect, Racklever, OOODDD, NLightmare, Astrobhadauria, Darthgriz98, Wikipedia brown, Chiao, Arod14, Pnkrockr, Aces lead, Addshore, Edivorce, Celarnor, Ctifum- dope, Notovny, Wince01, Flyguy649, Iapetus, Hopquick, Nakon, Ninjers, Blake-, SnappingTurtle, RandomP, Alexander110, Mini-Geek, Mikaly, Weregerbil, Polonium, Only, Hammer1980, Glenn Browne, Zonk43, BiggKwell, Ericl, Oceanh, Kalathalan, Mystaker1, Ligulem- bot, DDima, Vina-iwbot, Samuel Sol, Bejnar, Pilotguy, Kukini, Sarfa, Tredanse, SashatoBot, Nathanael Bar-Aur L., Esrever, Erimus, Harryboyles, Rklawton, Kuru, Richard L. Peterson, John, Twohlrab3, AmiDaniel, WhiteCat, Scientizzle, Vgy7ujm, Ascend, Heimstern, Caylan12-06, Soumyasch, Breno, Linnell, Kreuzfeld, JorisvS, Temple, Evan Robidoux, GVP Webmaster, Mgiganteus1, Aleenf1, Iron- Gargoyle, Jess Mars, Ckatz, The Man in Question, RandomCritic, Il consiglieri, A. Parrot, Werdan7, Noah Salzman, Suraj vas, Xiaphias, Rwboa22, Cajolingwilhelm, Waggers, SandyGeorgia, Anonymous anonymous, Ryulong, Ephant, Big Smooth, RichardF, Elb2000, Jose77, NuncAutNunquam, Politepunk, Sonic3KMaster, Michaelbusch, Masoninman, LeyteWolfer, Joseph Solis in Australia, Newone, Pega- sus1138, Pokemega32, GDallimore, Fsotrain09, Espi, Abdul Muhib, Thomasph, Civil Engineer III, Peteweez, Tawkerbot2, Dlohcierekim, Daniel5127, Ouishoebean, Acom, Pete g1, Poolkris, Orangutan, Samnuva, MightyWarrior, Cavac, JForget, InvisibleK, CmdrObot, Deon, Ale jrb, Wafulz, Scohoust, Funion987, Picaroon, S035593, Zureks, CWY2190, Ruslik0, GHe, Benwildeboer, DeepSkyFrontier, Dgw, Dr. Eggman3, SEJohnston, Skoch3, Lazulilasher, Logical2u, Avillia, Casper2k3, Ken Gallager, Charlie Huggard, Ufviper, Icek, Sopo- foric, Cydebot, Nbound, Jjeffrey, ChristTrekker, Reywas92, Treybien, Steel, SyntaxError55, Sruav, Gogo Dodo, Tom.freeman, An- thonyhcole, Flowerpotman, Fredo1983, ST47, Dark-hooded smoker, Scott14, Fifo, Michael C Price, Tawkerbot4, DumbBOT, Inking- ton, After Midnight, Omicronpersei8, Robert.Allen, Daniel Olsen, Gimmetrow, FrancoGG, EnglishEfternamn, Rjm656s, TiroDeAethra, DJBullfish, Thijs!bot, Epbr123, Oreo man, Mikebuer, Opabinia regalis, Factmon, Hit bull, win steak, LeeG, Aster2, RolfSander, Ker- aunos, 24fan24, Headbomb, Wongizzle06, John254, Tapir Terrific, Bad Astronomer, Neil916, I do not exist, Ctu2485, Astrobiologist, 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 117

Lars Lindberg Christensen, Davidhorman, Pahoeho, GregMinton, Prof info, Lithpiperpilot, BlytheG, Escarbot, KrakatoaKatie, AntiVan- dalBot, Majorly, Abu-Fool Danyal ibn Amir al-Makhiri, Luna Santin, Crabula, Opelio, EarthPerson, Benjaburns, Quintote, Autocracy, 17Drew, Jj137, Zappernapper, Dr. Submillimeter, Gdo01, Gregorof, Once in a , SkoreKeep, Fireice, Storkk, Myanw, Kaini, Nicodème, PresN, Joehall45, Zombiepirate 13, IrishFBall32, JAnDbot, Narssarssuaq, Jirachi, Milonica, Deflective, MER-C, ElComandan- teChe, CosineKitty, Something14, IanOsgood, Bigscarymike, Andonic, Noobeditor, Hut 8.5, 100110100, Tstrobaugh, Hardee67, Kirrages, Rothorpe, .anacondabot, Acroterion, FaerieInGrey, Ruthfulbarbarity, WolfmanSF, Murgh, Parsecboy, Bongwarrior, VoABot II, Miguel- Munoz, MartinDK, Smoke., Transcendence, Xn4, Lubumbashi, Hasek is the best, SYLFan74, -Kerplunk-, CattleGirl, Mbc362, Xkcd, -Bigdan201, Violentbob, Rami R, Jespinos, Confiteordeo, BillDeanCarter, Jim Douglas, Nyttend, Rich257, Kukan ,باسم ,Selfishjeans otas, Cyktsui, Ttpedia, BatteryIncluded, ArthurWeasley, Notamisfit, Adrian J. Hunter, Hamiltonstone, Allstarecho, Involutaryhaxor, Lin- day51, P.B. Pilhet, Jc1346729, Spellmaster, Shijualex, Dmehring, Glen, DerHexer, Wdflake, Megalodon99, Khalid Mahmood, Kheider, Darkside5001, NatureA16, Gjd001, B9 hummingbird hovering, Hdt83, MartinBot, BetBot, Arjun01, Poeloq, Eshafto, Rettetast, Mschel, Pallasathena, CommonsDelinker, AlexiusHoratius, Bryanadamtan, WelshMatt, Lilac Soul, Nerablade, Omega34, Exarion, Huzzlet the bot, Watch37264, Leon math, DrKiernan, Trusilver, GreenRunner0, Rgoodermote, EscapingLife, AAA!, Ali, JamesR, Sp3000, Lizrael, Abby, Hans Dunkelberg, Nigholith, Teacher123, Eliz81, Extransit, Tdadamemd, OfficeGirl, KatyNicholslikesnosehair, Gzkn, Zipzipzip, Frum- merThanThou, Gman124, Lunokhod, Jackj08, Jeepday, Oddgunner, Gurchzilla, Squidlegs number one, Pyrospirit, Ravenicus451, Chem- icalrubber, NewEnglandYankee, Sd31415, SmilesALot, Milchild05, SJP, IsaacMcHelicopter, W3stfa11, Tanaats, Shoessss, Cbddough- boy, Sunderland06, Cometstyles, Craiglynn666, U.S.A.U.S.A.U.S.A., C.m.jones, Aramjm, Elenseel, Yomama 007, Homo logos, w123, Jcamts, Rvwedd, Piepoop, Sgeureka, Xiahou, Angel123123, ThePointblank, Kelevra88, Erasmosis, Spellcast, Idarin, Maridius, Guy14, Fainites, Jochem Atteveld, Lights, Deor, King Lopez, VolkovBot, CWii, Midoriko, Jlaramee, Tesscass, Alexandria, AlnoktaBOT, Toddles29, Katydidit, Dextrose, Philip Trueman, Law Lord, TXiKiBoT, Quackdave, Dwmr, Ezer22, Rightfully in First Place, Differo, Reptile5000, Secret agent with brown hat, Wedge1, Qaletaqa, Caster23, GDonato, Dchall1, Jorgezoltan, Sean D Martin, DJFrankie2468, Qxz, Lradrama, cornix, MasterSci, Phoxtrot, Danlikebooks, 06monkey, JhsBot, Don4of4, Cool moe dee 345, Mkolp58, Broad- bot, Abdullais4u, Fbs. 13, Seb az86556, Mannafredo, UnitedStatesian, Myden, Cremepuff222, Xyragx, Onore Baka Sama, Moppt, Trueemo, CarbonUnit2, Conalmal, CO, RR1991, NateLevine, Dark Wolf101, SwahilidR, Arfur20, SheffieldSteel, Pious7, Billinghurst, Ar-wiki, Brainmuncher, Alecdude, Viktor-viking, Synthebot, Shrinkbcoz, Rbinet, Benandersen, Burntsauce, Songtag, Kedeja, Sampaultan, Gspinoza, Brianga, Ricegator, Alcmaeonid, Hinomaru kun, Whalequeen, Smerlinare, Jordanjhd, AlleborgoBot, Drseal, Srogue, Hero- joe1000, Charvez12, Vsst, NHRHS2010, EmxBot, Tedstryk, D. Recorder, Demmy, Jrod2, SieBot, Kfc1864, TJRC, Jim77742, PlanetStar, Scarian, Oldag07, Gerakibot, Viskonsas, Caltas, Triwbe, Bladesonic, Jacob102193, Yulu, Purbo T, Eaomatrix, Keilana, Lonewolf1654, Interchange88, Aaaxlp, Aillema, Jonathan Barrett, Jakeis1, Radon210, Oysterguitarist, Editore99, Oda , Chris Gottschalk, I need a stupid username, Gublefink, Dangerousnerd, Paolo.dL, JSpung, Wombatcat, Jakmak123, Calex1, Mackojee, Tenjhotenge, Oxymoron83, Ddxc, Smilesfozwood, Conner40, Lukelpv5853, Mattl2001, Nk.sheridan, Gangsterls, KPH2293, Nerd123456789, Asdarknessfadesaway, You blocked me, Steven Zhang, Lightmouse, Ehousehay, ThAtSo, AustinTarzia, Murlough23, RSStockdale, Lopp777, BenoniBot, Dtbrock, Scott55555, Dsmith7707, Laddog, I'm a sockpuppet, Ttime27, SOLOMON92, Sertafied, Paddywikman, Dermot92, Vandalismhater789, Nagolkid2, Poopmaster01, Poopmaster03, ChrisWallis, Slavkovranes29, Barks0, Maelgwnbot, FtLulz, LonelyMarble, Anchor Link Bot, Jons63, Into The Fray, AndySmith84, C0nanPayne, Uscchic735, Freewayguy, Athenean, Jdmmxbth, SallyForth123, Sagredo, Loren.wilton, ClueBot, Mariordo, PipepBot, Matdrodes, Postmortemjapan, Starkiller88, Wercloud, Jan1nad, T.Neo, UserDoe, Cp111, Bobisbob, Mis- bah Ismailjee, Aria1561, Stargazer 7000, SuperHamster, Wikidog783, Ajczdabomb, I am the antichrist, Donthackppl, Iminnocent0, Danie2dixon, Neverquick, Knezzoran, DigitalAttorney, DragonBot, Ale221, Excirial, -Midorihana-, M4gnum0n, Breakdancingninja, War guy234, Monobi, PixelBot, Deathgiggity, Supabanakid, Thispagedoesown, Darthnat, Commdor, Sun Creator, P-griffin150, Rideauposse, JINN66, Ice Cold Beer, Cenarium, Aurora2698, PhySusie, Blitz123, Poisonink, Mtsmallwood, Dekisugi, Sophixer, Cyclopaedia, BOTarate, Kakofonous, TomJMcDonald, Aprock, Sparta300xps, CowAteMe, Thingg, Aitias, TR 667, R98563256, Superericmoore, Xplayabyname, Varha, Qwfp, Tylerdfreeze11, Isidoros47, Nickman339, Must eat worms, Chr334, BodhisattvaBot, Swift as an Eagle, Snorks1234, Mat- trave, Demonminde, Jupiter Rapist, Rreagan007, Poodudeman, Thetruth77, Eiaschool, Ericcool99, Yoshi thomas, Veenluk, Noctibus, NHJG, JinJian, Qwertyuiop click, Dinosaursrule42, Junox, JCDenton2052, Kurtus77, Homrsmpsnrulz, Miagirljmw14, GiLLyDaGuN, Jadtnr1, Apocalypse2011, Kbdankbot, Sis143, Angrome9, Ryan-McCulloch, Hawkania, Roentgenium111, Lagus970, DOI bot, Ele- ment16, Fgnievinski, Bugmenot1984, Punkprincess082307, Savage84, DrSamba, Heremod, Proxima Centauri, LaaknorBot, CarsracBot, Favonian, ChenzwBot, LinkFA-Bot, Xev lexx, R.H.H.L.B., 84user, Numbo3-bot, F Notebook, Craigsjones, Lightbot, Ettrig, Windward1, Koltentb, Yobot, Ptbotgourou, Mech Aaron, TaBOT-zerem, Castagna, KamikazeBot, Рөстәм Нурыев, Ayrton Prost, The Flying Spaghetti Monster, AnomieBOT, Archon 2488, Galoubet, Materialscientist, Ckruschke, The High Fin Sperm Whale, Citation bot, Nunna003, Xqbot, Timir2, Intelati, A455bcd9, TechBot, Lionboy-Renae, Smk65536, Gospodar svemira, Mlpearc, Srich32977, Woodstock aeb, Nayvik, Her- nanQB, RibotBOT, Charvest, Shadowjams, Datakid1100, Confront, Fotaun, Armchairslugger, Thehelpfulbot, FrescoBot, Dogzrule101, LucienBOT, Paine Ellsworth, Tobby72, Io Herodotus, Lookang, Drongou, KokkaShinto, Craig Pemberton, Dhtwiki, Ivoras, Citation bot 1, DigbyDalton, Kalisitahi, Wiklol, Pinethicket, HRoestBot, Tanweer Morshed, Tom.Reding, RedBot, Lars Washington, Thinking of Eng- land, Pink fuzzy slippers, Djwebb1969, VAP+VYK, FoxBot, Double sharp, TobeBot, Sweet xx, DixonDBot, Vrenator, Begoon, Luvenno, Tbhotch, RjwilmsiBot, Ripchip Bot, Elitropia, DASHBot, EmausBot, WikitanvirBot, Qurq, AmericanLeMans, Racerx11, Gwillhickers, HarDNox, Kkkdddiii, ZéroBot, Josve05a, A2soup, Nicolas Eynaud, AvicAWB, Hevron1998, Aeonx, Demomoer, Cline92, Мл.научный сотрудник, L Kensington, Andy 3015, Sailsbystars, Ontyx, Grv619, StephenKingFan100, K Alan Drummond, ChuispastonBot, Knochen, ChiZeroOne, Terra Novus, ThomasElwood, Karthikrrd, Mjbmrbot, Fjörgynn, ClueBot NG, Xession, Kamek98, Lanthanum-138, Fri- etjes, Dalekcan, Pollying, Pluma, Megalobingosaurus, Diyar se, Bibcode Bot, Supergamer101, RZuljani, BG19bot, Pine, WikiPeterD, MKar, Hz.tiang, Odarcan, AvocatoBot, ERJANIK, Cadiomals, Mdy66, PrintedScholar, Harizotoh9, Tycho Magnetic Anomaly-1, Zedshort, Ubiquinoid, Nbrothers, Oscar45596524, BattyBot, ChrisGualtieri, Asisman, Waylesange, Dexbot, RazrRekr201, Blobbie244, Anderson, Reatlas, Joeinwiki, Anastronomer, Lindenhurst Liberty, Seppi333, Kogge, AfadsBad, Artificial123, Samatict, Exoplanetaryscience, Can- cina5645, Ethically Yours, Monkbot, Koolman642, Spiderjerky, Py1905py, Tetra quark, Anand2202, TheWhistleGag and Anonymous: 1610

• Mars Source: http://en.wikipedia.org/wiki/Mars?oldid=656088329 Contributors: Joao, Peter Winnberg, Dreamyshade, Lee Daniel Crocker, Brion VIBBER, Eloquence, Mav, Bryan Derksen, Robert Merkel, Zundark, Berek, Tarquin, Stephen Gilbert, Jeronimo, -- April, Dave McKee, Ed Poor, Mirwin, Eob, Danny, XJaM, JeLuF, Rmhermen, Christian List, MadSurgeon, Miguel, Roadrunner, SimonP, Zoe, Waveguy, Arj, Arno, Hephaestos, Olivier, Xlation, Mbecker, Fransvannes, Spiff, Edward, Patrick, D, Michael Hardy, Oliver Pereira, Lexor, David Martland, Gabbe, Ixfd64, Sannse, Dewe, Shoaler, GTBacchus, Minesweeper, Egil, Looxix, Ihcoyc, Ahoerstemeier, An- ders Feder, Stevenj, William M. Connolley, Zouhair, Plop, Notheruser, Mark Foskey, Setu, Александър, Salsa Shark, Cyan, Poor Yorick, Netsnipe, Susurrus, Kwekubo, Rotem Dan, Evercat, Astudent, Ghewgill, Samuel, BRG, Epo, Schneelocke, Iseeaboar, Hike395, RodC, Adam Bishop, Vanished user 5zariu3jisj0j4irj, Timwi, JonMoore, Wikiborg, RickK, Reddi, Stone, Denni, Audin, Doradus, Haukurth, Bir- kett, Tpbradbury, Dragons flight, Morwen, Populus, Omegatron, Ed g2s, Rnbc, Babbler, Samsara, Thue, Xaven, Traroth, Nickshanks, 118 CHAPTER 7. VENUS

Sandman, Bloodshedder, Scott Sanchez, Lmov, Skood, Wetman, Chrisjj, Secretlondon, Jerzy, Flockmeal, Liam, Jni, Twang, Donar- reiskoffer, Branddobbe, MattSal, Robbot, Zandperl, Alrasheedan, Baldhur, Nurg, Romanm, Naddy, Mikepelley, PedroPVZ, Rursus, TM- Lutas, Mlaine, Roscoe x, Halibutt, Caknuck, Bkell, Hadal, UtherSRG, Borislav, Vikingstad, Anthony, SoLando, BovineBeast, Robert Happelberg, ShutterBugTrekker, Nephelin, Alexwcovington, Centrx, Giftlite, Reubenbarton, DocWatson42, MPF, Marnanel, Djinn112, Awolf002, Jyril, Laudaka, YanA, Sj, TOttenville8, Yuri koval, Harp, Wolfkeeper, Ævar Arnfjörð Bjarmason, Levin, Lupin, Ferkelpa- rade, Rbs, Herbee, Angmering, 0x6D667061, Braaropolis, Bradeos Graphon, Wwoods, Anton Mravcek, Everyking, Perl, Curps, Jonathan O'Donnell, Michael Devore, Henry Flower, Wikibob, Joe Kress, Cantus, Semorrison, Revth, Erdal Ronahi, Guanaco, Beowulf king, Mboverload, Darin, Matt Crypto, Python eggs, Bobblewik, Mateuszica, John , Wmahan, OldakQuill, Stevietheman, ChicXulub, Chowbok, JeffyJeffyMan2004, Latitudinarian, Kums, Pcarbonn, Ran, Antandrus, The Singing Badger, HorsePunchKid, Beland, Eroica, MisfitToys, Piotrus, Scottperry, Vanished user 1234567890, Kaldari, Nils, Josquius, Rdsmith4, Oneiros, Kesac, Wikster E, Latitude0116, Kevin B12, Tomruen, CharlieZeb, Kuralyov, Icairns, Gscshoyru, Nickptar, B.d.mills, Bradlegar, Neutrality, Urhixidur, Edsanville, TJS- woboda, Jafro, Ukexpat, Klemen Kocjancic, Trilobite, Tonik, M1ss1ontomars2k4, Adashiel, Lacrimosus, MaikSchreiber, Mike Rosoft, Mr Bound, N328KF, Poccil, DanielCD, JTN, Ultratomio, Dablaze, Simmie, Jkl, Discospinster, Solitude, Rich Farmbrough, Guanabot, GrantHenninger, Rameses, Vsmith, Edibobb, Florian Blaschke, MeltBanana, Ponder, Ibagli, Mani1, MuDavid, Aardark, Paul August, Robertbowerman, SpookyMulder, Bg, Bender235, ESkog, NeilTarrant, Calamarain, Wild Bill, Kbh3rd, Neko-chan, Evice, Brian0918, Mattingly23, RJHall, JamesR1701E, CanisRufus, Omnibus, JustPhil, MBisanz, El C, Huntster, Kwamikagami, Gnomz007, Worldtrav- eller, Aude, Shanes, Joaopais, Tom, Art LaPella, RoyBoy, Nickj, Mark R Johnson, Femto, Wareh, Dalf, Causa sui, Noren, Bobo192, -TheProject, Scen ,לערי ריינהארט ,NetBot, Apollo2011, Olve Utne, Viriditas, AllyUnion, Phidauex, Mpvdm, Jojit fb, Pierre2012, Nk toni, Kpbtm, Vorlon, MPerel, Sam Korn, Gsklee, Shikasta, Perceval, HasharBot, Jumbuck, Stephen G. Brown, Bob rulz, Lyle, Junior aspirin, Eleland, Keenan Pepper, Andrewpmk, Plumbago, Andrew Gray, A.T.M.Schipperijn, Riana, Yamla, Lectonar, MarkGallagher, Scarecroe, Lightdarkness, RoySmith, TommyBoy, Mlm42, Hu, Malo, VladimirKorablin, Bart133, Metron4, Snowolf, BanyanTree, Mm- baldwin, KingTT, Suruena, Katepaull, Evil Monkey, Aaarrrggh, Tedp, Amorymeltzer, Sciurinæ, IMeowbot, Inge-Lyubov, Cmapm, Kusma, Ianblair23, Itsmine, Paolorausch, Gene Nygaard, Alai, Iustinus, Avram Fawcett, Kazvorpal, Kitch, Ceyockey, BerserkerBen, RyanGerbil10, Tariqabjotu, Siafu, Gmaxwell, Newnoise, WilliamKF, Plateau99, Bacteria, Kelly Martin, Woohookitty, Lost.goblin, Masterjamie, LOL, Asteron, PoccilScript, Volcanopele, Uncle G, Benhocking, HisHighness420, BillC, Jacobolus, Matey, Bigfrozenhead, Benbest, Ikescs, Ma Baker, Pol098, ^demon, JeremyA, Kristaga, MONGO, Xaliqen, Bamf, Pi@k, Astrophil, Sengkang, Someone42, GregorB, BlaiseFEgan, Eyreland, Mb1000, CharlesC, Wayward, DanHobley, Teemu Leisti, Lazareth, Giantsrule, Gerbrant, Emerson7, Forezt, Ashmoo, Gra- ham87, Marskell, WBardwin, Magister Mathematicae, BD2412, Li-sung, FreplySpang, JIP, Seyon, MasterPlan, AnimAlu, Pentawing, Phasmatis, Drbogdan, Sjakkalle, Rjwilmsi, Koavf, Саша Стефановић, Ittiz, Loginnow, Vary, Hjb26, Stardust8212, Bruce1ee, Captain Disdain, Coyo, MZMcBride, Tawker, Mike s, SMC, Mike Peel, Nneonneo, Kazrak, Crazynas, Cww, Bubba73, Brighterorange, Bhadani, Sango123, Dbigwood, Yamamoto Ichiro, Ghalas, Marsbound2024, FayssalF, RCBot, FlaBot, Figs, Ian Pitchford, RobertG, Black Sword, Flydpnkrtn, Latka, Crazycomputers, JiFish, MacRusgail, SouthernNights, Chanting Fox, Itinerant1, Themanwithoutapast, RexNL, Davide- Andrea, BjKa, Arctic.gnome, DannyZ, KFP, TeaDrinker, Carrionluggage, Goudzovski, Alphachimp, Srleffler, Johhny-turbo, Le Anh-Huy, Gareth E Kegg, Bedford, Bschlee, MoRsE, Nomadtales, Chobot, Metropolitan90, Mordicai, Gwernol, Rollie, EamonnPKeane, Slasher600, Satanael, YurikBot, Wavelength, Borgx, TexasAndroid, Liamscanlan, Eraserhead1, Deeptrivia, Chris Mounce, Brandmeister (old), Jeffthe- jiff, RussBot, Fabartus, Sillybilly, NorCalHistory, Witan, Zafiroblue05, Mrboh, Jengelh, Bergsten, BlongerBros, Yosef1987, CanadianCae- sar, JimmyTheWig, RadioFan, Hydrargyrum, Van der Hoorn, Chensiyuan, Stephenb, Rintrah, Polluxian, Jeffaenima, Gaius Cornelius, Ky- orosuke, Wimt, Ugur Basak, TopAce, Daveswagon, Shanel, NawlinWiki, A314268, Shreshth91, SEWilcoBot, Wiki alf, BGManofID, Bjf, Aeusoes1, Janke, Test-tools, Grafen, Exir Kamalabadi, Agent003, Chunky Rice, Smowton, Taco325i, Joelr31, Journalist, Adamwankenobi, Ydris, Nick, Wonglokking, Ghostreveries, Jimmyre, CecilWard, ThrashedParanoid, Blu Aardvark, E rulez, Dfgarcia, PhilipC, Number 57, Moe Epsilon, Misza13, Grafikm fr, Semperf, Tony1, Kwnd, Gadget850, DeadEyeArrow, Bota47, Darkfred, Milkyeyes, Martinwilke1980, Tonywalton, Wknight94, AjaxSmack, Noosfractal, Tetracube, FF2010, American2, Capt Jim, Calaschysm, Jason Donaldson, Lt-wiki- bot, Encephalon, Kandrey89, Closedmouth, Jwissick, Fang Aili, Moogsi, Pb30, Shirishag75, Bigboss sb, Reyk, GraemeL, Aeon1006, JoanneB, Kier07, , Peter, Hurricane Devon, Geoffrey.landis, HereToHelp, ArielGold, Thefirstdude02, Nixer, Cromag, RunOrDie, Purples, Lyle zapato, Kungfuadam, RG2, Pnazemi, Renegade54, JDspeeder1, NeilN, Justice League 05, DearPrudence, Philip Stevens, GrinBot, Iago Dali, SkerHawx, Serendipodous, Elliskev, Nick-D, Deuar, Sardanaphalus, Sintonak.X, Crystallina, KnightRider, Smack- Bot, ZorkFox, Aim Here, Ttzz, Xkoalax, Jjbb, Bobet, TheFloppyOne, Zanter, Prodego, KnowledgeOfSelf, Martin.Budden, David.Mestel, Roofus, Jacek Kendysz, Jagged 85, Nickst, RedSpruce, EncycloPetey, Delldot, Eskimbot, ProveIt, Kintetsubuffalo, ComaDivine, Jpv- inall, Flamarande, Edgar181, Orpheo, Aksi great, Onsly, PeterSymonds, Gilliam, Ohnoitsjamie, Hmains, Skizzik, Universal1300, Law, Andy M. Wang, Vechs, Oneismany, Saros136, Ebill, Westsider, Happywaffle, Bluebot, Keegan, Geneb1955, Gaiacarra, CKA3KA, Persian Poet Gal, Iain., Raymond arritt, Kunalmehta, Anchoress, MalafayaBot, Silly rabbit, SchfiftyThree, Hibernian, Rosamelia- martinez, Bob the ducq, FTAAPJE, Dlohcierekim's sock, J. Spencer, E9, Saturn7, NeoNerd, DHN-bot, Leoniceno, D T G, Thered- [email protected], Mkamensek, Mcstxc7, Arsonal, LTH, Firetrap9254, A. B., Yanksox, Pastapuss, Royboycrashfan, WDGraham, Zsinj, Kotra, Can't sleep, clown will eat me, Scott3, Shalom Yechiel, Tamfang, Jefffire, Scray, HoodedMan, Njál, Mrwuggs, OrphanBot, Jen- nica, MJCdetroit, Astrobhadauria, Darthgriz98, TheKMan, Cfassett, Starexplorer, 's Bulldog, Aces lead, Seattlenow, Andy120290, Addshore, Whpq, SundarBot, Bummerdude62, Jmlk17, Lansey, Aldaron, Krich, Pondster123, Answerthis, Flyguy649, Iapetus, Down- wards, Nibuod, Nakon, Will2710, Red1, Aelffin, Dreadstar, Nutschig, RandomP, Thegraham, John oh, Crd721, The PIPE, Minority2005, DMacks, Bob Castle, Drc79, Zonk43, Maelnuneb, Kendrick7, Ericl, A5b, LeoNomis, Suthers, Kukini, BlackTerror, SashatoBot, CFLeon, Lester, Harryboyles, Sophia, Kuru, John, T g7, AmiDaniel, Bernard192, Ninjagecko, Bilboon, Vgy7ujm, Millionsofleeches, Korean al- pha for knowledge, Soumyasch, Breno, JoshuaZ, Edwy, Chodorkovskiy, JorisvS, Mgiganteus1, Hernoor, IronGargoyle, SpyMagician, Jess Mars, Pogsquog, Ckatz, Riverkarl, The Man in Question, RandomCritic, ZincOrbie, Loadmaster, Slakr, Stwalkerster, Tac2z, Laogeodritt, Yvesnimmo, Suraj vas, Grandpafootsoldier, Samaster1991, KHAAAAAAAAAAN, Dicklyon, Funnybunny, Ryulong, Sijo Ripa, Gazjo, RichardF, Elb2000, Jose77, Michael Dinolfo, NuncAutNunquam, Kvng, Akademy, Politepunk, Tawkerbot, DabMachine, Webb.phillips, ILovePlankton, Iridescent, K, JMK, Jake1293, Michaelbusch, Shakedust, Dekaels, Polymerbringer, Paul venter, Lakers, Ktan, Joseph Solis in Australia, Scooter20, Halfblue, Newone, J Di, Dave420, Andrew Hampe, Diz syd 63, Hipporoo, Galaad2, CapitalR, Esurnir, Stereorock, Marysunshine, Civil Engineer III, Courcelles, Nkayesmith, Sxicrisis, Eluchil404, Tawkerbot2, Aldo12xu, Serb4c, Alegoo92, Dlohcierekim, Broberds, Daniel5127, Chetvorno, Poolkris, Altonbr, Firstmagnitude, Orangutan, Mr Woman, Fvasconcellos, Rondack, JForget, GeneralIroh, Taskmaster99, Mapsax, Vaughan Pratt, InvisibleK, WCar1930, Zooman555, Tanthalas39, Ale jrb, Wafulz, Tuvas, Crescentnebula, Aherunar, Woudloper, Kris Schnee, Drinibot, Ruslik0, GHe, N2e, Chmee2, WeggeBot, Moreschi, Itportal, Decadence- cavy, Phædrus, Ispy1981, Trunks6, Zaraahmed100, Ufviper, TJDay, Lightblade, Danrok, Nbound, ChristTrekker, Reywas92, Chilambu, Steel, PorciusXX, DrunkenSmurf, Gogo Dodo, Travelbird, Llort, M£, Torvik, Daniel J. Leivick, B, Tawkerbot4, Gvil, Chrislk02, Invader- Zod, Optimist on the run, Salulljoica, Bungle, ErrantX, Omicronpersei8, Nicoisgreat111, Daniel Olsen, PsychoSmith, Tejas.B, Richhoncho, -Casliber, Eubulide, Thijs!bot, Epbr123, Dbarnes99, Joshuagay, Coelacan, NeutralPoint, ChunkySoup, King Bee, Sal ,הסרפד ,Kirk Hilliard 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 119

adguy, LeeG, Ultimus, Nowimnthing, KimDabelsteinPetersen, Dasani, Aster2, Ezkerraldean, RolfSander, Illexsquid, Keraunos, Hexgirls, Alexvickers, Headbomb, Oubiwann, Dtgriscom, Jcarle, Tapir Terrific, Bad Astronomer, A3RO, Electron9, TheTruthiness, Gonzalolu- engo, Aaaa123, Wildthing61476, Ligguma, Pegstarr, Aquilosion, GregMinton, Hcobb, Srose, Ericmachmer, Angie023, Dawnseeker2000, AlefZet, Northumbrian, Escarbot, Sbandrews, Porqin, KrakatoaKatie, Sidasta, Hires an editor, AntiVandalBot, Yupik, Majorly, Yonatan, Luna Santin, Targetter, Mukake, Snicket101, Opelio, Czj, Gnixon, RDT2, Caggy, David136a, 17Drew, Waerloeg, Jj137, RogueNinja, Ereiyo, Spangs, MDB913, Dr. Submillimeter, Modernist, SkoreKeep, Kerdek, Qwerty Binary, Fearless Son, Wl219, Myanw, Willthepwn, Uchohan, Kaini, LordKael, PresN, Canadian-Bacon, Towelie55, HolyT, Ioeth, JAnDbot, Milonica, Deflective, Husond, Fidelfair, MER-C, CosineKitty, BlindEagle, Something14, TV4Fun, FrankStratford, Instinct, QuantumG, Fetchcomms, IanOsgood, Foodlover3935, Fac- toidCow, Hamsterlopithecus, MLetterle, Andonic, Dcooper, Cjkporter, Aubadaurada, Rentaferret, MakeDamnSure, Christopher , Hardee67, Rothorpe, Jespley, Suduser85, Matiasmoreno, Steveprutz, .anacondabot, Geniac, Yahel Guhan, Dpshuler, Meeples, WolfmanSF, Schmackity, Eisenmond, Pedro, Murgh, Bongwarrior, VoABot II, Monowiki, Hasek is the best, JamesBWatson, Tomhannen, Eltener, Gar- rett123, AMK1211, Rivertorch, Davart, Jespinos, SHA0001, Steven Walling, WODUP, RoseAstronomer06, Recurring dreams, Martin Ginty, Jack Schmidling, Bullzeye101, Catgut, Ludes, Indon, Panser Born, Superworms, Animum, Cyktsui, Mpanos2003, Scottcabal, Bat- teryIncluded, Bloodredrover, ArthurWeasley, RahadyanS, BeaverWithChainsaw, BilCat, Allstarecho, Japo, Dck7777, Spellmaster, Dock- worker, Just James, DerHexer, JaGa, Megalodon99, Torontobwoi, Patstuart, Info D, AOEU, Dudeguyryan, Eschnett, Wikianon, Kheider, Erpbridge, NatureA16, Marcairhart, Xagyg, Pauly04, Hdt83, MartinBot, Schmloof, 12345tyuio, DonnyKerabatsos, Ariel., Arjun01, ARC Gritt, Motley Crue Rocks, LordPhobos, Ben MacDui, Ambi Valent, Mschel, R'n'B, Flo422, CommonsDelinker, AlexiusHoratius, Nono64, Leyo, PrestonH, Lilac Soul, Darth Logan, AlphaEta, Watch37264, J.delanoy, Tinwelint, Abecedare, Veritas Blue, DrKiernan, CFCF, Trusilver, Carre, Svetovid, Rgoodermote, Dangoo, Tom Paine, UBeR, DomBot, Hans Dunkelberg, Lonjers, Agordhandas12788, Yeti Hunter, Kudpung, Music4ever1, Ljones0920, Nothingofwater, ABTU, Acalamari, Rc3784, Downhometown, JAW92, WikiBone, Dis- penser, Bot-Schafter, Ohfosho, Roger3245, Gman124, Phayne, Andy Johnston, Krako, Trumpet marietta 45750, Ljv05, OAC, Trvsdrlng, Gurchzilla, Leefatting, Chriswiki, Tpheiska, HiLo48, Wmfife, DDR-Physiker, Infinityfsho, NewEnglandYankee, Cadwaladr, Fountains of Bryn Mawr, Ohms law, SJP, Mvincec, SkogsRickard, Ljgua124, Prilla, Charlesblack, Haljackey, Cometstyles, Apexfreak, WJBscribe, Action Jackson IV, Drazyr, Supergeo, Sarregouset, DMCer, Natl1, Cs302b, CardinalDan, Idioma-bot, BradDeharder, Spellcast, Idarin, Jrt224, Uncfan3200, Makewater, Cactus Guru, Lights, Goalie1998, Caribbean H.Q., Vexxl, Cpollak, HamatoKameko, Roaring phoenix, Deor, Jturner773, Spaceman13, VolkovBot, Preston47, Thedjatclubrock, Johan1298, Meaningful Username, Ericdn, Leebo, Maile66, Rutherfordjigsaw, Bovineboy2008, Zoharby, Katydidit, Fences and windows, TheOtherJesse, CalviNet, Sdsds, Mattfox22, Philip True- man, Drunkenmonkey, Chiros Sunrider, TXiKiBoT, Spellcaster12, Tinsue, Dojarca, Renthead97, Eberk456, Malljaja, Mario0318, Mi- randa, Rei-bot, Playerfreakbass, FrstFrs, Anonymous Dissident, NVO, Ironman1503, Yunaresuka, Cosmium, Terence7, Eeron80, Master- Sci, Demanufacture, JhsBot, Leafyplant, Slysplace, The dyer man, Fbs. 13, LeaveSleaves, HuskyHuskie, Amog, Seb az86556, Pleroma, Onore Baka Sama, Nintendo121, Fartstank1996, Maxexcloo, Maxim, Bryan.dollery, ShapedNoise, Mr.Kennedy1, Pious7, Hellcat fighter, Tcmstr134, Norty512, Synthebot, Enviroboy, 11warnjames, Calypsos, Phantomdj, FKmailliW, Julian Herzog, WatermelonPotion, Insanity Incarnate, Kid45laundry, Jobberone, Wiggstar69, TheN0ble2, Smerlinare, AlleborgoBot, Bob the Rabbid, FreyasCrystalizedAngels, Luigi- Maniac, Jim Furtado, Vsst, EmxBot, Tedstryk, Oniwanbashuu, D. Recorder, Wraithdart, Mandynoty, Redandproud1, Viggio, Mediumemu, Justyb, Akira112, Lksadfajsl, Elisa Woods, SieBot, Ersatzaxiom, Dusti, I OWN I OWN I OWN, Jim77742, Tehtorptsol, PlanetStar, Non- Chalance, YonaBot, Spartan, Luboogers25, Oldag07, OlliffeObscurity, Legend, Buddyonline7, Parhamr, Caltas, Xymmax, Triwbe, Cara- par999, Vanished User 8a9b4725f8376, Stewartmacarth, Til Eulenspiegel, Wiljaneni, Jerryobject, Purbo T, Keilana, Chuckchuckerson, Maddiekate, Streetfoo212, Android Mouse, Aillema, RadicalOne, Radon210, Cbsteffen, Azzjiggla, Mirkoruckels, Drorion, Themulemonk, Derajenator, Wikipedophilia, Happyfeet999, John dildo, Wikipedosucklol, JustAnotherGuy01, RedandProud2, Lookypoojky, Helloasd, Djuice8, I need a stupid username, Sibalsagi, WikiUser55, Belar, That paddy child kid, Crip22, Jknhkjdfhhhhhhh5454, Merik777, Tim- myrprp, Andrew the coolest, Not Andrew, Mimihitam, Jacob beechler, Tezp, Oxymoron83, Antonio Lopez, Imdagirlonwiki, StivCa, Lightmouse, Tombomp, AMCKen, Radzewicz, Murlough23, Schnahoo, T42at102, Alex.muller, Triberocker, BenoniBot, OKBot, Ben- nish, Svick, Maelgwnbot, LonelyMarble, Hiei-Touya-icedemon, AghastAmok, JohnnyMrNinja, Oldey, AWESOME-Odude, Jacob.jose, Sean.hoyland, Randomblue, Hamiltondaniel, Konomono33, Killerman1, Choptube, Ascidian, Statue2, Nash London, Florentino floro, Je- sus the savior, Marsterritory, Pinkadelica, Gregs gunners, Supraboy001, Schuylar247, Escape Orbit, AndySmith84, C0nanPayne, Ayleuss, Wjmummert, Starcluster, Lol0075, Glades2, Athenean, SallyForth123, MenoBot, Martarius, Marzziano, Friend mole, ClueBot, Avenged Eightfold, PipepBot, Foxj, The Thing That Should Not Be, Sammmttt, Revan13, John.D.Ward, Rjd0060, Bobith2, Skater1345, Trav- isjoake22130, Taliska, Blaablaa, Ezzex, Harmony5, JTBX, Gamehero, Gigarice, Niceguyedc, Nanobear, VgerNeedsTheInfo, Rotational, Filip.vidinovski, Suniti karunatillake, Neverquick, Lampofdoom, Phenylalanine, House13, Jlarvae, Gthy1, B2012ball21, FrancescoA, Ex- cirial, Jonapello22, Jusdafax, Hargitai, Nerguy, PixelBot, Sun Creator, BaconBoy914, Fukiyow, NuclearWarfare, Sepeople, SO-intO- yOuxX, Cenarium, Jotterbot, Jo Weber, Dustymars, Scog, Razorflame, SockPuppetForTomruen, Redthoreau, BOTarate, Stepheng3, John Paul Parks, Thingg, Bagunceiro, ApostleJoe, Goat217, BetoCG, GrahamDo, Kubek15, Helzart, Claytopia3, TheLasso, Sethrasmussen121, DumZiBoT, Thetreesonmars, Showbread89, Aaronbwsm, UltraCaution, Spotturtle, Bluhbluhbluh94, Sk8rbabii202, DrOxacropheles, Belekvor, Rror, Aldude14, Astrofreak92, Avoided, Stephen27, Mitch Ames, Blast Ulna, Noctibus, WikiDao, Anixea, Mikewilson614, Dahn10, Airplaneman, SugarPlumLove, Homrsmpsnrulz, Headasploder, Xerbox, Kbdankbot, Olyus, Notmage2, Maldek, Kasey12297, Roentgenium111, Chihuahua22, Lagus970, DOI bot, Jojhutton, HannahCRichards, Wonkinson, EjsBot, SigmaTap, Ronhjones, Kbc- fan, PC-Cat, Delfinis, CanadianLinuxUser, Leszek Jańczuk, Wælgæst wæfre, Dyadron, NjardarBot, Skyezx, Koolgirl560, LaaknorBot, CarsracBot, RebaFan1996, Glass Sword, Debresser, Favonian, LinkFA-Bot, West.andrew.g, Ks 7508, Peti610botH, Renatokeshet, Fresh- groundcoffee, 84user, Sanawon, Numbo3-bot, Ace45954, The mars 789, Tide rolls, Sumguynamedj, Gail, SexualFinger, Wikichanger- man, DrKeirnan, Hugsnkisses1996, Nubar24, Margin1522, Luckas-bot, Yobot, Randomguy1234567890, Beerdola, LightingRod, Nin- jalemming, II MusLiM HyBRiD II, KamikazeBot, Dmarquard, AnomieBOT, KingofGnG, Archon 2488, SwiftlyTilt, 1exec1, Dwayne, JackieBot, Lwangaman, Brutchersp, Ivan2007, Materialscientist, Redranger141, RadioBroadcast, Citation bot, JohnFromPinckney, Lil- Helpa, Lqstuart, Obersachsebot, Xqbot, Link dude177, TinucherianBot II, Timir2, Intelati, Clydecoast, Drilnoth, Smk65536, Gilo1969, Boltz6100, Oncedarkness, Toa Nidhiki05, Tyrol5, Mlpearc, Arsia Mons, Jimwilcox79, GrouchoBot, Maria Sieglinda von Nudeldorf, Zefr, RibotBOT, Enceladusgeysers, Charvest, GhalyBot, Silbad, Samwb123, Fotaun, Zytroft, Diamondhead123, Celuici, DasallmächtigeJ, Green Cardamom, Dave3457, Depictionimage, Lukepolick, FrescoBot, Surv1v4l1st, Originalwana, Kuliwil, Tobby72, Io Herodotus, Lookang, KokkaShinto, Majopius, 培养皿, Kwiki, TheLou75, Citation bot 1, Pinethicket, Metricmike, Tardblog, HRoestBot, Abductive, Princes- sofLlyr, 10metreh, Rameshngbot, Tom.Reding, Supreme Deliciousness, Lithium cyanide, RedBot, Brian Everlasting, Gingermint, Mohe- hab, Σ, Amitrc7th, Forward Unto Dawn, Mikebarryrocks!, Ras67, Fartherred, Skounave, IVAN3MAN, Tim1357, Crosscountry511, Kgrad, FoxBot, Double sharp, TobeBot, Trappist the monk, Ksanexx, DixonDBot, Train2104, Arivu jevi, Tony24644, Vrenator, Begoon, Pi- lot850, Diannaa, Jhenderson777, Earthandmoon, Patsfanwow, Tbhotch, Рулин, Deanmullen09, Hornlitz, Sideways713, Shanefb, DARTH SIDIOUS 2, Purz12, RjwilmsiBot, TjBot, Benyoch, Ripchip Bot, NerdyScienceDude, Burmiester, Wintonian, Slon02, DASHBot, Emaus- Bot, John of Reading, WikitanvirBot, Oodgoo, Gfoley4, Inconsistentlysane, Ajraddatz, Pluszero, Giornorosso, GoingBatty, Heljqfy, Mar- 120 CHAPTER 7. VENUS

tinThoma, Gwillhickers, Wham Rock II, Jmencisom, Challisrussia, K6ka, Japol1, Lamb99, AvicBot, ZéroBot, Stoner4life, Josve05a, A2soup, Cosmoskramer, Emily Jensen, Nkwatra3, Noelwww, Jdixo17, Stickychew97, AvicAWB, Hevron1998, Aeonx, H3llBot, Enia- grom, NoOneAsked, Fabian Hassler, Ocaasi, Wabbott9, Samibrown98, Jman291, L1A1 FAL, 3sdanog, Boomchakalaka2, Brandmeister, Alvez3, L Kensington, Dante51763, JeanPiaget, Surajt88, R1r1f2, Epicstonemason, Sailsbystars, Fanyavizuri, Kaijen176, Spongebob210, Scoliosis, Johnny893, -xwingsx-, ChuispastonBot, Tehrandomguy101, Lee60480, Kkkylek, Planet photometry, Llightex, DASHBotAV, Aussie895, Layneah, Whoop whoop pull up, Mssipress, Jonininini, ClueBot NG, Xession, Movses-bot, Jboratko, Frietjes, Dingowasher, Habil zare, Kasirbot, Alexrybak, Helpful Pixie Bot, Vortex320, Bibcode Bot, BG19bot, MKar, Guy vandegrift, Hz.tiang, Qwerty1219, Frze, AvocatoBot, Dodshe, Chris the Paleontologist, Cadiomals, Piisawesome, Jnanaranjan sahu, Cryptiddude, Sacchipersempr, Tratchy, Tycho Magnetic Anomaly-1, Colinmartin74, Zedshort, Silvio1973, Ubiquinoid, Holyjoe722, BattyBot, Tonyhayes, Hansen Sebastian, Nick.mon, Renilweb, EagerToddler39, Dexbot, Rezonansowy, Naapple, LightandDark2000, Mogism, Clockery, Siberian Patriot, Havebased123, 3er40, Typesometext, 134340Goat, JustAMuggle, Reatlas, Joeinwiki, Xwoodsterchinx, MinecraftFan2012, PC-XT, F6Zman, Jcpag2012, SaturatedFats, Dustin V. S., Lindenhurst Liberty, Tony johnsong, CensoredScribe, Carbon6, JeanLucMargot, Exoplanetaryscience, Cptm- rmcmillan, Anrnusna, Jamie.Taylor92, PlayStation 14, Monkbot, Allytoon, Filedelinkerbot, Scarlettail, Spideratseds, Tetra quark, Isambard Kingdom, TheWhistleGag, Supdiop and Anonymous: 1408 • Mercury Source: http://en.wikipedia.org/wiki/Mercury?oldid=655885043 Contributors: RjLesch, The Cunctator, Lee Daniel Crocker, Bryan Derksen, Zundark, Stephen Gilbert, -- April, Andre Engels, XJaM, Enchanter, Hephaestos, Olivier, Chuq, RTC, Eric119, Minesweeper, Egil, KAMiKAZOW, TUF-KAT, Angela, Evercat, GCarty, Smack, Conti, Timwi, Dcoetzee, Ike9898, Doradus, DJ - worth, Morven, Joseaperez, Renato Caniatti, Jusjih, Flockmeal, Francs2000, Denelson83, Branddobbe, Rossnixon, Paul Klenk, Kristof vt, Romanm, Academic Challenger, Steeev, Meelar, Hadal, Tobias Bergemann, Filemon, David Gerard, Thv, Marnanel, Monedula, Bkon- rad, Curps, Bensaccount, Beardo, Matt Crypto, Joseph Dwayne, ChicXulub, Antandrus, The Singing Badger, Mzajac, A. J. A. DeWitt, Nzseries1, Meweight, Icairns, Urhixidur, Ukexpat, JavaTenor, Andylkl, Freakofnurture, N328KF, Discospinster, Silence, Xezbeth, Alis- tair1978, Brian0918, CanisRufus, QuartierLatin1968, Deanos, T-bomb, Femto, Bobo192, Acntx, Kjkolb, A2Kafir, Linuxlad, Jumbuck, Alansohn, QVanillaQ, Mo0, Velella, ReyBrujo, Yuckfoo, Suruena, Evil Monkey, De Guerre, TheCoffee, Eddie2, HenryLi, Kitch, Stephen, Thryduulf, Pekinensis, Georgia guy, Barrylb, Julo, El Suizo, Shikai shaw, SeventyThree, Dovid, Palica, Dysepsion, Graham87, Marcg106, Yuriybrisk, BD2412, Josh Parris, Canderson7, Twrist, Quiddity, Stardust8212, Feydey, Lordkinbote, Nightfreak, MooseBlaster, McPhail, Demnevanni, RexNL, Gurch, Karrmann, King of Hearts, Chobot, EvilZak, Gwernol, YurikBot, Retodon8, No Account, Red Slash, Me and, Qwertzy2, Hellbus, Havok, Kimchi.sg, Wimt, NawlinWiki, Rick lay95, Nick C, Zwobot, Wangi, Bota47, Hosterweis, Kal-El, Wknight94, Theda, Fang Aili, §, Petri Krohn, 2fort5r, Curpsbot-unicodify, Chaiken, Katieh5584, Paul Erik, Serendipodous, Nofxjunkee, F, Herostra- tus, Prodego, The Monster, Unyoyega, Y control, Jrockley, Canthusus, Edgar181, Alsandro, Yamaguchi 先生, Gilliam, Hraefen, Chris the speller, Agateller, MalafayaBot, Gareth, Bonni, Scwlong, MyNameIsVlad, Xyzzyplugh, Darwin's Bulldog, Addshore, Mipchunk, Nakon, NaySay, Ultraexactzz, Jonmmorgan, Checco, JanderVK, Korean alpha for knowledge, Shlomke, Ckatz, Tetrachloromethane, JHunterJ, SQGibbon, ShakingSpirit, BranStark, Clarityfiend, Epistemos, Trialsanderrors, Jontomkittredge, Markbassett, Tawkerbot2, MightyWar- rior, JForget, CmdrObot, Tanthalas39, Ale jrb, Earthlyreason, Dycedarg, Makeemlighter, ShelfSkewed, Shield1785, Vectro, Gogo Dodo, Anthonyhcole, Arrowned, Timmie.merc, Thijs!bot, Epbr123, Barticus88, Cain Mosni, John254, Kathovo, TXiKi, Wai Wai, Escarbot, Caleson, Dainis, Charles Brooking, AntiVandalBot, Prolog, Fayenatic london, LibLord, Dougher, Ioeth, JAnDbot, NapoliRoma, RR, LittleOldMe, Magioladitis, Gekedo, Bongwarrior, VoABot II, BrianMandell, AuburnPilot, Dulciana, Ohwell32, Enquire, Pax:Vobiscum, Skaritista, MartinBot, Nando.sm, ViperBlade, Huzzlet the bot, Watch37264, J.delanoy, Child of Albion, Love Krittaya, SU Linguist, Calvins48, Gzkn, Bigdumbdinosaur, Evil lemming, Jamesontai, WarFox, LordCo Centre, Cruftbane, Treisijs, Toll Booth Willie, James- ryanjcrjcr, Num1dgen, Martial75, Lights, Hellno2, VolkovBot, Claudia rocks, Jeff G., Lear's Fool, Classical geographer, QuackGuru, Philip Trueman, TXiKiBoT, Alan Rockefeller, Gerrish, Vanished user ikijeirw34iuaeolaseriffic, LeaveSleaves, UnitedStatesian, Kipicorn, Kimjim, Madhero88, Sitacuisses, Chocolatemilk91, Brian Huffman, Billinghurst, Andy Dingley, Synthebot, Enviroboy, I will take over wikipedia, Insanity Incarnate, Twooars, AlleborgoBot, PGWG, Milowent, Neparis, Vasili77, Udderguy, EJF, SieBot, TJRC, Tiddly Tom, Jauerback, Caltas, Sinsom, Dattebayo321, Keilana, Pengzell, Screwed13927, Oda Mari, Jjkr, StaticGull, Mtaylor848, ClueBot, Engelalber, Foxj, The Thing That Should Not Be, Drmies, CounterVandalismBot, SamuelTheGhost, Excirial, Mr.Z-man.sock, Quercus basaseachi- censis, Alexbot, CrazyChemGuy, Net Hacker, Corysn123, NiciVampireHeart, NuclearWarfare, Jotterbot, Dustpelt96, BOTarate, Thingg, Versus22, Miami33139, Budelberger, Skunkboy74, Wertuose, BodhisattvaBot, Rror, 13chaujf1, Netrat, On the other side, Addbot, Fyrael, AlexWangombe, Fieldday-sunday, Skyezx, Download, FiriBot, Tassedethe, Williamhortner, DubaiTerminator, Tide rolls, Mjquinn id, Zor- robot, Bobers123, Luckas-bot, Yobot, Cflm001, Darfellan, ByM4k5, AVB, Tempodivalse, AnomieBOT, Nording, JackieBot, Theseeker4, Materialscientist, Tinghokavin, Speculos, Parthian Scribe, MauritsBot, Xqbot, Berganus, Hys baby, Cureden, Capricorn42, Sup30, YBG, Bayleo, Inferno, Lord of Penguins, GrouchoBot, Jezhotwells, RibotBOT, Jordan413, Qwesdfq, Aaa41, Bigboy004, Natural Cut, Ninunav, A. di M., Emmyb11, SD5, Koobalocks, Saehrimnir, Lilnelly22, Pinethicket, Nickgonzalez, Achaemenes, RedBot, ContinueWithCau- tion, Shooting rox03, Cnwilliams, TobeBot, Ticklewickleukulele, Jburrows09, Qzm, Vrenator, Samsoup, JnRouvignac, Yellow Flash77, MegaSloth, Ripchip Bot, Skamecrazy123, EmausBot, Tommy2010, Sepguilherme, Josve05a, GrouseyGrouse, Wayne Slam, Rcsprinter123, DOwenWilliams, Ego White Tray, ChuispastonBot, DASHBotAV, Tvise1, ClueBot NG, Satellizer, Gaob, Rezabot, LOLSmileyMiley13, Danim, Anupmehra, Wbm1058, Pratyya Ghosh, Longfellow300, DOOman68, Lugia2453, Basedastronomy69, Metru2000, Eyesnore, Tentinator, Nickwilliams270203, Oliver hacker pro, TheEpTic, Phleg1, Riddleh, DarkxIllutionz, Dillyop, Bazinga.321 and Anonymous: 338 • Neptune Source: http://en.wikipedia.org/wiki/Neptune?oldid=654261627 Contributors: Paul Drye, Chuck Smith, Brion VIBBER, Mav, Bryan Derksen, The Anome, Stephen Gilbert, Jeronimo, -- April, Ed Poor, Amillar, Eob, Scipius, Youssefsan, XJaM, Rmhermen, Chris- tian List, Roadrunner, SimonP, B4hand, Montrealais, Chuq, Spiff, Frecklefoot, Michael Hardy, Oliver Pereira, Gdarin, Vera Cruz, Ixfd64, (, Iluvcapra, Minesweeper, Alfio, Kosebamse, Egil, Looxix, Ahoerstemeier, William M. Connolley, Snoyes, Mark Foskey, Setu, Glenn, Cyan, Poor Yorick, Evercat, Gh, Pizza Puzzle, Schneelocke, Hike395, Timwi, Denni, Colipon, Dandrake, Fuzheado, Doradus, Timc, DJ Clayworth, Haukurth, Tempshill, Ed g2s, Rnbc, Head, Traroth, Shizhao, Mignon, Bloodshedder, Northgrove, Twang, Donarreiskoffer, Branddobbe, Nufy8, Robbot, Naddy, Lowellian, Merovingian, Hadal, Wikibot, Dmn, Cutler, Dina, Alan Liefting, Ploum's, Dave6, Stir- ling Newberry, ShutterBugTrekker, Nephelin, Giftlite, JamesMLane, DocWatson42, Djinn112, Awolf002, Jyril, ShaunMacPherson, Harp, Wolfkeeper, Obli, Everyking, Curps, Michael Devore, Henry Flower, JamesHoadley, MingMecca, Zaphod Beeblebrox, BrendanRyan, Pne, AdamJacobMuller, Sesel, Wmahan, ChicXulub, SoWhy, Patteroast, Alexf, Semprini, Zeimusu, Junuxx, Vinay, Antandrus, The Singing Badger, HorsePunchKid, Beland, Eroica, JoJan, Vanished user 1234567890, PDH, Rdsmith4, Thincat, Borameer, Gscshoyru, Neutral- ity, Urhixidur, Edsanville, Ukexpat, Lacrimosus, Mike Rosoft, Ouro, Venu62, Monkeyman, DanielCD, JTN, Indosauros, Discospinster, Rich Farmbrough, Guanabot, Ponder, Arthur Holland, Mani1, MuDavid, Paul August, SpookyMulder, Kenb215, Bender235, Cyclopia, Brian0918, RJHall, Ylee, El C, DS1953, Lankiveil, Joanjoc, Kwamikagami, Worldtraveller, Shanes, Tom, Hairyshoe, Remember, Art LaPella, Femto, Iridia, Causa sui, Bobo192, Circeus, NetBot, BrokenSegue, Olve Utne, Elipongo, L33tminion, I9Q79oL78KiL0QTFHgyc, Jerryseinfeld, Irrawaddy, Jojit fb, TheProject, Cherlin, BillCook, Sam Korn, Pharos, Supersexyspacemonkey, Storm Rider, Danski14, Bob 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 121

rulz, Alansohn, QVanillaQ, Verdlanco, Derumi, Axl, RoySmith, Alex '05, Spangineer, Avenue, VladimirKorablin, Snowolf, Burwellian, Bucephalus, BaronLarf, SidP, Gdavidp, Almafeta, Suruena, Evil Monkey, Tony Sidaway, Jon Cates, RainbowOfLight, Inge-Lyubov, Gene Nygaard, Capecodeph, Tobyc75, HenryLi, Sturmde, Kitch, TShilo12, Siafu, WilliamKF, Sterio, Bacteria, OwenX, Woohookitty, BreathingMeat, JarlaxleArtemis, TigerShark, LOL, HisHighness420, BillC, Dayv, MONGO, Miss Madeline, Firien, Steinbach, Sengkang, GregorB, Wayward, Smartech, Dysepsion, Paxsimius, Regulus32, Graham87, Marskell, Chun-hian, MC MasterChef, FreplySpang, Nl- sanand, GrundyCamellia, Pentawing, Canderson7, Drbogdan, Rjwilmsi, Angusmclellan, Koavf, Virtualphtn, NatusRoma, Jake Warten- berg, Wikibofh, BlueMoonlet, Seraphimblade, Soakologist, Mike s, Mike Peel, XLerate, Kazrak, SeanMack, Brighterorange, Bhadani, Dar-Ape, Sango123, Dea123, Yamamoto Ichiro, Algebra, FayssalF, FlaBot, Splarka, Ian Pitchford, RobertG, Nihiltres, RexNL, Chong- Dae, Arctic.gnome, Str1977, TeaDrinker, Alphachimp, Srleffler, Ahwaz, Russavia, Aasmith, King of Hearts, Chobot, Visor, Sharkface217, Jared Preston, Antiuser, Digitalme, Tone, Hrwiki, Bperry7, Wavelength, TexasAndroid, Sceptre, Hairy Dude, Prometheus235, Vlad4599, Pleonic, Killervogel5, Jumbo Snails, Notyourbroom, SnoopY, SpuriousQ, Wikispork, Chaser, Hellbus, Shawn81, Rodasmith, Kerowren, Hydrargyrum, Dotancohen, Stephenb, Zhatt, CambridgeBayWeather, Pseudomonas, Wimt, Burek, NawlinWiki, Wiki alf, BGManofID, Johann Wolfgang, SomeYoungGuy, Mmccalpin, Toucan6, R'son-W, Dureo, Irishguy, Ravedave, Iggi.au, Chal7ds, Raven4x4x, Killdevil, Zwobot, Ospalh, Nate1481, Rdl381, BOT-Superzerocool, PrimeCupEevee, DeadEyeArrow, Psy guy, T-, Dna-webmaster, Wknight94, Gunis del, 21655, Zzuuzz, Kandrey89, Chaos syndrome, Theda, Closedmouth, Reyk, Modify, JoanneB, CWenger, Nae'blis, Kier07, Hurri- cane Devon, Tarquin Binary, Junglecat, KNHaw, Iago Dali, Serendipodous, DVD R W, That Guy, From That Show!, Dragon of the Pants, Caponer, Deuar, Sardanaphalus, Anton n, Sintonak.X, RupertMillard, SmackBot, Battle Ape, Saravask, Bobet, Prodego, KnowledgeOfSelf, Hydrogen Iodide, Cavenba, Rayward, WilyD, Neptunius, Mscuthbert, EncycloPetey, Delldot, Alsandro, Gaff, Pinpoint23, Nabs, Skizzik, Andy M. Wang, Teleros, Saros136, Bluebot, Kurykh, Keegan, Persian Poet Gal, Rick7425, Northern, Hibernian, The Rogue Penguin, Kaid100, Oni Ookami Alfador, Ctbolt, Baa, DHN-bot, Sbharris, Chr.K., Bil1, AKMask, Gracenotes, Gyrobo, Lewis007, Scwlong, King of the Dancehall, Can't sleep, clown will eat me, Shalom Yechiel, Fairychild, Mourn, Mrwuggs, Typofixer76, Astrobhadauria, Rrburke, Mhym, Celarnor, AgentFade2Black, Fuhghettaboutit, Khukri, Nakon, Caniago, T-borg, Jennifer T, Metebelis, Kneale, Mini-Geek, Sbluen, Wiz- ardman, Zonk43, Kendrick7, ALK, Er Komandante, Risker, Samuel Sol, Thebends, Ohconfucius, SashatoBot, Lambiam, Esrever, Xyad, Harryboyles, Rklawton, John, Cwilli201, Moleskin, Korean alpha for knowledge, Khono, VirtualDave, Shlomke, JoshuaZ, Edwy, JorisvS, Temple, JayMan, Youngcc7, Goodnightmush, Diverman, Hernoor, Bilby, Jess Mars, PseudoSudo, Ckatz, RandomCritic, Eivind F Øyan- gen, JHunterJ, MarkSutton, Serpentinite, Kyphe, Special-T, Werdan7, 81120906713, Muadd, Luokehao, Eurocommuter, InedibleHulk, Waggers, SandyGeorgia, Ryulong, A Clown in the Dark, RichardF, Elb2000, Jose77, Peyre, Caiaffa, Politepunk, Norm mit, BranStark, Iridescent, Michaelbusch, Dekaels, Joseph Solis in Australia, Michael Shade, McJeff, Shoeofdeath, Hipporoo, Igoldste, Ouzo, Tony Fox, CapitalR, Az1568, Courcelles, Danielg001, Tawkerbot2, Acom, Filelakeshoe, Poolkris, Chris55, Xcentaur, JForget, SpaceHouse, Adam Keller, CmdrObot, Ale jrb, Mattbr, Wafulz, Dycedarg, Ric36, Myrrhlin, Bumcheekcity, Vyznev Xnebara, Drinibot, CWY2190, Rus- lik0, Benwildeboer, Dgw, WeggeBot, Logical2u, SelfStudyBuddy, Moreschi, Karenjc, RobertLovesPi, MrFish, Ufviper, Sopoforic, Cy- debot, Natasha2006, Nbound, Abeg92, ChristTrekker, Treybien, Gogo Dodo, Ericfassbender, JFreeman, Corpx, Gv365, Q43, StaticElec- tric, Jc42, Kozuch, Lewisskinner, Omicronpersei8, Jeremy77q, TAIWAN, Rocket000, LukeS, Casliber, FrancoGG, Thijs!bot, JAF1970, Epbr123, Wikid77, Jaxsonjo, Faigl.ladislav, Martin Hogbin, Illexsquid, Keraunos, Colosimo, Headbomb, Paper Clip Clock, Möchtegern, John254, Bad Astronomer, Electron9, Ufwuct, Donnap1957, Wildthing61476, Davidhorman, Dfrg.msc, Pcbene, CharlotteWebb, The Hybrid, Dawnseeker2000, Natalie Erin, RoboServien, SomeHuman, Escarbot, AntiVandalBot, Jeames, Jimspon7, Luna Santin, Opelio, Erwin85Bot, Paste, BigThunderMtn, Dr. Submillimeter, Gdo01, Once in a Blue Moon, SkoreKeep, PresN, Raukodacil, JAnDbot, De- flective, Husond, MER-C, BlindEagle, James919, Instinct, Kaabi, Db099221, Andonic, Hut 8.5, Rentaferret, PhilKnight, Rothorpe, Acro- terion, SteveSims, Bencherlite, ArthurianLegend, WolfmanSF, BMW Z3, Freedomlinux, Pedro, Murgh, VoABot II, Mileage, Tomhan- nen, Think outside the box, Rivertorch, Bigdan201, Midgrid, Gr1st, Bubba hotep, BrianGV, Catgut, Animum, Pausch, Cyktsui, Arthur- Weasley, Randoman412, 28421u2232nfenfcenc, BilCat, Benny d, Chivista, Romancer, Glen, Chris G, DerHexer, JaGa, Megalodon99, Lenticel, WLU, TheRanger, The Sanctuary Sparrow, Kheider, Gwern, Mithras6, Jasonater, MartinBot, FlieGerFaUstMe262, Kingw0ng, Nohsvideoguy, Arjun01, Sunbursts, Dufort, Rettetast, Roastytoast, Juansidious, Cosumel, Keith D, Ambi Valent, Mschel, Com- monsDelinker, AlexiusHoratius, Hengist100, CASfan, Pbroks13, Dorieo21, Arpierson, Smokizzy, Ducksauce101, Artaxiad, Sedated- Godzilla, Beehive101, Paranomia, Watch37264, J.delanoy, Captain panda, DrKiernan, Trusilver, Planemo, AstroHurricane001, Ali, Bo- gey97, Lizrael, Mnshacodi, BillWSmithJr, Nigholith, GuitarFreak, WarthogDemon, E. Schenk, Acalamari, Stompin' Tom, Bot-Schafter, Katalaveno, Mr Rookles, Superiorrob, Gman124, Jeepday, Skier Dude, AntiSpamBot, Richard D. LeCour, NewEnglandYankee, Srp- nor, Theawsomelife, Rominandreu, Fountains of Bryn Mawr, SmilesALot, Ohms law, SJP, Toon05, Mufka, Shoessss, Thundergoalie73, MetsFan76, Renvarian, Cmichael, Atropos235, Evb-wiki, RB972, Seventypercent, Spiral Wave, U.S.A.U.S.A.U.S.A., Syu9019, Mjzwick, Arvind Vyas, Doctoroxenbriery, Jarry1250, Useight, Abasher, Planetwaves, DeadHd1995, GrahamHardy, CardinalDan, Idioma-bot, Ka- zooieman, Isayyum, Fainites, Stewader, Flatline121313413, PeaceNT, Chinneeb, Georgetherock, Deor, King Lopez, ThrustVectoring, VolkovBot, Thedjatclubrock, Johan1298, Choft, Leebo, Nburden, Mike=200006, Alexandria, AlnoktaBOT, Toddles29, Rutherfordjigsaw, Katydidit, Boaex, Alexkorn, Station1, Philip Trueman, Amos Han, TXiKiBoT, GimmeBot, SwiftAce, Maximillion , Hqb, Qaletaqa, TheresJamInTheHills, Rei-bot, Ann Stouter, Z.E.R.O., Google92, Yovinedelcielo, Qxz, Retiono Virginian, Lradrama, Seraphim, Melsaran, MasterSci, Leafyplant, Broadbot, Raymondwinn, Seb az86556, Pleroma, UnitedStatesian, Picturef1, Emilyxo1017, Imagecrafting, Am- stoakes, Kipicorn, Maxexcloo, Hello556, Orange-kun, Soccergirl9867, BigDunc, Roland Kaufmann, Pious7, Milkbreath, Sarc37, Go-in, Enviroboy, Imsamuel6, Brandonvas, Sylent, Insanity Incarnate, Ceranthor, AlleborgoBot, Suresh Nat, Funeral, King food, Tvinh, Ok- labama, Moofman22, Jeodo, School134524, Bensational, Steven Weston, Oceanball, EJF, SieBot, Dudeofdude2123, Kfc1864, Jim77742, Tresiden, Akliman, PlanetStar, Tiddly Tom, Work permit, Scarian, Euryalus, ToePeu.bot, Oldag07, Spacedrive, KGyST, Jsc83, Caltas, Universe=atom, Latin pimp, Nickyddogg, Yintan, Keilana, Iames, RadicalOne, Exert, Comkidwizzer3, Ooodrey19, Oda Mari, Arbor to SJ, Sohelpme, Pigger500, EastCoastPwnerz, Bram358, Hahaha34, Ayudante, 712yo, Oxymoron83, Aminghane, Faradayplank, AngelOfSad- ness, Lightmouse, Poindexter Propellerhead, Zacplaysgames, Murlough23, Mollykate8, Torchii, BenoniBot, Halcionne, Macy, Diego Grez, Dannyfat, Spliffmon, Maelgwnbot, LonelyMarble, Alatari, Jacob.jose, Randomblue, Hamiltondaniel, Venom124, Dust Filter, Nergaal, Efe, Spirit13, Jons63, Escape Orbit, AndySmith84, C0nanPayne, Starcluster, Shrewpelt, Kanonkas, Freewayguy, 07, BHenry1969, ClueBot, LAX, Artichoker, PipepBot, Bobathon71, Rjd0060, Lawrence Cohen, Bobisbob, Shinpah1, Jimfandango, Jdford10, Jed Bartlet, CounterVandalismBot, Hhhhhsfvg, Blanchardb, Neverquick, ChandlerMapBot, Klm815, DragonBot, Stepshep, SapientiaSativa, Robert Skyhawk, Excirial, AssegaiAli, Loph10, Alexbot, CrazyChemGuy, Gtstricky, Leonard^Bloom, Vivio Testarossa, Rhatsa26X, Sun Creator, NuclearWarfare, Arjayay, Jotterbot, PhySusie, Ember of Light, CowboySpartan, Razorflame, Radtek67, TOSYuan3195, BOTarate, Star- blazer123, Thingg, Ababababababab, Aitias, Wcp07, ClanCC, Anubad95, Neuralwarp, Cgallstar27, Swift as an Eagle, Dtpeck, Mattrave, Dora-bobba, 68Kustom, Coopman86, Badgernet, WikiDao, JinJian, 0pulse, MystBot, Mvgirl13, NFRANGA, Hunter Kahn, Kbdankbot, Jtknowles, Eello555, Sunsetsunrise, RX8Chic, Roentgenium111, AVand, Some jerk on the Internet, Rini genes, I eat gym socks, DOI bot, Element16, TutterMouse, CanadianLinuxUser, Ronkonkaman, Heremod, LaaknorBot, Delaszk, Stevethepirate1001, Rickybobby1001, Shortkicks4, Ghsfan13, LinkFA-Bot, Vivelafranceduex, EvelynFl, Flanagan33, Chicken likin, Numbo3-bot, Sc8erboi42, Ehrenkater, Tide 122 CHAPTER 7. VENUS

rolls, Lightbot, OlEnglish, Gail, Azdel, Cote d'Azur, Luckas-bot, Yobot, Ptbotgourou, II MusLiM HyBRiD II, Aldebaran66, Monkey- doo412, YngNorman, Dickdock, DanTheMan702, Hybridcar1, AnomieBOT, Archon 2488, Galoubet, Materialscientist, Frankietang, Citation bot, ArthurBot, Dspetc, Jlg4104, MauritsBot, Xqbot, Timir2, Smk65536, Amore Mio, Jmundo, Srich32977, Almabot, Grou- choBot, Ataleh, SassoBot, Jalapenos do exist, The Wiki ghost, Doulos Christos, Modestas rukky, Dnywlsh, Pikaman, Bff98765, GNRY09, Conrad, 16 year old girl, Doowop13579, Sk8erdude22, Tyroni96, Qwerty on Willy, Mommy87675, 911alloveragain911, Bryschneider, Coolestmidget13, Taravellacane, Silbad, Cookay569, Jorgie1, Fotaun, FrescoBot, LucienBOT, Lookang, Dalyup!, Bill the Cat 7, Armigo, Kobrabones, HRoestBot, Jonesey95, Tom.Reding, RedBot, Lars Washington, MastiBot, Googlemeister, Fartherred, IVAN3MAN, Light- lowemon, FoxBot, Double sharp, Trappist the monk, PS3ninja, Stephen MUFC, Gondor2222, Tbhotch, Shanefb, RjwilmsiBot, TjBot, Alph Bot, Burmiester, Kiko4564, DASHBot, EmausBot, Hoosier1989, WikitanvirBot, Qurq, Gored82, Jmencisom, P. S. F. Freitas, Noth- ing149, ZéroBot, CanonLawJunkie, Josve05a, A2soup, Nicolas Eynaud, AvicAWB, Hevron1998, H3llBot, Mlpearc Public, Мл.научный сотрудник, L Kensington, Richard Tuckwell, Silliking, Sailsbystars, MarkHurn, Adelson Velsky Landis, Honesty First, ChuispastonBot, Fjörgynn, ClueBot NG, Inoyu49, Faber01, Yanclae, Lanthanum-138, Delusion23, Castncoot, Diyar se, Helpful Pixie Bot, Newyork1501, Gob Lofa, Bibcode Bot, Dalit Llama, MKar, Lo Ximiendo, Hz.tiang, Leonxlin, AvocatoBot, Dodshe, Gallina3795, AstroRobster, Ca- diomals, Rgbc2000, Tycho Magnetic Anomaly-1, Ubiquinoid, Et Cum Spiritu Tuo, SoylentPurple, DarafshBot, W.D., Kelvinsong, Asis- man, Dexbot, AaronMP84, JustAMuggle, Reatlas, Redd Foxx 1991, Jcpag2012, JPaestpreornJeolhlna, Dustin V. S., Lindenhurst Liberty, SeventeenTurtle, YoungDrac, UltraMario64, Exoplanetaryscience, Stamptrader, Cancina5645, PlayStation 14, Monkbot, Trackteur, Spi- derjerky, Tetra quark, Isambard Kingdom and Anonymous: 1328

• Saturn Source: http://en.wikipedia.org/wiki/Saturn?oldid=655790788 Contributors: Magnus Manske, Derek Ross, Brion VIBBER, Mav, Bryan Derksen, Malcolm Farmer, -- April, Mark, Ed Poor, Andre Engels, Eob, Scipius, XJaM, JeLuF, Rmhermen, Christian List, SimonP, Camembert, Fonzy, Spiff, D, JohnOwens, Michael Hardy, Tim Starling, Lexor, MartinHarper, Gabbe, Ixfd64, Frank Shearar, Delirium, (, Iluvcapra, Minesweeper, Alfio, Tregoweth, Egil, Looxix, Ihcoyc, Ahoerstemeier, Caid Raspa, Rlandmann, Setu, Julesd, Glenn, Poor Yorick, Nikai, Andres, Kaihsu, Evercat, Mxn, Schneelocke, Mechanolatry, Hike395, Hashar, The Tom, Timwi, David Newton, Fuzheado, Doradus, Haukurth, Maximus Rex, Dragons flight, Saltine, Tempshill, Omegatron, Ed g2s, Head, Thue, Spikey, Traroth, Bloodshed- der, Secretlondon, Jerzy, Flockmeal, GPHemsley, Lumos3, Denelson83, Chuunen Baka, Donarreiskoffer, Branddobbe, Robbot, Ke4roh, Sander123, ChrisO, Korath, Chris 73, Dirgela, R3m0t, Naddy, Academic Challenger, Puckly, Rursus, Hemanshu, Hadal, JackofOz, Lupo, HaeB, Cyrius, Dina, Robert Happelberg, Psb777, ShutterBugTrekker, Nephelin, Giftlite, DocWatson42, Christopher Parham, Marnanel, Djinn112, Awolf002, Jyril, Harp, Inter, Wolfkeeper, Rbs, Obli, Sage Erk, Bradeos Graphon, Peruvianllama, Wwoods, Everyking, No Guru, Maha ts, Curps, Michael Devore, JamesHoadley, Cantus, Waltpohl, BrendanRyan, Macrakis, Python eggs, SWAdair, Edcolins, Golbez, Peter Ellis, ChicXulub, Auximines, Patteroast, Alexf, Geni, J, CryptoDerk, Antandrus, The Singing Badger, HorsePunchKid, Beland, Mis- fitToys, Vanished user 1234567890, Melikamp, PDH, Jossi, Rdsmith4, Mzajac, Tomruen, Satori, Icairns, Egan Loo, Marcos, Asbestos, Urhixidur, Edsanville, Trilobite, Adashiel, Grunt, Mike Rosoft, Simonides, Freakofnurture, Neckelmann, JTN, A-giau, Moverton, Dis- cospinster, Rich Farmbrough, Guanabot, Supercoop, Vsmith, Silence, ArnoldReinhold, Ponder, MuDavid, Pavel Vozenilek, Paul August, SpookyMulder, Panoramastitcher, Bender235, ESkog, Neurophyre, Kbh3rd, Kaisershatner, Petersam, JohnLynch, Brian0918, RJHall, Ylee, Project2501a, El C, Lankiveil, Joanjoc, Kwamikagami, Worldtraveller, Aude, Shanes, Tom, Remember, Sietse Snel, Art LaPella, RoyBoy, Femto, Bobo192, NetBot, Hurricane111, Aetherfukz, Smalljim, Olve Utne, Viriditas, Chessphoon, I9Q79oL78KiL0QTFHgyc, La goutte de pluie, Matt McIrvin, TheProject, BillCook, Sam Korn, Polylerus, Pearle, Gsklee, Jonathunder, Hooperbloob, Jjron, Eddideigel, Mareino, Wayfarer, KeesCook, Stephen G. Brown, Bob rulz, Alansohn, Gary, Burzum, Andrew Gray, A.T.M.Schipperijn, El stiko, Riana, Lectonar, Lightdarkness, Mac Davis, Mysdaao, Spangineer, Snowolf, Ross Burgess, Icewolf34, BRW, Tony Sidaway, CloudNine, Drat, Sciurinæ, Inge-Lyubov, LFaraone, Humble Guy, Kusma, Reaverdrop, Gene Nygaard, Dan East, HenryLi, Kazvorpal, Kitch, Ericl234, Gate- waycat, Stephen, Siafu, Dracogen, WilliamKF, Rorschach, Firsfron, TigerShark, LOL, Tom Ameye, Uncle G, BillC, Madchester, MONGO, Bennetto, Schzmo, Gengiskanhg, Bbatsell, Pufferfish101, Sengkang, Eyreland, SDC, Brendanconway, とある白い猫, Alec Connors, LinkTiger, Smartech, Dysepsion, MrSomeone, Aarghdvaark, Graham87, KyuuA4, Magister Mathematicae, Galwhaa, FreplySpang, Eteq, NebY, Icey, , Josh Parris, Pentawing, Canderson7, Drbogdan, Akubhai, Sjakkalle, Rjwilmsi, Koavf, Vary, Rgerhards, BlueMoonlet, JHMM13, Tawker, Mike Peel, Kazrak, HappyCamper, Bhadani, OKtosiTe, Yamamoto Ichiro, Marsbound2024, Titoxd, SchuminWeb, Mumblingmynah, RobertG, Dan Guan, Doc glasgow, Latka, Dave1g, Crazycomputers, Avalyn, Nivix, Shadow007, RexNL, Gurch, Brim- cmike, Arctic.gnome, TeaDrinker, Srleffler, Le Anh-Huy, Phoenix2, King of Hearts, Urzeitlich, Chobot, DaGizza, Mordicai, DVdm, Gw- ernol, E Pluribus Anthony, Wjfox2005, Wavelength, TexasAndroid, Spacepotato, RattusMaximus, Kinneyboy90, Hairy Dude, TSO1D, Jimp, Brandmeister (old), Kymacpherson, Prometheus235, RussBot, Zafiroblue05, Chuck Carroll, CanadianCaesar, Hellbus, Stephenb, Gaius Cornelius, Oni Lukos, Wimt, Ugur Basak, NatureBoy, Shanel, NawlinWiki, Wiki alf, BGManofID, Daemon8666, Mike18xx, Test- tools, Grafen, NickBush24, Itisan, SivaKumar, RazorICE, Howcheng, Robchurch, Nick, Aaron Brenneman, Tjarrett, Xdenizen, Jryden, Chal7ds, Rmky87, Raven4x4x, Voidxor, Grafikm fr, Tony1, Zwobot, Syrthiss, T, Samir, DeadEyeArrow, PS2pcGAMER, CorbieVreccan, Fbergo, Darkfred, Wknight94, Mkns, Deville, Phgao, Zzuuzz, Kandrey89, Ageekgal, Nikkimaria, Lorenzo Braschi, JRawle, Zobovor, Rlove, JoanneB, Alasdair, MrBook, Brianlucas, CWenger, Kier07, Hurricane Devon, Wainstead, Echartre, Geoffrey.landis, JLaTondre, Wootini, Ybbor, Tarquin Binary, Katieh5584, Kungfuadam, GrinBot, Iago Dali, Serendipodous, Mejor Los Indios, DVD R W, CIreland, Bibliomaniac15, Crusty007, AndrewWTaylor, Caponer, Deuar, Sardanaphalus, Crystallina, A bit iffy, GrafZahl, SmackBot, Amcbride, Nihonjoe, KnowledgeOfSelf, Martin.Budden, Pavlovič, Blue520, Speight, Kilo-Lima, KocjoBot, Jagged 85, RlyehRising, EncycloPetey, Delldot, Paxse, Fnfd, HalfShadow, Onsly, Gilliam, Ohnoitsjamie, Hmains, Betacommand, Skizzik, Andy M. Wang, Weirdoactor, Val- ley2city, Saros136, Endroit, AstroMalasorte, Bluebot, Kurykh, Geneb1955, Persian Poet Gal, Pylori, MalafayaBot, Hibernian, Saturn7, DHN-bot, Roy Al Blue, EddieSegoura, Zsinj, Can't sleep, clown will eat me, John Hyams, CharlesJS, Mrwuggs, Rogpyvbc, Nixeagle, OSborn, Avb, Astrobhadauria, TheKMan, Aces lead, Rsm99833, Addshore, Whpq, Edivorce, Amazins490, SundarBot, Lathal, Krich, Cy- bercobra, Bowlhover, Nakon, T-borg, Theodore7, Metebelis, Gerph, Daniel bg, Mini-Geek, Battamer, Eynar, Jklin, Drc79, Wizardman, Glenn Browne, Zonk43, Ericl, S@bre, Salamurai, Sarfa, Plilja, SashatoBot, Dane Sorensen, Garywill, Nishkid64, CFLeon, Harryboyles, Attys, Axem Titanium, Dbtfz, Molerat, Vanished user 9i39j3, Kuru, John, WhiteCat, Scientizzle, Shirifan, Heimstern, Breno, Gardner.DJ, Benesch, JorisvS, Temple, JayMan, Minna Sora no Shita, Goodnightmush, Ocatecir, Jess Mars, PseudoSudo, Ckatz, The Man in Ques- tion, RandomCritic, OzOz, Slakr, Werdan7, Tac2z, Mr Stephen, Godfrey Daniel, SandyGeorgia, Tuspm, Artman40, Ryulong, RichardF, AEMoreira042281, Elb2000, Jose77, Atakdoug, Darry2385, Johnny 0, Hu12, Politepunk, Michaelbusch, Dekaels, Vespine, Laurens-af, Joseph Solis in Australia, Shoeofdeath, Newone, StephenBuxton, Joao.caprivi, TurabianNights, Espi, Courcelles, Tawkerbot2, Bubbha, Cryptic C62, Poolkris, Lavaka, Orangutan, MightyWarrior, SkyWalker, Dia^, J Milburn, Spacini, JForget, GeneralIroh, CmdrObot, Tan- thalas39, Ale jrb, Dycedarg, Morganfitzp, KyraVixen, Drinibot, DeLarge, Charvex, Ruslik0, Benwildeboer, Dgw, AshLin, Lazulilasher, WeggeBot, Some P. Erson, Moreschi, MrFish, Myasuda, RagingR2, Ufviper, Cydebot, Nbound, Nebular110, -S TANK-, Stilwebm, Mike Christie, Steel, Evm123, Michaelas10, Gogo Dodo, Carl Turner, Travelbird, Bazzargh, ST47, Porsche997SBS, Grinning Fool, Master son, Tdvance, Tawkerbot4, Demomoke, DumbBOT, Chrislk02, FastLizard4, Bryan Seecrets, Ssilvers, Sockr44e, Omicronpersei8, Uber- ScienceNerd, ArminHammer, Casliber, Croocroo123, Thijs!bot, Pajz, Jordan11111, LeeG, Kablammo, Keraunos, Andyjsmith, Pampas 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 123

Cat, Young Pioneer, Oliver202, Headbomb, Dayn, John254, Neil916, Kathovo, Topquark170GeV, Cool Blue, Lars Lindberg Christensen, Davidhorman, The Proffesor, E. Ripley, CielProfond, Pcbene, Lithpiperpilot, BlytheG, Big Bird, RaNdOm26, Dawnseeker2000, Na- talie Erin, SomeHuman, Futurebird, Eleuther, Spud Gun, AntiVandalBot, Yupik, Luna Santin, Yr41193, Seaphoto, 105706, Peter50, Dpmcnevin, Quintote, DarkAudit, Dr. Submillimeter, Gdo01, Spencer, SkoreKeep, Altamel, Cbrodersen, Myanw, Uchohan, PresN, JAnDbot, Dan D. Ric, Deflective, MER-C, CosineKitty, LoveCowboy2024, Andonic, Igodard, Hut 8.5, Rentaferret, Rothorpe, Deni- madept, Acroterion, SteveSims, WolfmanSF, Murgh, Bongwarrior, VoABot II, AuburnPilot, Wikidudeman, JNW, SpazKitty, Repoed2, -Bigdan201, CTF83!, Diego bf109, Jespinos, Michele123, Twsx, Midgrid, Jkake, Than217, Catgut, Panser Born, PIrish, Ani ,باسم mum, Cyktsui, BatteryIncluded, ArthurWeasley, Gruby22, Loonymonkey, BilCat, Hamiltonstone, Allstarecho, Thehalfone, SpaceGuide, Pha0001, Shijualex, DerHexer, Edward321, WLU, Patstuart, Info D, WildRichLord, Revcph1958, Kheider, Pikolas, Gwern, NatureA16, Gjd001, MasterRadius, MartinBot, GM11, Racepacket, Arjun01, Poeloq, Rettetast, Roastytoast, Ambi Valent, Knayil, Averross, Ryan dude200, CommonsDelinker, Oysta, AlexiusHoratius, Pbroks13, PrestonH, Redian, Watch37264, J.delanoy, Pharaoh of the Wizards, DrKiernan, Trusilver, Svetovid, Asqwce, Ali, Lizrael, Hans Dunkelberg, Nigholith, Ginsengbomb, Clilly, KeybladeSephi, Kudpung, Gzkn, ABTU, St.daniel, Bot-Schafter, Gman124, Dfoofnik, Langara College, Gurchzilla, AntiSpamBot, (jarbarf), Berserkerz Crit, SuzanneKn, Hut 6.5, Belovedfreak, Blackvanillasky, Bushcarrot, NewEnglandYankee, Aquatics, Sculptorjones, Enguarde, Fjbfour, Potatoswatter, MetsFan76, Cmichael, Yoyo01, Cometstyles, WJBscribe, Aminullah, Tygrrr, SBKT, Aucahuasi, King Toadsworth, Mike V, Redrocket, Songjin, Kvdveer, Pdcook, Jarry1250, Jerry106, Legend=me, Idioma-bot, V vangipuram, Redtigerxyz, Black Kite, Lights, PeaceNT, Deor, VolkovBot, CWii, Johan1298, Jlaramee, Claudia rocks, SarahLawrence Scott, AlnoktaBOT, HeckXX, Toddles29, Rutherfordjigsaw, Katy- didit, Boaex, Philip Trueman, Jjpulczinski, TXiKiBoT, SwiftAce, Pyromaniaque, Malinaccier, Qaletaqa, Alanspence, GDonato, Miranda, Ann Stouter, Z.E.R.O., DocGratis, Paulfrank523, Qxz, Piperh, DennyColt, Bass fishing physicist, MasterSci, Leafyplant, Voiceofrea- son01, Sanfranman59, Happy2bback2, Abdullais4u, DoktorDec, Wassermann, Seb az86556, Ollige, Cremepuff222, Bearian, Rzhevski, CO, Pious7, Killing sparrows, MacTire, Rusica9231, Meesheek, Angrymansr, Synthebot, Su37amelia, Strangerer, Lovlymaddie, Mar vin , Patyoda, WatermelonPotion, Insanity Incarnate, Hinomaru kun, Sue Rangell, AlleborgoBot, Legoktm, NHRHS2010, EmxBot, Tedstryk, SquallLeonhart ITA, D. Recorder, Jk lol haha, Mehungy, ColinKelly, Moonmayne21, Guambomb, SieBot, Chronic Stoned Emo Ranger, Jim77742, Gtownhoyas34, PlanetStar, Tiddly Tom, Dwadejames03, Graham Beards, Scarian, Malcolmxl5, BotMultichill, ToePeu.bot, Oldag07, Gerakibot, Tonyvz, Miaie, Dawn Bard, Caltas, Overachievers, Universe=atom, Sk8drummerd, Mvierow, Lucas- bfrbot, Iamdaddysgirl, Rach-ach, Normz, WildWildBil, GlassCobra, Yulu, Purbo T, Kayla Norris, Liltlover, Purplepickle10, Keilana, RadicalOne, Tiptoety, Radon210, Editore99, Oda Mari, Mimihitam, Oxymoron83, BartekChom, 2djay7, KPH2293, Hello71, Steven Zhang, Lightmouse, Poindexter Propellerhead, Kcrocetti, Murlough23, Astrale01, Voltron, BenoniBot, YMama, Kudret abi, Freescrues, LonelyMarble, Torchwoodwho, Mojoworker, Rocksanddirt, Anyeverybody, Trashbird1240, Driftwood87, Dabomb87, Neo., Nergaal, C0nanPayne, Raasgat, Wjmummert, Velvetron, Tatterfly, ImageRemovalBot, Athenean, Yeah01011, Faithlessthewonderboy, Martarius, Stuart7m, ClueBot, LAX, PipepBot, Mroctoberfest, Fyyer, Foxj, The Thing That Should Not Be, Swapnils2106, Jan1nad, Wwheaton, Jesterrx, Teggstar1998, Higgins403, SuperHamster, ANSIFY 303, CounterVandalismBot, Laylarockmisocks, EconomicsGuy, Blanchardb, Igotmesomebathinapes, TarzanASG, Piledhigheranddeeper, Neverquick, Lampofdoom, DragonBot, Meweee, Excirial, Pumpmeup, Tony- Ballioni, Mandtplatt, Vivio Testarossa, Sun Creator, Jotterbot, PhySusie, Ember of Light, SockPuppetForTomruen, Bennyvk, BOTarate, Thingg, Darren23, Aitias, Greendog624, Alexkerkove, MelonBot, Lethalstrike5, ClanCC, Thikr, Arianewiki1, XLinkBot, Tylerluvsthevag, Forever unkown, Dark Mage, Mattrave, Sanjay517, Andrew Hing, Locoshonmachon, Tegles, Baileyboo1230, BOBBYFATSO, Thevyan, Thetwizzler150, Veenluk, Trevaqueline Mitchand, Ririri, JinJian, MystBot, Parejkoj, Koraki, Nerd geek, Sandman 445sss, Kbdankbot, Frenchyfrog, Brclarke, Hawkania, Ryryz666, Cbrooks91671, Kenpachi872, Threechanger, AVand, Some jerk on the Internet, Lol vandal 992, Lagus970, Talbballer, Bkhreal, DOI bot, SakuraKaira, Biggins96, Ronhjones, Mac Dreamstate, Heremod, Aselfcallednowhere, Ka Faraq Gatri, Kwer.rewk, Ccacsmss, Glane23, Chzz, Debresser, LinkFA-Bot, 5 square, 84user, Numbo3-bot, DubaiTerminator, Teles, Ettrig, Webwizard, Ben Ben, Luckas-bot, Yobot, Ptbotgourou, KamikazeBot, Dmarquard, AnomieBOT, Thuvan Dihn, Erdunbar, A More Perfect Onion, Archon 2488, SaiyanEmperor2008, Bsimmons666, Jim1138, Materialscientist, Citation bot, E2eamon, GB fan, ArthurBot, Xqbot, Link dude177, Timir2, Smk65536, KuRiZu, Werner65, Mlpearc, Srich32977, Almabot, Arsia Mons, GrouchoBot, Nayvik, Ataleh, ,Amaury, Charvest, Mangst, Shadowjams, Dico Calingal, Fotaun, Thehelpfulbot, FrescoBot ,قلی زادگان ,Hallen455, RibotBOT, SassoBot Dogzrule101, LucienBOT, Originalwana, Ceciliarozzie, Tobby72, Io Herodotus, Lookang, KokkaShinto, WarpCode, Goodbye Galaxy, Qfissler, HJ Mitchell, Louperibot, OgreBot, Kobrabones, Pinethicket, I dream of horses, HRoestBot, Tom.Reding, MJ94, RedBot, Σ, For- ward Unto Dawn, IVAN3MAN, Lightlowemon, FoxBot, Double sharp, TobeBot, Trappist the monk, Mrauscher, Orb85750, Rickky678, Vrenator, Krusberg, Aoidh, Seahorseruler, Diannaa, Stephen MUFC, ThinkEnemies, Suffusion of Yellow, Tbhotch, Minimac, Reepy1, DARTH SIDIOUS 2, Ashishindemand, RjwilmsiBot, HxCUNstopABLE, Burmiester, DASHBot, Mr. Anon515, EmausBot, John of Read- ing, Tuankiet65, WikitanvirBot, Cbornmann, Racerx11, GoingBatty, Gwillhickers, Jmencisom, K6ka, P. S. F. Freitas, ZéroBot, John Cline, Fæ, Josve05a, A2soup, EdEColbert, Dffgd, Access Denied, Hevron1998, H3llBot, Wiooiw, Cline92, Wayne Slam, RaptureBot, L1A1 FAL, Δ, Brandmeister, Inimbrium, Stephenj642, L Kensington, Victor98, MonoAV, Donner60, Breebreebjg, Sailsbystars, ChuispastonBot, Camero09, Hylian Auree, LikeLakers2, GrayFullbuster, Sven Manguard, DASHBotAV, Pook261998, Gary Dee, Splush23, ClueBot NG, Haromonos.haromonos3, TheWord77, Gilderien, Satellizer, Bobtedd123, KDS444, Beth.chattin, Xession, Loginnigol, Lanthanum-138, All Hail Hypnotoad!, O.Koslowski, Rezabot, SenseiAC, Widr, Danim, SentientSystem, Voldemortal, Diyar se, Helpful Pixie Bot, Bibcode Bot, Lowercase sigmabot, Pine, MKar, MusikAnimal, SpaceChimp1992, Frze, AvocatoBot, Mark Arsten, Cadiomals, Writ Keeper, Hari- zotoh9, Tycho Magnetic Anomaly-1, Colinmartin74, WikiAnaUser., Ubiquinoid, Nelg, Carliitaeliza, Hansen Sebastian, Plutoniumjesus, ChrisGualtieri, Soulparadox, Kelvinsong, Dexbot, KDaxs, Anderson, Lugia2453, Sidelight12, Omgpoo, 93, Max14182000, JustAMug- gle, Jake zahnzinger, Reatlas, Joeinwiki, Haribo2000, PinkAmpersand, Reed92, Bowwow828, Sreek123, Pink699, Fuhfue, Jcpag2012, 2001littlekaty, Runar98, Chetan8945, Albow7, Stub Mandrel, Kelleynoah123, Zenibus, Mirvworks, Antn123, Flygonfan42, John123456jk, Blackfire123, Ginsuloft, Exoplanetaryscience, Asherdancemachine, Heatfan9876, Theblogman44, Kn1467, Cancina5645, PlayStation 14, Monkbot, Dogov, Plokmijnuhbygvtfcdxeszwaq, Spiderjerky, Tetra quark, Isambard Kingdom, FlorZi, TheWhistleGag and Anonymous: 1550

• Uranus Source: http://en.wikipedia.org/wiki/Uranus?oldid=651174965 Contributors: RjLesch, Derek Ross, Lee Daniel Crocker, Brion VIBBER, Vicki Rosenzweig, Mav, Bryan Derksen, Malcolm Farmer, -- April, Ed Poor, Amillar, Andre Engels, Eob, Scipius, Danny, XJaM, JeLuF, Christian List, PierreAbbat, William Avery, SimonP, Ramin Nakisa, Fonzy, Spiff, Frecklefoot, Michael Hardy, Tim Star- ling, Oliver Pereira, DopefishJustin, Bobby D. Bryant, Ixfd64, Delirium, Minesweeper, Alfio, Egil, Looxix, Ahoerstemeier, Notheruser, Mark Foskey, Julesd, Glenn, Poor Yorick, Netsnipe, Andres, Evercat, Gh, Mxn, Ilyanep, Schneelocke, Hike395, Charles Matthews, Timwi, Wikiborg, Doradus, Tpbradbury, Ed g2s, Head, Traroth, Bloodshedder, Raul654, Dysfunktion, Wetman, Jerzy, Northgrove, Donar- reiskoffer, Branddobbe, Robbot, Juro, Dale Arnett, Fredrik, Tomchiukc, RedWolf, Naddy, , Merovingian, Zulugrid, Rursus, Timrollpickering, Bkell, Hadal, Robinh, Dina, Radagast, Robert Happelberg, Snobot, ShutterBugTrekker, Nephelin, Giftlite, DocWat- son42, MPF, Marnanel, Djinn112, Awolf002, Jyril, Oberiko, Gil , Harp, Wolfkeeper, Nunh-huh, Tom harrison, Monedula, Pe- ruvianllama, Wwoods, Everyking, No Guru, Curps, Michael Devore, JamesHoadley, MingMecca, Thetorpedodog, Niteowlneils, Bren- 124 CHAPTER 7. VENUS

danRyan, Python eggs, DÅ‚ugosz, Bobblewik, Golbez, Wmahan, ChicXulub, Steuard, Patteroast, Alexf, Gdm, Sonjaaa, Antandrus, The Singing Badger, HorsePunchKid, Mustafaa, Beland, Vanished user 1234567890, Jossi, Rdsmith4, Kesac, DragonflySixtyseven, Satori, Icairns, Arcturus, Gscshoyru, Asbestos, Martin.komunide.com, Neutrality, Urhixidur, Edsanville, Ensrifraff, Positron, Jcw69, Laisak, Adashiel, Trevor MacInnis, Mormegil, Freakofnurture, JTN, Nido, Discospinster, Rich Farmbrough, Guanabot, C12H22O11, Vsmith, ArnoldReinhold, Will2k, Wadewitz, MuDavid, Paul August, SpookyMulder, Night Gyr, Bender235, ESkog, Kbh3rd, Joeconsumer, The Iconoclast, Kalel, Loren36, Violetriga, Brian0918, RJHall, Sfahey, El C, Lankiveil, Kwamikagami, future, Gnomz007, Pila- tus, Worldtraveller, Aude, Shanes, Tom, Mavhc, Remember, Art LaPella, Cacophony, Femto, Thunderbrand, Jpgordon, Iridia, Adambro, Marco Castellani, Causa sui, Bobo192, Circeus, NetBot, Longhair, Hurricane111, Apollo2011, Smalljim, Dreish, Olve Utne, Elipongo, I9Q79oL78KiL0QTFHgyc, Sasquatch, MrInitialMan, BillCook, Maxl, Pharos, Gsklee, Kvaks, Xen0phile, Vesal, Cyrloc, Storm Rider, Bob rulz, Alansohn, JYolkowski, Anthony Appleyard, SnowFire, Chris16447, Polarscribe, Borisblue, Atlant, Keenan Pepper, Andrew Gray, Riana, AzaToth, Yamla, Axl, Lightdarkness, Mailer diablo, InShaneee, Dark Shikari, Mysdaao, Malo, VladimirKorablin, Bart133, Snowolf, Radical Mallard, Keepsleeping, Crobzub, Suruena, Luspari, Evil Monkey, Harej, Tony Sidaway, Inge-Lyubov, Mikeo, Itsmine, Versageek, Gene Nygaard, HenryLi, Kazvorpal, WilliamKF, Novacatz, Kelly Martin, Rorschach, Jeffrey O. Gustafson, OwenX, Georgia guy, Ugo, Benhocking, TomTheHand, BillC, Kzollman, Commander Keane, MONGO, Kelisi, Schzmo, Sengkang, Red Dalek, Eyreland, Prashanthns, Alec Connors, Smartech, Rnt20, Graham87, Marskell, Deltabeignet, Magister Mathematicae, BD2412, FreplySpang, RxS, MechanicallySeparatedChicken, NebY, BorgHunter, Pentawing, Sjakkalle, Rjwilmsi, Koavf, Joffan, Urbane Legend, Rillian, BlueMoon- let, Tangotango, Sdornan, Tawker, Mentality, Mike s, Mike Peel, Sajad.Ghafarzadeh, Kazrak, Tewilliams, Ligulem, Bhadani, Ttwaring, Kaktuse, Knave7, Ucucha, Maurog, Jbamb, Sango123, Yamamoto Ichiro, N0YKG, Roo60, Titoxd, Sugury, Goclenius, FlaBot, Washing- ton Irving, Akiss, RobertG, Old Moonraker, Nihiltres, Nivix, RexNL, Gurch, ChongDae, Arctic.gnome, DannyZ, Str1977, TeaDrinker, Joedeshon, Srleffler, Jester92, King of Hearts, Chobot, Flying , ChiTrek, Gwernol, EamonnPKeane, The Rambling Man, YurikBot, RobotE, Sceptre, Vlad4599, Anonymous editor, Teneyesone, Bergsten, SpuriousQ, CanadianCaesar, Hellbus, Ori.livneh, Stephenb, Rin- trah, Polluxian, Mike Young, Merlincooper, Kimchi.sg, Wimt, Lusanaherandraton, NawlinWiki, Bulbabean, Wiki alf, Deskana, Jaxl, Kvn8907, Mmccalpin, Harksaw, Howcheng, FFLaguna, Dureo, Lexicon, Nick, Retired username, Jamesd, Brandon, Chal7ds, Raven4x4x, Lomn, Zwobot, Ospalh, T, WMarsh, Bota47, Darkfred, Wknight94, Ms2ger, Virtuini, Tuckerresearch, FF2010, TheSeer, 21655, Poppy, Zzuuzz, Ufpncc1965, Chesnok, Kandrey89, Ageekgal, Chaos syndrome, Richard s, Theda, Fang Aili, Pb30, Th1rt3en, Opes, Chris Brennan, Mastercampbell, Aeon1006, Kier07, Hurricane Devon, Rocketrye12, Emc2, ArielGold, RunOrDie, Bly1993, Kungfuadam, Maxamegalon2000, Paul Erik, Gmrepoli, GrinBot, Iago Dali, Rehevkor, Hawkeyef, SkerHawx, Serendipodous, Victor falk, Caponer, Deuar, Sardanaphalus, Sintonak.X, A bit iffy, SmackBot, Espresso Addict, Saravask, Bobet, Cdogsimmons, Prodego, KnowledgeOf- Self, Royalguard11, VigilancePrime, Alex1011, Gnangarra, Unyoyega, Pgk, Phaldo, Jacek Kendysz, Kilo-Lima, Bmearns, EncycloPetey, BPK2, Delldot, Ribbet32, LuciferMorgan, Veesicle, ZeroEgo, Sedonaarizona, Edgar181, Shai-kun, Commander Keane bot, Xaosflux, Aksi great, Richmeister, Gilliam, Hmains, Ghosts&empties, Skizzik, Superpig56, Saros136, CanbekEsen, Bluebot, Kurykh, Philosopher, Geneb1955, Dr bab, Mokwella, Rick7425, Silly rabbit, SchfiftyThree, Hibernian, Moshe Constantine Hassan Al-Silverburg, Vanessadan- nenberg, Dlohcierekim's sock, Wrxsti fan, DHN-bot, [email protected], Mkamensek, Gracenotes, Reaper X, JohnWhitlock, Zsinj, Can't sleep, clown will eat me, Mrwuggs, LC Revelation, Astringer, Astrobhadauria, Thisisbossi, Chan Yin Keen, Jackmitchell, Krsont, Addshore, Edivorce, Monacat, Nasty Dick, Krich, PrometheusX303, Cybercobra, Nakon, Jiddisch, J450NH3,“alyosha”, Dread- star, Astroview120mm, Illnab1024, DMacks, Drc79, Zonk43, Kotjze, Gruznov, N Shar, Zedall, Noobycheese, Risker, Jtm71, Vina-iwbot, Pilotguy, Kukini, SashatoBot, Esrever, CFLeon, Rory096, Erimus, Harryboyles, Srikeit, Dbtfz, Vanished user 9i39j3, Kuru, John, Drahcir, Buchanan-Hermit, Moleskin, JohnCub, Mrlopez2681, Sir Nicholas de Mimsy-Porpington, Linnell, Shadowlynk, JoshuaZ, JorisvS, Tem- ple, JayMan, Mgiganteus1, Goodnightmush, Kistler91, Mr. Lefty, IronGargoyle, Jess Mars, Keber, Retromaniac, Ckatz, RandomCritic, A. Parrot, Slakr, Kyoko, Feureau, Waggers, SandyGeorgia, Funnybunny, Dhp1080, Ryulong, TPIRFanSteve, Gazjo, RichardF, Elb2000, Jose77, Nakedcellist, 96hixjoh01, Wwagner, Soxrock, ThuranX, Esoltas, Ossipewsk, ILovePlankton, K, Michaelbusch, Dekaels, The Gi- ant Puffin, Joseph Solis in Australia, LandruBek, Newone, Gheuf, KsprayDad, Tony Fox, Richard75, Blehfu, Shikyo2, Az1568, Yoy- opro5, Tawkerbot2, Dlohcierekim, Poolkris, Merryjman, Ioannes Pragensis, JForget, Thedemonhog, SpaceHouse, CmdrObot, Geremia, Robin Scagell, Dycedarg, Scohoust, Makeemlighter, SupaStarGirl, SaintCahier, Vyznev Xnebara, Rwflammang, Drinibot, Ruslik0, Ben- wildeboer, Juhachi, Outriggr, MarsRover, WeggeBot, Logical2u, Avillia, Tex, RagingR2, Ufviper, AndrewHowse, Cydebot, Stebbins, Natasha2006, IvarSnaaijer, Nbound, Ryan, Metacosm, -S TANK-, Dominicanpapi82, DrunkenSmurf, SyntaxError55, Gogo Dodo, JFree- man, Flowerpotman, Corpx, ST47, Pgk4, Wikipediarules2221, Caliga10, Tawkerbot4, Christian75, Codetiger, DumbBOT, Chrislk02, ,Rab V, Casliber, Thijs!bot, LeeG, Davidelit, Volucris, Keraunos, Andyjsmith, Headbomb ,הסרפד ,Gonzo fan2007, Voldemortuet, UV LordKrishna, Marek69, WillMak050389, James086, Yettie0711, Lars Lindberg Christensen, Davidhorman, The Proffesor, AgentPepper- mint, Blathnaid, RaNdOm26, Natalie Erin, Lamy999, Escarbot, Mentifisto, Porqin, AntiVandalBot, Yupik, Khing, AbstractClass, Ma- jorly, Gamedude41, Luna Santin, Jmsevits, Ricnun, Nugget-92, Opelio, DragonBlazer57, Exteray, Podolakj, Dr. Submillimeter, Diver dude2, DarthShrine, Spouima, SkoreKeep, Firiun, Cbrodersen, Myanw, PresN, Gökhan, Kariteh, DOSGuy, JAnDbot, Deflective, Husond, PopsHunsinger, Mikerobe007, Barek, MER-C, BlindEagle, Planetary, Something14, Hello32020, ThanosMadTitan23, Andonic, Dcooper, Igodard, Natureguy1980, Roleplayer, Hut 8.5, 100110100, Rentaferret, Savant13, Dermann69, Kirrages, Rothorpe, LittleOldMe, .anacond- abot, Acroterion, SteveSims, Bencherlite, Achero, Meeples, Pablothegreat85, Magioladitis, WolfmanSF, Murgh, Bongwarrior, VoABot II, --Rivertorch, Bigdan201, CTF83!, Jonte ,باسم ,AuburnPilot, Wikidudeman, MJD86, Davidjk, Hasek is the best, Frip1000, Mbc362 , I ain't JtV, SparrowsWing, Midgrid, Indon, Animum, Cyktsui, ArthurWeasley, Allstarecho, Styrofoam1994, Mike Payne, Chris103, St.Jimmy666, Shijualex, Just James, Denmer, DerHexer, JaGa, Megalodon99, Lelkesa, Strider01, Doesper, Lost tourist, Revcph1958, Spacew00t, Kheider, PsyMar, Soderpoppers, Hdt83, MartinBot, FlieGerFaUstMe262, Tooter Shellby, BetBot, Ben MacDui, Rettetast, Ravichandar84, Ambi Valent, CommonsDelinker, AlexiusHoratius, Bgold4, Lilac Soul, Ducksauce101, Trew.Trew, Dinkytown, Kath- lyn.Price, Nerablade, AlphaEta, Jameswheeler, Watch37264, J.delanoy, DrKiernan, Nate1028, Skeptic2, AstroHurricane001, AAA!, Lizrael, BillWSmithJr, Think777, Hans Dunkelberg, Piercetheorganist, All Is One, Jameswheeleratskool, Nigholith, Eliz81, MogWV, Extransit, Bobo bobo, WarthogDemon, Colew130, ABTU, Acalamari, Rc3784, JVSmithson, Katalaveno, DarkFalls, Gman124, Cromdog, AntiSpamBot, Michael Patrick Wilson, GhostPirate, Raining girl, NewEnglandYankee, SJP, Touch Of Light, MKoltnow, Toon05, Mas- terbutt, Wcnghj, Juliancolton, Cometstyles, WJBscribe, RB972, Jonnyhexenpl, U.S.A.U.S.A.U.S.A., Vanished user 39948282, Arvind Vyas, Guyzero, Bonadea, Divad89, JavierMC, Zeosurfer, Corona3, Piepoop, Halmstad, Idioma-bot, Zeostar, Xnuala, Redbombtoma, Wikieditor06, Lights, Chinneeb, VolkovBot, Lanoshockomwano, IWhisky, Thedjatclubrock, Johan1298, DagnyB, RingtailedFox, Nbur- den, Alexandria, AlnoktaBOT, Toddles29, Katydidit, Aesopos, Barneca, Philip Trueman, Craigmontvii, TXiKiBoT, SwiftAce, Qale- taqa, Qdaman, TheresJamInTheHills, Rei-bot, Ann Stouter, Z.E.R.O., Anonymous Dissident, Mushroomfart, Qxz, Eriko-nee, MasterSci, Sirkad, Psyche825, Seb az86556, Cremepuff222, Jmpenzone, Ranger1524, Onore Baka Sama, Maxim, Damërung, Orange-kun, Knight- shield, Jclarine, MooCowWow, Mikeandrich, Pious7, Lerdthenerd, Enigmaman, Josehunder, Constantine Gorov, Masterchi101, Halois- cool, Lerolock, Synthebot, Novena, SmileToday, Falcon8765, Burntsauce, Osimi11, Coltman61, Zach21, Coopol, Bungo77, Spriteddude, Agentkro, Better time for the wiks, RinoaLockhart, AlleborgoBot, Funeral, Logan, DThaler, Dkang00, Mizz.Smarty, Bruce699696, Chick- 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 125

magnet92, Tvinh, Thierryhenry14legend, Samm79, NHRHS2010, Oklabama, Jeodo, EmxBot, Mikepoop, LOTRrules, SieBot, Éiginnte, Coffee, Jim77742, PlanetStar, Tiddly Tom, OTAVIO1981, Caulde, Euryalus, BotMultichill, Hertz1888, Oldag07, Gerakibot, Parhamr, Caltas, Universe=atom, Triwbe, Smsarmad, Fieryo, Grndrush, TrulyBlue, Pushawboy595, Psychless, Barliner, WildWildBil, Purbo T, Matts118, Keilana, Darknut, Areya, Kolr, Jonathan Barrett, Gusk 24, Mickyicky, HilariousLaugh, Oda Mari, Arbor to SJ, Clarky2113, EastCoastPwnerz, Hahaha34, Gublefink, Fireboy992007, IFixx, Moonraker12, Oxymoron83, Skateboarderf2, Antonio Lopez, Ginger- man1234567, Fartsytartsy, Lightmouse, Dmsmischief, Littledude69, Murlough23, Deejaye6, BenoniBot, OKBot, LonelyMarble, Bake hi, William Saturn, Anyeverybody, Joshschr, C0nanPayne, Starcluster, Steve, Dlrohrer2003, Kanesue, ClueBot, LAX, Deviator13, Rumping, PipepBot, NonSequitar, Baseking2005, Madhab mitra, VQuakr, YabbaDabbaDubya, Fivepanthers, Shaye12345, Undersnout, Xavexgoem, Mpd1989, CounterVandalismBot, Niceguyedc, Captian 0bvious, Piledhigheranddeeper, Kellenoa, Riccomario96, 2muffins, DragonBot, Sethton, Rhamphorynchus, AssegaiAli, MEATwad407, Metallica-123, Sun Creator, AZatBot, Coinmanj, NuclearWarfare, Cenarium, Jot- terbot, Imsohood, Shagurl, Promethean, Ember of Light, Freunde, Nvvchar, Neji800, CowboySpartan, El planeto, Razorflame, Notturno, Kkarma, 1943lowes, Thehelpfulone, Jhannah100, Ninjirate009, Jamesmorrey, Thingg, Aitias, RegaL the Proofreader, Wertystorm, Co- coapuffst99, Weirdo813, Racistbassisthuckabee, Hiiamauser, One47, WraithJ, Benandscott, Theinvisbaleraver, 4moreyearsofdouchebag, DTFerry23, Dave612, The Ash Lad, Tylerbrooks, Ndoop, Versus22, Feces98, Notserpw, Forever unkown, Dark Mage, Swift as an Ea- gle, Mattrave, Mcrocks12, Anturiaethwr, Tegles, Eiaschool, Jordan591, Harlock81, NFRANGA, Hunt0h, NCDane, Kbdankbot, Cheezy boundy, Daniel tues, Mortense, Tighe, Lagus970, DOI bot, Tazbuc5, Rosscaldwell, Tattoo275, Tanhabot, Ilya-108, Luke$yme, Harrymph, Heremod, Ayrenz, Cypkerth, Ninjacat78, LaaknorBot, CarsracBot, Delaszk, Glass Sword, Roux, SamatBot, LinkFA-Bot, Numbo3-bot, Ehrenkater, Koliri, Krano, Funnydood123, Zekekromar, Luckas-bot, Yobot, Ptbotgourou, KamikazeBot, Kjaer, Mister Flash, AreaControl, Eric-Wester, Iplaypingpong, AnomieBOT, Roscom1888, Jakecarr678, Dwayne, Ramonesnumer1fan, JackieBot, Bomas Hawkins, Jok3r09, Gio band117, Icalanise, Puppet mastr, Visiting Guest, Materialscientist, Everton2kn8, The High Fin Sperm Whale, Citation bot, Strontium- Dogs, ArthurBot, Santa Claus of the Future, Hacker's union, MauritsBot, Xqbot, TinucherianBot II, Timir2, Phthinosuchusisanancestor, Jydog, TechBot, Smk65536, Gospodar svemira, DSisyphBot, Boltz6100, Mlpearc, Srich32977, Almabot, Shanman7, GrouchoBot, Ataleh, Frosted14, OSU1994, RibotBOT, SassoBot, Kyng, Enceladusgeysers, Jalapenos do exist, The Wiki ghost, Trafford09, Danielclarketerre- longe, Chaheel Riens, A. di M., Samwb123, BornInLeningrad, Fotaun, A.amitkumar, Admiral-multibrow, Dave3457, Fingerz, FrescoBot, Io Herodotus, Lookang, Garband10, Datye, HJ Mitchell, Neutiquam, 8, Citation bot 1, Kobrabones, Tintenfischlein, HRoestBot, Jonesey95, Tom.Reding, RedBot, Phearson, DReifGalaxyM31, Double sharp, TobeBot, Yunshui, Dinamik-bot, Extra999, Earthandmoon, Tbhotch, DARTH SIDIOUS 2, RjwilmsiBot, TjBot, Camo Drako, Ripchip Bot, Nmillerche, Burmiester, DASHBot, Karin127, EmausBot, Orphan Wiki, WikitanvirBot, Qurq, Gfoley4, Racerx11, 1Martin33, Jingle38, P. S. F. Freitas, HiW-Bot, ZéroBot, A2soup, Vengavenga, Nicolas Eynaud, AvicAWB, H3llBot, Rapture2018, Kyucasio, 3sdanog, Мл.научный сотрудник, L Kensington, Jguy, Jrichard2012, Spartylove, Sailsbystars, Lewis274, Puffin, Chinoblanco, Smartie2thaMaxXx, CGPGrey, Honesty First, ChuispastonBot, Ryanmagoo, Terra Novus, Whoop whoop pull up, Alcazar84, Dmp99, ClueBot NG, AlbertBickford, Brett2829, Derschmidt, Frietjes, Delusion23, Corusant, Kirklove, Castncoot, Helpful Pixie Bot, Msd2001, Gob Lofa, Bibcode Bot, Symbiboy, MKar, Ableblood, SpaceChimp1992, Gallina3795, Dotdotdotatsignapostrophe, Q6637p, Cadiomals, Denassq, Tycho Magnetic Anomaly-1, Colinmartin74, Louissegal2000, Wavyinfinity, Thanhtinsaosang, SoylentPurple, Bumbo1234, Rhlozier, Ekren, Dexbot, Br'er Rabbit, Blobbie244, Clockery, CorinneSD, JustAMuggle, Reatlas, Rfassbind, MarchOrDie, Epicgenius, Jcpag2012, Lindenhurst Liberty, B14709, SamX, 展翅飛翔, Transphasic, Thedrumsmasher, OccultZone, Jomey, Cancina5645, PlayStation 14, Monkbot, SkateTier, Trackteur, EricAnthony101, Spiderjerky, Tetra quark, Sol2y and Anonymous: 1234

• Venus Source: http://en.wikipedia.org/wiki/Venus?oldid=655942758 Contributors: NathanBeach, Brion VIBBER, Eloquence, Vicki Rosenzweig, Mav, Bryan Derksen, Zundark, The Anome, Taw, Jeronimo, Malcolm Farmer, -- April, Mark, Ed Poor, Aidan Elliott- McCrea, Amillar, Alex.tan, Andre Engels, Eob, Danny, XJaM, JeLuF, William Avery, SimonP, GrahamN, Fonzy, Dwheeler, Olivier, Rickyrab, Fransvannes, Rbrwr, Spiff, Seldon, Edward, Patrick, Infrogmation, Ken Arromdee, Michael Hardy, Tim Starling, Oliver Pereira, Lexor, Nixdorf, Ixfd64, Tango, Cyde, Minesweeper, Alfio, Kosebamse, Shimmin, Egil, Looxix, Ihcoyc, Mdebets, Ahoerstemeier, Snoyes, CatherineMunro, TUF-KAT, TUF-KAT, Angela, Mark Foskey, Glenn, Poor Yorick, Kwekubo, Evercat, Lancevortex, Mxn, Raven in Orbit, Schneelocke, Hike395, Hashar, Timwi, RickK, Stone, Andrewman327, Doradus, Haukurth, CBDunkerson, Robertb-dc, Tpbradbury, Drag- ons flight, Furrykef, Taxman, Ringomassa, Head, Samsara, Traroth, Anupamsr, Bloodshedder, Raul654, Wetman, BenRG, Jeffq, Owen, Lumos3, Phil Boswell, Robbot, MrJones, Celsius1414, Naddy, Modulatum, Smallweed, Chris Roy, Merovingian, Academic Challenger, Rursus, Geogre, Bkell, Hadal, UtherSRG, Wereon, Anthony, Peter L, Carnildo, ShutterBugTrekker, Nephelin, Centrx, Giftlite, Reuben- barton, Christopher Parham, Djinn112, Awolf002, Jyril, Sj, TOttenville8, Harp, Nichalp, Wolfkeeper, Tom harrison, Lupin, Herbee, Karn, Alterego, Everyking, Curps, Michael Devore, Henry Flower, Wikibob, Jackbrown, Joe Kress, Erdal Ronahi, Sdfisher, Gareth Wyn, Kainaw, Rchandra, Gzornenplatz, Matt Crypto, Python eggs, Jackol, Bobblewik, Cam, Wmahan, Infinitysnake, OldakQuill, ChicXulub, Gadfium, Andycjp, DocSigma, Alexf, Geni, Xmnemonic, Chris Edgemon, Yath, Antandrus, The Singing Badger, HorsePunchKid, Zaha, MisfitToys, Piotrus, Vanished user 1234567890, Kusunose, FelineAvenger, Rdsmith4, Samy Merchi, RetiredUser2, Tomruen, Icairns, B.d.mills, Neu- trality, Urhixidur, Edsanville, Irpen, Ukexpat, Fg2, JohnArmagh, Deglr6328, Chmod007, M1ss1ontomars2k4, Marnevell, Lacrimosus, Spiffy sperry, DanielCD, Ultratomio, EugeneZelenko, Indosauros, Mark Zinthefer, Discospinster, Rich Farmbrough, Avriette, Guanabot, BlueMars, Supercoop, FraKctured, Martin TB, Vsmith, Florian Blaschke, ArnoldReinhold, Rasmusdf, Ponder, D-Notice, Dbachmann, Mani1, Chrislee, MuDavid, Pavel Vozenilek, SpaceFrog, Bender235, NeilTarrant, Violetriga, Evice, Brian0918, RJHall, Ylee, Sfahey, El C, Fenevad, Huntster, Joanjoc, Kwamikagami, Evand, Worldtraveller, Tverbeek, Remember, Art LaPella, Femto, Adambro, Bobo192, Circeus, Smalljim, NightDragon, .:Ajvol:., ZayZayEM, Elipongo, Angie Y., Nesnad, Kappa, La goutte de pluie, Jojit fb, Timsheridan, BillCook, Sam Korn, Fwb22, Gsklee, A2Kafir, Jumbuck, Danski14, Bob rulz, Alansohn, Gary, Tablizer, Eric Kvaalen, Keenan Pepper, Moanzhu, Andrewpmk, Paleorthid, Andrew Gray, Sp82, Cbotman, AzaToth, Lectonar, Corwin8, JanSöderback, Mlm42, Hu, Avenue, DreamGuy, Snowolf, Mbloore, Velella, BanyanTree, Juan Toledo, Rebroad, Evil Monkey, RainbowOfLight, Inge-Lyubov, Cmapm, Zx- cvbnm, Gene Nygaard, Dan East, HenryLi, Tr00st, Leopard, Red dwarf, Adrian.benko, BerserkerBen, Duke33, Feezo, Siafu, Gmaxwell, WilliamKF, Angr, Rorschach, Mel Etitis, Woohookitty, Jannex, DonPMitchell, ChrisNoe, TigerShark, Ylem, MrNexx, Volcanopele, De- crease789, Plek, BillC, Bigfrozenhead, Chris Mason, Zealander, Bricktop, Nefertum17, MONGO, Eleassar777, Pi@k, Tabletop, Keta, Kelisi, Ch'marr, TotoBaggins, BartBenjamin, Cat11, Steinbach, X444, Sengkang, GregorB, CharlesC, Jon Harald Søby, Mayz, Oldel- paso, Prashanthns, Smartech, Teemu Leisti, Driftwoodzebulin, Cataclysm, Emerson7, MrSomeone, Paxsimius, Mandarax, Ashmoo, Gra- ham87, Marskell, JiMidnite, Johnny Mnemonic, Deltabeignet, Magister Mathematicae, TAKASUGI Shinji, FreplySpang, RxS, Pentawing, Jcmo, Canderson7, Funkymuskrat, Drbogdan, Akubhai, Rjwilmsi, Urbane Legend, Vary, Hiberniantears, JoshuacUK, Tawker, Mentality, Heah, Mike Peel, Crazynas, Bubba73, Boccobrock, AndyKali, Brighterorange, Afterwriting, Ttwaring, Wkruse, GregAsche, Sango123, DirkvdM, Dbigwood, Yamamoto Ichiro, FayssalF, Titoxd, Ian Pitchford, SchuminWeb, RobertG, Crazycomputers, Finsen, Nivix, RexNL, Gurch, Arctic.gnome, Enon, R Lee E, TeaDrinker, Alphachimp, Malhonen, Srleffler, DybrarH, Zotel, Gurubrahma, Glenn L, Kelpi, Phoenix2, King of Hearts, Chobot, Raincheerleader, Rewster, DVdm, PainMan, Mysekurity, Debivort, Cobaahema, Banaticus, Elfguy, Roboto de Ajvol, The Rambling Man, Satanael, Mercury McKinnon, TexasAndroid, Koveras, Deeptrivia, Jimp, RussBot, Kauffner, Fabar- 126 CHAPTER 7. VENUS

tus, Anonymous editor, Gspr, Witan, Qrasy, Hydrargyrum, Stephenb, Mithridates, Gaius Cornelius, CambridgeBayWeather, Cpuwhiz11, Kimchi.sg, Dorthonion, Bovineone, Wimt, Ebow, Anomalocaris, NawlinWiki, SEWilcoBot, Wiki alf, BGManofID, Itisan, Exir Kamal- abadi, RazorICE, Seegoon, Bmdavll, Irishguy, Brandon, Dppowell, Rmky87, Raven4x4x, Semperf, Tony1, Martinwilke1980, Wknight94, Noosfractal, Leptictidium, Manjithkaini, Bdell555, Mike Serfas, Show no mercy, 21655, Deville, Twintop, Zzuuzz, Chase me ladies, I'm the Cavalry, Closedmouth, Rpvdk, Pb30, KGasso, Acer, Shakil Mustafa, JoanneB, Symon, Fram, Hurricane Devon, Geoffrey.landis, HereToHelp, Kaippally, Wbrameld, Nixer, RunOrDie, Kungfuadam, Junglecat, Phr en, Iago Dali, Serendipodous, DVD R W, Caponer, Luk, Rayd8, Deuar, IslandHopper973, Sardanaphalus, Veinor, Sintonak.X, SmackBot, Mark Tranchant, KnowledgeOfSelf, Hydrogen Io- dide, Dodava, Lsorin, Jagged 85, Davewild, Thunderboltz, WookieInHeat, EncycloPetey, Jrockley, Jab843, Mdd4696, Lotse, ProveIt, Canthusus, TheDoctor10, Timsbleung, HalfShadow, JFHJr, PeterSymonds, Ema Zee, Gilliam, DividedByNegativeZero, Oscarthecat, Skizzik, Saros136, Amatulic, Master Jay, Keegan, JonRidinger, Geneb1955, Agateller, Quinsareth, Persian Poet Gal, Jlao04, Northern, Cbh, Anchoress, Hollow Wilerding, SchfiftyThree, Hibernian, No-Bullet, Ikiroid, Ctbolt, Baa, DHN-bot, [email protected], Sbharris, Darth Panda, Lewis007, Scwlong, Salmar, Can't sleep, clown will eat me, VJDocherty, DHeyward, Murder1, Mrwuggs, As- trobhadauria, Wikipedia brown, Krsont, Andy120290, Addshore, Kcordina, Edivorce, Rocksandfossils, Aldaron, Krich, Robma, Nakon, TMW, Dreadstar, Wjtimmerman, Mini-Geek, Hgilbert, Jan.Kamenicek, Polonium, Omnipotence, Adrigon, SpiderJon, MonkeyMumford, Zonk43, Risker, Ck lostsword, FelisLeo, NeilFraser, Sarfa, Ohconfucius, GoldenTorc, Thejerm, SashatoBot, Mksword, NormalGoddess, Kuru, Titus III, John, JanderVK, Drahcir, Jrothwell, Soumyasch, Linnell, JoshuaZ, Kreuzfeld, JorisvS, Temple, Scetoaux, IronGargoyle, SpyMagician, Jess Mars, Keber, Heliogabulus, Chrisd87, Ckatz, The Man in Question, RandomCritic, A. Parrot, Serpentinite, Beetstra, Stevebritgimp, Jhpace1, George The Dragon, Xiaphias, Don Alessandro, Tobyw87, Kliqjaw, Ryulong, Sims2789, RichardF, Novangelis, Elb2000, Jose77, Peyre, Floridan, Politepunk, Papertiger, BranStark, Iridescent, Majorbonkers, Michaelbusch, Alessandro57, Scooter20, Newone, J Di, Igoldste, Takarada, CapitalR, Ewulp, Mssgill, Tawkerbot2, Dlohcierekim, George100, Poolkris, Arhain, P-Chan, CalebNo- ble, Sarvagnya, Vjamesv, Gustavh, JForget, Adam Keller, VoxLuna, CmdrObot, Ale jrb, Geremia, TheHerbalGerbil, Memetics, Sasho84, Tuvas, BeenAroundAWhile, N3X15, Runningonbrains, MiShogun, BKalesti, Ruslik0, GHe, Orannis, CuriousEric, Dwolsten, MarsRover, Todowd, Joelholdsworth, WeggeBot, Moreschi, Borislav Dopudja, Nilfanion, Ufviper, Rudjek, Schauf, Icek, Badseed, Nbound, Domini- canpapi82, ArgentTurquoise, Steel, DrunkenSmurf, Vanished user vjhsduheuiui4t5hjri, Gogo Dodo, Red Director, Zginder, MattButts, JFreeman, Flowerpotman, Llort, Ykliu, Scooteristi, Rafeal, SakuraKitsune45, Tdvance, Tawkerbot4, DumbBOT, Chrislk02, YorkBW, Doc W, Paddles, Asenine, Robertinventor, Thenewestdoctorwho, Brad101, SteveMcCluskey, Sancort, Omicronpersei8, Cancun771, Theirish- pianist, Maat333, OakAve222, FrancoGG, Thijs!bot, Epbr123, Tepidpond, Interested2, Cassie, cole, Keraunos, Andyjsmith, Anthius, Halibut Thyme, Headbomb, Newton2, Ranger 1 (usurped), A3RO, HelenKMarks, Brichcja, Catsmoke, DoomsDay349, Grayshi, Nick Number, TangentCube, Dawnseeker2000, Natalie Erin, CTZMSC3, Northumbrian, Escarbot, KrakatoaKatie, AntiVandalBot, Yupik, MR 17, CommanderCool1654, Majorly, Yonatan, Luna Santin, Clarenceville Trojan, Ricnun, Opelio, MeNext, Dr. Submillimeter, Li- bLord, Farosdaughter, Jrizzy4, SkoreKeep, Aliwalla, Storkk, Myanw, PresN, Gökhan, JAnDbot, Deflective, Husond, MER-C, Skomorokh, CosineKitty, Nthep, Something14, Janejellyroll, Miltopia, Db099221, Sln3412, LGDubs, Andonic, Natureguy1980, Roleplayer, Rentafer- ret, Argent Cerulean, Who is like God?, Hardee67, Rothorpe, Sami assahli, FaerieInGrey, Tomst, WolfmanSF, Murgh, Suradasa, Bongwar- Think ,باسم ,rior, VoABot II, Sushant gupta, Bcsr4ever, Adam keller, Kuyabribri, Hasek is the best, JamesBWatson, Jerome Kohl, Eltener outside the box, Stotan, Lucyin, Bigdan201, Avicennasis, Wikiwhat?, Catgut, Panser Born, Spookiejjr, Cyktsui, ArthurWeasley, Arbeiter, Torchiest, 28421u2232nfenfcenc, BilCat, Joeloveslego, Jc1346729, MorningGrace, IanUK, AdoreMila, Just James, Glen, DerHexer, JaGa, Megalodon99, TheRanger, Markco1, Kheider, Gjd001, Oren0, Bmf 51, Cliff smith, Hdt83, MartinBot, Schmloof, FlieGerFaUstMe262, PAK Man, PatrickLMT, Vlink, Theodore141, Jim.henderson, Naohiro19, Rettetast, Jerry teps, Uriel8, R'n'B, CommonsDelinker, Alex- iusHoratius, Genesis12, Paranomia, Watch37264, J.delanoy, Pharaoh of the Wizards, Tinwelint, DrKiernan, Bogey97, DomBot, 16345, Uncle Dick, All Is One, Jameswheeleratskool, Mike.lifeguard, KrytenKoro, Anoushirvan, WarthogDemon, Thaurisil, Nemrac2, ABTU, Rod57, IdLoveOne, Vegasprof, Bot-Schafter, Katalaveno, McSly, Vandriel1325, Vineeth.vooppala, DJ1AM, Gurchzilla, Jancoop, (jar- barf), M-le-mot-dit, Mortbrew, WHeimbigner, NewEnglandYankee, Rominandreu, Fountains of Bryn Mawr, Gallador, Supersmell, SJP, Malerin, Salander86, Sopwith07, BigHairRef, Sunderland06, Myson45, Juliancolton, Haljackey, Cometstyles, Iamjasonyo, WJBscribe, Aaronbeemer, Burzmali, Gwen Gale, Zamonin, Natl1, LastChanceToBe, Belegur, Useight, Retal, Hork the Zombie, Gpetrov, NotoriousG, Xiahou, Squids and Chips, Dialashop, Idioma-bot, BradDeharder, Spellcast, Domoregan, Glossologist, Wikieditor06, ACSE, Lights, Phil- fan108, Deor, VolkovBot, Thewolf37, ABF, Parishp, Mrh30, Hersfold, Joelikesweiner, Indubitably, Vlma111, Toddles29, Maile66, Katy- didit, FergusM1970, WarddrBOT, Barneca, Sdsds, Philip Trueman, Tangz22, TXiKiBoT, DUBJAY04, BuickCenturyDriver, Dwmr, Inu- endo, Z.E.R.O., Afluent Rider, Gerrish, Finlux, Qxz, Someguy1221, Lradrama, DennyColt, Corvus cornix, MasterSci, Greatparty, JhsBot, Leafyplant, Sanfranman59, Lukezuke, Tranquility2007, Seb az86556, Pooblahsteak1234, Maxim, Quindraco, Damërung, Theperson427, Sultec, BigDunc, Pious7, Complex (de), Wearetheliving, Sarc37, Mcattell, Soulja nyn3, Pumpkin900, Sorrento11, Tzsche, Synthebot, Gorank4, Jimbob33, Enviroboy, Sai2020, Anna512, Burntsauce, FKmailliW, Gaaralover1991, Sampaultan, SchumiChamp, Watermel- onPotion, Stephen J. , Penciltime, Dmcq, AlleborgoBot, Arkore, CT Cooper, OldEmpire, Mars2035, RedRabbit1983, EmxBot, Tedstryk, Polkmn7, H92, Mikepoop, EJF, Akira112, SieBot, Biggysmalls, Zenlax, Jim77742, PlanetStar, WereSpielChequers, BotMulti- chill, Hertz1888, Arf!, Oldag07, Krawi, Gerakibot, Michaeltsantini, Mbz1, Caltas, Richardpask101, Sk8drummerd, Nickyddogg, Geiw- Teol, Kimblethestupid, Miremare, Converse rock, Arhead, Jacob102193, Arda Xi, WRK, Keilana, Grahamlandies, Mikepoo, RadicalOne, Toddst1, Meh123123, Tiptoety, Radon210, Oda Mari, Arbor to SJ, Metroidhunterx, Travis Evans, Zfaith, Gublefink, Phantasystar000, Wombatcat, Prestonmag, Mimihitam, OsamaBinLogin, Jdl108, Oxymoron83, Antonio Lopez, Nuttycoconut, RMB1987, Steven Zhang, Arkaysmith, Tombomp, AMCKen, Iain99, Murlough23, Techman224, Drsteevo, RSStockdale, BenoniBot, Emesee, Harry the Dirty Dog, Joldy, OKBot, Maelgwnbot, MadmanBot, LonelyMarble, Mygerardromance, Hamiltondaniel, Anyeverybody, Ascidian, Dabomb87, Dol- phin51, Gantuya eng, Pdxx123, C0nanPayne, Starcluster, 7macaw, Phaedrus7, Freewayguy, Athenean, MBK004, Elassint, ClueBot, LAX, Geopiet, Avenged Eightfold, Jackollie, Snigbrook, Starkiller88, T.Neo, Ndenison, Taroaldo, Arakunem, Taliska, WanderingFool, VQuakr, Tomisgooood, Regibox, FractalFusion, Dragon of the Rust, Niceguyedc, Blanchardb, सुभाष राऊत, Richerman, Iainhammer, Stepshep, Excirial, BSWright, CrazyChemGuy, GoldenGoose100, Hargitai, WikiZorro, Purlack Rave, Gtstricky, Sun Creator, Tyler, Peter.C, Jot- terbot, Imsohood, Iohannes Animosus, Ember of Light, Nvvchar, Enoch Wong, Yayyyyy, LeinSora, Jaericho, Icykenny, 石庭豐, The Red, Banime, JasonAQuest, Stepheng3, Thingg, DerBorg, MelonBot, Johnuniq, HumphreyW, NERIC-Security, DumZiBoT, XLinkBot, Boybrain656, Rror, Ost316, Edo leitner, Nepenthes, Avoided, WikHead, 68Kustom, Alexius08, Vianello, Aunt Entropy, Airplaneman, Ejosse1, RyanCross, Frog luva96, Gggh, Daffodillman, HexaChord, D.M. from Ukraine, Numerocity, Letaphsa, Slfigue, Maldek, XxAze- rothxX, Nickhalavanja, Mortense, Roentgenium111, Willking1979, AVand, Lagus970, DOI bot, LenardLenard, Element16, JJ606, Lan- don1980, Captain-tucker, Binary TSO, DougsTech, Fieldday-sunday, Mr. Wheely Guy, CanadianLinuxUser, Pitomba, Wælgæst wæfre, BenTrotsky, Mentisock, LaaknorBot, Huntyou3, Pirate Kitten, Computermonitor, Redheylin, 37ophiuchi, Nick9902, Ld100, Debresser, Soccermidgetkid, Baffle gab1978, LinkFA-Bot, Austinsunc, Sky13b, Whyicool96, Jeannie126, Cutey gk princess, Gogu10000, Mar- waja100, Setwisohi, 84user, Numbo3-bot, Tide rolls, Lightbot, Cocoamarsh, David0811, WikiDreamer Bot, Jarble, Bartledan, Hercule- Bot, Ferrariman909, Jackelfive, Yobot, EdwardLane, 2D, Amble, Becky Sayles, FregatPallada, THEN WHO WAS PHONE?, Amelio- 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 127

rationBot, CRIPP45, Lime123456789, Szajci, Synchronism, AnomieBOT, Archon 2488, Anggel95, HarryMichaelJones, IRP, Dwayne, WikipedaUsername, Neko85, Plcards1, AdjustShift, Kingpin13, Mema1221, Flewis, Materialscientist, Limideen, ImperatorExercitus, ArthurDuhurst, Rtyq2, The High Fin Sperm Whale, Citation bot, Text mdnp, Maxis ftw, ArthurBot, LilHelpa, Ands.66, Xqbot, Tinucheri- anBot II, Timir2, S h i v a (Visnu), Sionus, Iadrian yu, Capricorn42, Gigemag76, Nissanguy24, A455bcd9, Lionboy-Renae, Smk65536, DSisyphBot, Tyrol5, Mlpearc, Srich32977, Gwcoffey, Almabot, Arsia Mons, J04n, GrouchoBot, ChildofIndigo13, Rhskate, Mark Schier- becker, RibotBOT, Alan.A.Mick, Enceladusgeysers, Charvest, Doulos Christos, The Wiki Octopus, GhalyBot, Wikipedianerd413, Us441, Fotaun, Legobot III, Mooremoore, FrescoBot, NSH002, LucienBOT, Originalwana, Io Herodotus, Lookang, Lothar von Richthofen, Thayts, SiIIyLiIIyPiIIy, KokkaShinto, RoyGoldsmith, Jonathansuh, Endofskull, Bobmoney263364, Bayview101, Lahme lover, Nohars, Citation bot 1, Kobrabones, Falstaffswims, Gautier lebon, Pinethicket, AQUIMISMO, HRoestBot, Jonesey95, Tom.Reding, Pmokeefe, RedBot, Lars Washington, MastiBot, Mohehab, Lucylogan, DReifGalaxyM31, Hprmedina, Hessamnia, Fartherred, Aelfan1, IVAN3MAN, Arbero, Kgrad, FoxBot, TobeBot, Cocu, Dustynyfeathers, Vrenator, Extra999, Pbrower2a, Marcos Elias de Oliveira Júnior, Tbhotch, Ob- sidian Soul, Brakoholic, RjwilmsiBot, TjBot, Bento00, Burmiester, Mandolinface, Grondemar, DASHBot, Shabidoo, EmausBot, KurtLC, Racerx11, Primefac, GoingBatty, MartinThoma, Gwillhickers, Torturella, Muqtasidmansoor, Tommy2010, Weanisland3, Tlinnemeyer, P. S. F. Freitas, ZéroBot, CanonLawJunkie, Fæ, Maxviwe, A2soup, Nicolas Eynaud, AvicAWB, Hevron1998, H3llBot, Zap Rowsdower, Ocaasi, 3sdanog, Anglais1, L Kensington, Sailsbystars, Miyaka409, Honesty First, ChuispastonBot, Tahjanaa, Planet photometry, Mikhail Ryazanov, ClueBot NG, Macarenses, Adonis Mezzano, Ericobnn, Xession, Movses-bot, Dru of Id, Bobbyb373, AlwaysUnite, North Atlanticist Usonian, Mightymights, Helpful Pixie Bot, Newyork1501, Gob Lofa, Bibcode Bot, MKar, Gomada, SpaceChimp1992, Darouet, Badon, Davidiad, தென்காசி சுப்பிரமணியன், Dodshe, FutureTrillionaire, Cadiomals, Rgbc2000, OldSquiffyBat, Mothdust79, Brb94, Soerfm, 7903xc, Tycho Magnetic Anomaly-1, Colinmartin74, Ubiquinoid, Irockz, SoylentPurple, Justincheng12345-bot, W.D., Nick.mon, Shiltsev, Dexbot, Darekk2, Advlokanath, Blobbie244, IceOnFire97, Sidelight12, Tony Mach, Anti-Quasar, Climatophile, Reat- las, НиколаБ, Jcpag2012, Jodosma, Blackbombchu, Pwnzor.ak, Exoplanetaryscience, Astredita, Andylara2014, Crossswords, Monkbot, Filedelinkerbot, Douglas Cotton, Scarlettail, Stetson7, Tetra quark, Isambard Kingdom, Bu180 and Anonymous: 1423

7.12.2 Images

• File:15-ml-06-phobos2-A067R1.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/24/15-ml-06-phobos2-A067R1.jpg License: Public domain Contributors: http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040311a.html (Raw image at http:// marsrovers.jpl.nasa.gov/gallery/all/1/p/045/1P132176262ESF05A6P2670R8M1.HTML) Original artist: NASA/JPL/Cornell • File:391243main-MarsRover-ShelterIslandMeteorite-20091002-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/ a/a2/391243main-MarsRover-ShelterIslandMeteorite-20091002-crop.jpg License: Public domain Contributors: http://www.nasa.gov/ images/content/391243main_mer20091002-full.jpg Original artist: NASA/JPL-Caltech • File:58606main_image_feature_167_jwfull.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/88/58606main_image_ feature_167_jwfull.jpg License: Public domain Contributors: http://www.nasa.gov/mission_pages/mars/images/mer-image_feature_167. html (direct link; alt source) Original artist: NASA/JPL/Cornell • File:Adirondacksquare.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0b/Adirondacksquare.jpg License: Public do- main Contributors: Transferred from en.wikipedia Original artist: Original uploader was Sennheiser at en.wikipedia • File:Almagest-planets.svg Source: http://upload.wikimedia.org/wikipedia/commons/5/55/Almagest-planets.svg License: Public domain Contributors: Own work Original artist: Spacepotato • File:Apparent_retrograde_motion_of_Mars_in_2003.gif Source: http://upload.wikimedia.org/wikipedia/commons/7/70/Apparent_ retrograde_motion_of_Mars_in_2003.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Eugene Villar (seav) • File:Block_Island.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5f/Block_Island.jpg License: Public domain Contrib- utors: http://photojournal.jpl.nasa.gov/catalog/PIA12165 Original artist: NASA/JPL-Caltech/Cornell University • File:Comet-C2013A1-SidingSpring-NearMars-Hubble-20141019.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/ e9/Comet-C2013A1-SidingSpring-NearMars-Hubble-20141019.jpg License: Public domain Contributors: http://www.nasa.gov/sites/ default/files/comet_springs.jpg Original artist: NASA, ESA, PSI, JHU/APL, STScI/AURA • File:Comet-SidingSpring-Passing-PlanetMars-On-20141019-ArtistConcept-20140905.jpg Source: http://upload.wikimedia.org/ wikipedia/commons/d/df/Comet-SidingSpring-Passing-PlanetMars-On-20141019-ArtistConcept-20140905.jpg License: Public do- main Contributors: http://mars.jpl.nasa.gov/msl/images/Comet-Siding-Spring-Mars-Artist-Concept-full.jpg Original artist: NASA/JPL- Caltech • File:CometSidingSpring-HeadingTowardsMars-ArtistConcept-20141006.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/6/65/CometSidingSpring-HeadingTowardsMars-ArtistConcept-20141006.jpg License: Public domain Contributors: http://www.nasa.gov/sites/default/files/mars_comet-full_0.jpg Original artist: NASA • File:Commons-logo.svg Source: http://upload.wikimedia.org/wikipedia/en/4/4a/Commons-logo.svg License: ? Contributors: ? Original artist: ? • File:Conjunction_of_Jupiter_and_Moon.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c2/Conjunction_of_ Jupiter_and_Moon.jpg License: GFDL Contributors: Own work Original artist: Radoslaw Ziomber • File:Deimos-MRO.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8d/Deimos-MRO.jpg License: Public domain Con- tributors: http://marsprogram.jpl.nasa.gov/mro/gallery/press/20090309a.html Original artist: NASA/JPL-caltech/University of Arizona • File:Different_Faces_Neptune.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0d/The_four_sides_of_Neptune_ %28captured_by_the_Hubble_Space_Telescope%29.tif License: Public domain Contributors: http://hubblesite.org/newscenter/archive/ releases/2011/19/image/a/ (direct link) Original artist: NASA, ESA, and the Hubble Heritage Team (STScI/AURA) • File:Disambig_gray.svg Source: http://upload.wikimedia.org/wikipedia/en/5/5f/Disambig_gray.svg License: Cc-by-sa-3.0 Contributors: ? Original artist: ? • File:ESO_-_Uranus_(by).jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/44/ESO_-_Uranus_%28by%29.jpg License: CC BY 4.0 Contributors: Peering at Uranus's Rings as they Swing Edge-on to Earth for the First Time Since their Discovery in 1977 Original artist: ESO 128 CHAPTER 7. VENUS

• File:Earth-Moon_system_as_seen_from_Saturn_(PIA17171).jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/32/ Earth-Moon_system_as_seen_from_Saturn_%28PIA17171%29.jpg License: Public domain Contributors: http://www.nasa.gov/mission_ pages/cassini/multimedia/pia17171.html (image link) Original artist: NASA/JPL-Caltech/Space Science Institute • File:El_Capitan_sol27_pancam.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/26/El_Capitan_sol27_pancam.jpg Li- cense: Public domain Contributors: Transferred from en.wikipedia; Transfer was stated to be made by User:Pascal.Tesson. Original artist: NASA/JPL-Cornell • File:Enceladus_geysers.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0e/Enceladus_geysers.jpg License: Public do- main Contributors: http://www.jpl.nasa.gov/news/news.cfm?release=2010-061&cid=release_2010-061&msource=n20100223&tr=y& auid=5974065, http://photojournal.jpl.nasa.gov/catalog/PIA11688 Original artist: NASA/JPL/Space Science Institute • File:Europa-moon.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/54/Europa-moon.jpg License: Public domain Con- tributors: ? Original artist: ? • File:Flag_of_Europe.svg Source: http://upload.wikimedia.org/wikipedia/commons/b/b7/Flag_of_Europe.svg License: Public domain Contributors: • File based on the specification given at [1]. Original artist: User:Verdy p, User:-xfi-, User:Paddu, User:Nightstallion, User:Funakoshi, User:Jeltz, User:Dbenbenn, User:Zscout370 • File:Flag_of_Japan.svg Source: http://upload.wikimedia.org/wikipedia/en/9/9e/Flag_of_Japan.svg License: PD Contributors: ? Original artist: ? • File:Flag_of_the_Soviet_Union.svg Source: http://upload.wikimedia.org/wikipedia/commons/a/a9/Flag_of_the_Soviet_Union.svg Li- cense: Public domain Contributors: http://pravo.levonevsky.org/ Original artist: СССР • File:Flag_of_the_United_States.svg Source: http://upload.wikimedia.org/wikipedia/en/a/a4/Flag_of_the_United_States.svg License: PD Contributors: ? Original artist: ? • File:Folder_Hexagonal_Icon.svg Source: http://upload.wikimedia.org/wikipedia/en/4/48/Folder_Hexagonal_Icon.svg License: Cc-by- sa-3.0 Contributors: ? Original artist: ? • File:Great_Red_Spot_From_Voyager_1.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/ec/Great_Red_Spot_From_ Voyager_1.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00014 Original artist: NASA • File:HerschelTelescope.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/d7/HerschelTelescope.jpg License: Public do- main Contributors: Own work Original artist: Mike Young • File:Hs-2009-23-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Hs-2009-23-crop.jpg License: Public domain Contributors: Cropped from Hubblesite (STScI-2009-23) Original artist: Credit: NASA, ESA, and H. Hammel (Space Science Institute, Boulder, Colo.), and the Jupiter Impact Team • File:Hubble_sees_a_flickering_light_display_on_Saturn.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/2e/ Hubble_sees_a_flickering_light_display_on_Saturn.jpg License: ? Contributors: http://www.spacetelescope.org/images/potw1420a/ Original artist: NASA, ESA Acknowledgement: J. Nichols (University of Leicester) • File:InnerSolarSystem-en.png Source: http://upload.wikimedia.org/wikipedia/commons/f/f3/InnerSolarSystem-en.png License: Public domain Contributors: Transferred from en.wikipedia to Commons. Original artist: Mdf at English Wikipedia • File:Jupiter-bonatti.png Source: http://upload.wikimedia.org/wikipedia/commons/c/cb/Jupiter-bonatti.png License: Public domain Contributors: Guido Bonatti, De Astronomia Libri X (Basel, Nicolaus Pruknerus, 1550) Original artist: Nicolaus Pruknerus, Guido Bonatti • File:Jupiter.Aurora.HST.UV.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8e/Jupiter.Aurora.HST.UV.jpg License: Public domain Contributors: http://hubblesite.org/newscenter/archive/releases/2000/38/image/a/, http://apod.gsfc.nasa.gov/apod/ ap001219.html Original artist: John T. Clarke (University of Michigan), ESA, NASA • File:Jupiter_MAD.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/70/Jupiter_MAD.jpg License: CC BY 4.0 Contribu- tors: http://www.eso.org/public/outreach/press-rel/pr-2008/images/phot-33-08-fullres.jpg Originally uploaded 16:14, 19 November 2008 (UTC) by Lars Lindberg Christensen (talk • contribs) to en:wiki. Original artist: ESO/F. Marchis, M. Wong, E. Marchetti, P. Amico, S. Tordo • File:Jupiter_New_Horizons.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c1/Jupiter_New_Horizons.jpg License: Public domain Contributors: National Aeronautics and Space Administration Original artist: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute • File:Jupiter_and_Galilean_moons.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b0/Jupiter_and_Galilean_moons. jpg License: CC BY 2.0 Contributors: Jupiter Original artist: stewartde • File:Jupiter_by_Cassini-Huygens.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5a/Jupiter_by_Cassini-Huygens.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA02873 Original artist: NASA/JPL/University of Arizona • File:Jupiter_diagram.svg Source: http://upload.wikimedia.org/wikipedia/commons/b/b5/Jupiter_diagram.svg License: CC BY-SA 3.0 Contributors: Own work Original artist: Kelvinsong • File:Jupiter_from_Voyager_1.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c8/Jupiter_from_Voyager_1.jpg Li- cense: Public domain Contributors: http://www.jpl.nasa.gov/releases/2002/release_2002_166.html Original artist: NASA, Caltech/JPL • File:Jupiter_from_Voyager_1_PIA02855_thumbnail_300px_max_quality.ogv Source: http://upload.wikimedia.org/wikipedia/ commons/0/0e/Jupiter_from_Voyager_1_PIA02855_thumbnail_300px_max_quality.ogv License: Public domain Contributors: http://photojournal.jpl.nasa.gov/browse/PIA02855.gif linked from http://photojournal.jpl.nasa.gov/animation/PIA02855 converted to PNG images, downscaled to half size, then converted at maximum quality (10) and each frame forced to be a keyframe using programs MPlayer for Windows (version 0.6.9+SVN-r3532 using Qt 4.6.2 using MPlayer SVN r31170) and png2theora (version 1.1 binary build from 20100523) as follows: Original artist: NASA • File:Jupiter_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/2/26/Jupiter_symbol.svg License: Public domain Contributors: Own work Original artist: Lexicon 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 129

• File:Karte_Mars_Schiaparelli_MKL1888.png Source: http://upload.wikimedia.org/wikipedia/commons/d/dd/Karte_Mars_ Schiaparelli_MKL1888.png License: Public domain Contributors: Meyers Konversations-Lexikon (German encyclopaedia), 1888. Original artist: Unknown • File:Kirks_Soap_Yerkes_Mars.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5f/Kirks_Soap_Yerkes_Mars.jpg Li- cense: Public domain Contributors: Contemporary Astronomy â second edition, by Jay M. Pasachoff, published by Saunders College Publishing 1981. ISBN 0-03-057861-2 Original artist: Further attribution given within to “American Institute of Physics, Niels Library”. 1893 ad its self is attributed in text to an unnamed Chicago newspaper. • File:Lhborbits.png Source: http://upload.wikimedia.org/wikipedia/commons/0/0f/Lhborbits.png License: CC BY-SA 3.0 Contributors: Own work Original artist: en:User:AstroMark • File:Looking_saturn_in_the_eye.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/57/Looking_saturn_in_the_eye.jpg License: Public domain Contributors: http://www.nasa.gov/images/content/162349main_pia08332-516.jpg on http://www.nasa.gov/ mission_pages/cassini/multimedia/pia08332.html Original artist: NASA • File:Lowell_Mars_channels.jpg Source: http://upload.wikimedia.org/wikipedia/commons/f/f3/Lowell_Mars_channels.jpg License: Public domain Contributors: Яков Перельман - "Далёкие миры". СПб, типография Сойкина (English transliteration: Yakov Perelman - “Distant Worlds”. St. Petersburg, Soykin printing house), 1914. Original artist: Percival Lowell • File:MESSENGER_-_Venus_630_nm_stretch.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/3b/MESSENGER_-_ Venus_630_nm_stretch.jpg License: Public domain Contributors: http://messenger.jhuapl.edu/gallery/sciencePhotos/image.php?page=1& gallery_id=2&image_id=327 Original artist: NASA / JHU/APL • File:Maat_Mons_on_Venus.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/16/Maat_Mons_on_Venus.jpg License: Public domain Contributors: ? Original artist: ? • File:Mackinac_Island.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5d/Mackinac_Island.jpg License: Public domain Contributors: Transferred from ru.wikipedia; transferred to Commons by User:Bulwersator using CommonsHelper. Original artist: . Orig- inal uploader was Neck at ru.wikipedia • File:Magellan_Venus_globes.jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/a1/Magellan_Venus_globes.jpg License: Public domain Contributors: http://solarviews.com/cap/venus/venview.htm (image link) Original artist: NASA/JPL • File:Mariner_2_in_space.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/02/Mariner_2_in_space.jpg License: Pub- lic domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA04594 Original artist: NASA Jet Propulsion Laboratory (NASA-JPL)

• File:Mars-express-volcanoes-sm.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/9d/Mars-express-volcanoes-sm.jpg License: Public domain Contributors: http://marsprogram.jpl.nasa.gov/express/gallery/artwork/marsis-radarpulses.html (image link) Orig- inal artist: NASA/JPL/ Waste • File:Mars.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/1b/Mars.jpg License: Public domain Contributors: [1] [2] (im- ported from English Wikipedia) Original artist: NASA and The Hubble Heritage Team (STScI/AURA) [3] Acknowledgment: J. Bell (Cornell U.) • File:Mars.ogv Source: http://upload.wikimedia.org/wikipedia/commons/d/dd/Mars.ogv License: Public domain Contributors: Goddard Multimedia Original artist: NASA/Goddard Space Flight Center • File:MarsCuriosityRover-CoronationRock--20120817-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/f/ f8/MarsCuriosityRover-CoronationRock-N165-20120817-crop.jpg License: Public domain Contributors: http://mars.jpl.nasa.gov/msl/ images/msl_twirly20120817-660-full.jpg Original artist: NASA/JPL-Caltech/MSSS/LANL • File:MarsViking1Lander-BigJoeRock-19780211.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/1b/ MarsViking1Lander-BigJoeRock-19780211.jpg License: Public domain Contributors: Crop/Resize/JPG-Convert (using JASC Paint Shop Pro v 6.02) of file at https://en.wikipedia.org/wiki/File:Mars_Viking_11h016.png Original artist: NASA/Van der Hoorn • File:Mars_23_aug_2003_hubble.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/58/Mars_23_aug_2003_hubble.jpg License: Public domain Contributors: http://hubblesite.org/newscenter/archive/releases/2005/34/image/j/ (image link) Original artist: NASA, ESA, and The Hubble Heritage Team (STScI/AURA) • File:Mars_Earth_Comparison_2.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/93/Mars_Earth_Comparison_2.jpg License: Public domain Contributors: NASA/JPL/MSSS based on the [#Sources these sources]. Original artist: NASA/JPL/MSSS & User:DrLee • File:Mars_HST_Mollweide_map_1999.png Source: http://upload.wikimedia.org/wikipedia/commons/d/da/Mars_HST_Mollweide_ map_1999.png License: Public domain Contributors: http://hubblesite.org/gallery/album/entire_collection/pr1999027f/ (Original Tif, re- saved as PNG].) Original artist: NASA. • File:Mars_Hubble.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/76/Mars_Hubble.jpg License: Public domain Con- tributors: http://hubblesite.org/newscenter/archive/releases/2001/24/image/a/ (direct link) Original artist: NASA and The Hubble Heritage Team (STScI/AURA) • File:Mars_Viking_11d128.png Source: http://upload.wikimedia.org/wikipedia/commons/1/1b/Mars_Viking_11d128.png License: Pub- lic domain Contributors: Own work based on images in the NASA Viking image archive Original artist: “Roel van der Hoorn (Van der Hoorn)" • File:Mars_atmosphere_2.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/cd/Mars_atmosphere_2.jpg License: Public domain Contributors: http://solarsystem.nasa.gov/multimedia/gallery/Mars__atmosphere.jpg Original artist: NASA • File:Mars_oppositions_2003-2018.png Source: http://upload.wikimedia.org/wikipedia/commons/4/48/Mars_oppositions_2003-2018. png License: Public domain Contributors: Own work Original artist: self • File:Mars_rock_Mimi_by_Spirit_rover.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/28/Mars_rock_Mimi_by_ Spirit_rover.jpg License: Public domain Contributors: http://mars.nasa.gov/mer/gallery/press/spirit/20040213a.html (image link) Origi- nal artist: NASA/JPL/Cornell 130 CHAPTER 7. VENUS

• File:Mars_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/b/b7/Mars_symbol.svg License: Public domain Contrib- utors: Own work Original artist: This vector image was created with Inkscape by Lexicon, and then manually replaced by sarang. • File:Mars_topography_(MOLA_dataset)_with_poles_HiRes.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/2c/ Mars_topography_%28MOLA_dataset%29_with_poles_HiRes.jpg License: Public domain Contributors: http://mola.gsfc.nasa.gov/ images.html and http://photojournal.jpl.nasa.gov/catalog/PIA02993 Original artist: NASA / JPL / USGS • File:Marsorbitsolarsystem.gif Source: http://upload.wikimedia.org/wikipedia/commons/5/54/Marsorbitsolarsystem.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java Simulation = Francisco Esquembre • File:Martian_atmosphere_photographed_by_Mars_Orbiter_Mission_Spacecraft.jpg Source: http://upload.wikimedia.org/ wikipedia/en/7/78/Martian_atmosphere_photographed_by_Mars_Orbiter_Mission_Spacecraft.jpg License: Public domain Contributors: Check out @MarsOrbiter's Tweet: https://twitter.com/MarsOrbiter/status/515132968939954177?s=09 Original artist: Indian Space and Research Organisation • File:Martian_north_polar_cap.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/62/Martian_north_polar_cap.jpg Li- cense: Public domain Contributors: http://www.msss.com/mars_images/moc/may_2000/n_pole/ file Original artist: NASA/JPL/Malin Space Science Systems • File:Mgn_p39146.png Source: http://upload.wikimedia.org/wikipedia/commons/b/bb/Mgn_p39146.png License: Public domain Contrib- utors: ? Original artist: ? • File:Msl20110526_MSL_Artist_Concept_PIA14164-full.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/27/ Msl20110526_MSL_Artist_Concept_PIA14164-full.jpg License: Public domain Contributors: http://marsprogram.jpl.nasa.gov/msl/ multimedia/images/?ImageID=3511 Original artist: NASA • File:NASA-14090-Comet-C2013A1-SidingSpring-Hubble-20140311.jpg Source: http://upload.wikimedia.org/wikipedia/commons/ a/ac/NASA-14090-Comet-C2013A1-SidingSpring-Hubble-20140311.jpg License: Public domain Contributors: http://www.nasa.gov/ sites/default/files/14-090-hubble-comet_0.jpg Original artist: NASA, ESA, and J.-Y. Li (Planetary Science Institute) • File:NASA-Cassini-Saturn-TitanFlybyTests-20140617.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/3a/ NASA-Cassini-Saturn-TitanFlybyTests-20140617.jpg License: Public domain Contributors: http://www.jpl.nasa.gov/images/cassini/ 20140617/cassini20140617-full.jpg Original artist: NASA/JPL-Caltech • File:NASA-MarsRock-Yogi-SuperRes.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c4/ NASA-MarsRock-Yogi-SuperRes.jpg License: Public domain Contributors: http://mars.jpl.nasa.gov/MPF/ops/Yogi_super_res.jpg Original artist: NASA/JPL/Dr. Timothy Parker • File:NASA14135-Jupiter-GreatRedSpot-Shrinks-20140515.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/30/ NASA14135-Jupiter-GreatRedSpot-Shrinks-20140515.jpg License: Public domain Contributors: http://www.nasa.gov/sites/default/ files/14-135-jupiter2_0.jpg Original artist: NASA, ESA, and A. Simon (Goddard Space Flight Center) • File:NASA_Curiosity_rover_-_Link_to_a_Watery_Past_(692149main_Williams-2pia16188-43).jpg Source: http: //upload.wikimedia.org/wikipedia/commons/7/79/NASA_Curiosity_rover_-_Link_to_a_Watery_Past_%28692149main_ Williams-2pia16188-43%29.jpg License: Public domain Contributors: Link to a Watery Past Original artist: NASA/JPL-Caltech/MSSS • File:Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/ Nasa_mars_opportunity_rock_water_150_eng_02mar04.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/ catalog/pia05474 Original artist: NASA/JPL/US • File:Neptune'{}s_Great_Dark_Spot.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/df/Neptune%27s_Great_Dark_ Spot.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00052 Original artist: NASA / Jet Propulsion Lab • File:Neptune,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/d5/Neptune%2C_Earth_size_ comparison.jpg License: Public domain Contributors: This image was made from NASA Earth America 2010.jpg and Neptune Full.jpg Original artist: ? • File:Neptune-Methane.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/6a/Neptune-Methane.jpg License: Public do- main Contributors: frame from video on Hubblesite: STScI-2005-22 Original artist: Hubble Space Telescope • File:Neptune-visible.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/63/Neptune-visible.jpg License: Public domain Contributors: ? Original artist: ? • File:Neptune_Full.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/56/Neptune_Full.jpg License: Public domain Con- tributors: JPL image Original artist: NASA • File:Neptune_Orbit.gif Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Neptune_Orbit.gif License: CC BY-SA 3.0 Con- tributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java Simulation = Francisco Esquembre • File:Neptune_clouds.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c8/Neptune_clouds.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00058 Original artist: NASA / Jet Propulsion Lab • File:Neptune_diagram.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/fd/Neptune_diagram.svg License: CC BY-SA 3.0 Contributors: http://solarsystem.nasa.gov/multimedia/gallery/Neptune_Int-browse.jpg, which is in the public domain Original artist: NASA; Pbroks13 (redraw) • File:Neptune_storms.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8c/Neptune_storms.jpg License: Public domain Contributors: http://antwrp.gsfc.nasa.gov/apod/ap010821.html Original artist: NASA/Voyager 2 Team • File:Neptune_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Neptune_symbol.svg License: Public domain Contributors: Own work Original artist: Amit6 • File:Neptunerings.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/87/Neptunerings.jpg License: Public domain Contrib- utors: Transferred from en.wikipedia; transfer was stated to be made by User:Cocu. Original artist: Original uploader was Serendipodous at en.wikipedia 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 131

• File:Office-book.svg Source: http://upload.wikimedia.org/wikipedia/commons/a/a8/Office-book.svg License: Public domain Contribu- tors: This and myself. Original artist: Chris Down/Tango project • File:Olympus_Mons_alt.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/00/Olympus_Mons_alt.jpg License: Public do- main Contributors: Edited version of File:Olympus Mons.jpg originally from http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars. html#features. Original artist: Image by NASA, modifications by Seddon • File:Orbits_of_Phobos_and_Deimos.gif Source: http://upload.wikimedia.org/wikipedia/commons/d/db/Orbits_of_Phobos_and_ Deimos.gif License: CC BY-SA 2.5 Contributors: ? Original artist: ? • File:P11saturnb.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c7/P11saturnb.jpg License: Public domain Contributors: ? Original artist: ? • File:PIA00819left-MarsRock-BarnacleBill.gif Source: http://upload.wikimedia.org/wikipedia/commons/2/2f/ PIA00819left-MarsRock-BarnacleBill.gif License: Public domain Contributors: http://photojournal.jpl.nasa.gov/figures/PIA00819left.gif Original artist: NASA/JPL • File:PIA01482_Saturn_Montage.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/7d/PIA01482_Saturn_Montage.jpg License: Public domain Contributors: JPL image PIA01482 Original artist: NASA • File:PIA01627_Ringe.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/PIA01627_Ringe.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA01627 Original artist: NASA/JPL/Cornell University • File:PIA02863_-_Jupiter_surface_motion_animation_thumbnail_300px_10fps.ogv Source: http://upload.wikimedia.org/ wikipedia/commons/6/68/PIA02863_-_Jupiter_surface_motion_animation_thumbnail_300px_10fps.ogv License: Public domain Contributors: http://photojournal.jpl.nasa.gov/archive/PIA02863.gif linked from http://photojournal.jpl.nasa.gov/animation/PIA02863, transcoded and downscaled to a maximum quality (10) Theora video, each frame forced to be a keyframe, using programs MPlayer for Windows (version 0.6.9+SVN-r3532 using Qt 4.6.2 using MPlayer SVN r31170) and png2theora (version 1.1 binary build from 20100523) as follows: Original artist: NASA/JPL/University of Arizona • File:PIA02879_-_A_New_Year_for_Jupiter_and_Io.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/65/PIA02879_ -_A_New_Year_for_Jupiter_and_Io.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA02879 Orig- inal artist: NASA/JPL/University of Arizona • File:PIA05482_modest.jpg Source: http://upload.wikimedia.org/wikipedia/commons/f/fe/PIA05482_modest.jpg License: Public do- main Contributors: http://photojournal.jpl.nasa.gov/catalog/pia05482 Original artist: NASA/JPL/Cornell • File:PIA07269-Mars_Rover_Opportunity-Iron_Meteorite.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/62/ PIA07269-Mars_Rover_Opportunity-Iron_Meteorite.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/ PIA07269 (TIFF converted into 100% quality JPEG) Original artist: NASA/JPL/Cornell • File:PIA09089-RA3--closeup_annotated.png Source: http://upload.wikimedia.org/wikipedia/en/d/d3/ PIA09089-RA3-hirise-closeup_annotated.png License: PD Contributors: ? Original artist: ? • File:PIA13418_-_Oileán_Ruaidh_meteorite_on_Mars_(false_colour).jpg Source: http://upload.wikimedia.org/wikipedia/ commons/a/a9/PIA13418_-_Oile%C3%A1n_Ruaidh_meteorite_on_Mars_%28false_colour%29.jpg License: Public domain Contribu- tors: NASA and JPL Original artist: NASA/JPL-Caltech/Cornell University • File:PIA14762-MarsCuriosityRover-BathurstInletRock.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/15/ PIA14762-MarsCuriosityRover-BathurstInletRock.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/ PIA14762.jpg Original artist: NASA/JPL-Caltech/Malin Space Science Systems • File:PIA15038_-_Spirit_lander_and_Bonneville_Crater_on_Mars.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/ 1c/PIA15038_-_Spirit_lander_and_Bonneville_Crater_on_Mars.jpg License: Public domain Contributors: http://photojournal.jpl.nasa. gov/catalog/PIA15038 Original artist: NASA/JPL-Caltech/Univ. of Arizona • File:PIA16068_-_Mars_Curiosity_Rover_-_Aeolis_Mons_-_20120817.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/b/bb/PIA16068_-_Mars_Curiosity_Rover_-_Aeolis_Mons_-_20120817.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16068.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA16187-MarsCuriosityRover-GoulburnRock-20120817-crop.jpg Source: http://upload.wikimedia.org/wikipedia/commons/ d/d5/PIA16187-MarsCuriosityRover-GoulburnRock-20120817-crop.jpg License: Public domain Contributors: http://www.nasa.gov/ sites/default/files/images/692138main_malin-4pia16187-43_full.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA16192-MarsCuriosityRover-Target-JakeRock-20120927.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/ 3a/PIA16192-MarsCuriosityRover-Target-JakeRock-20120927.jpg License: Public domain Contributors: http://photojournal.jpl.nasa. gov/catalog/PIA16192 (direct link) Original artist: NASA/JPL-Caltech/MSSS • File:PIA16239_High-Resolution_Self-Portrait_by_Curiosity_Rover_Arm_Camera.jpg Source: http://upload.wikimedia.org/ wikipedia/commons/d/dc/PIA16239_High-Resolution_Self-Portrait_by_Curiosity_Rover_Arm_Camera.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA16239 Original artist: • Derivative work including grading, distortion correction, minor local adjustments and rendering from tiff-file: Julian Herzog • File:PIA16450-MarsDustStorm-20121118.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b2/ PIA16450-MarsDustStorm-20121118.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16450.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA16452-MarsCuriosityRover-Rocknest3Rock-20121005.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b1/ PIA16452-MarsCuriosityRover-Rocknest3Rock-20121005.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/ jpeg/PIA16452.jpg Original artist: NASA/JPL-Caltech/Malin Space Science Systems • File:PIA16454-MarsDustStorm-20121125.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/9c/ PIA16454-MarsDustStorm-20121125.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16454.jpg Original artist: NASA/JPL-Caltech/MSSS 132 CHAPTER 7. VENUS

• File:PIA16791-MarsCuriosityRover-Composition-YellowknifeBayRocks.png Source: http://upload.wikimedia.org/wikipedia/ commons/7/71/PIA16791-MarsCuriosityRover-Composition-YellowknifeBayRocks.png License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA16791 Original artist: NASA/JPL-Caltech/University of Guelph • File:PIA16795-MarsCuriosityRover-TintinaRock-Context-20130119.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/3/32/PIA16795-MarsCuriosityRover-TintinaRock-Context-20130119.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA16795.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA17062-MarsCuriosityRover-HottahRockOutcrop-20120915.jpg Source: http://upload.wikimedia.org/wikipedia/commons/ 0/00/PIA17062-MarsCuriosityRover-HottahRockOutcrop-20120915.jpg License: Public domain Contributors: http://photojournal.jpl. nasa.gov/jpeg/PIA17062.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA17074-MarsOpportunityRover-EsperanceRock-20130223-fig1.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/2/2d/PIA17074-MarsOpportunityRover-EsperanceRock-20130223-fig1.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA17074 (image link) Original artist: NASA/JPL-Caltech/Cornell Univ./Arizona State Univ. • File:PIA18078-PossibleBeginning-NewMoonOfPlanetSaturn-20130415.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/a/a0/PIA18078-PossibleBeginning-NewMoonOfPlanetSaturn-20130415.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA18078.jpg Original artist: NASA/JPL-Caltech/Space Science Institute • File:PIA18274-Saturn-NorthPolarHexagon-Cassini-20140402.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/8e/ PIA18274-Saturn-NorthPolarHexagon-Cassini-20140402.jpg License: Public domain Contributors: http://www.nasa.gov/sites/default/ files/pia18274_full.jpg Original artist: NASA/JPL-Caltech/Space Science Institute • File:PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg Source: http://upload.wikimedia.org/ wikipedia/commons/e/e8/PIA18381-Mars-FreshAsteroidImpact2012-Before27March-After28March.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/jpeg/PIA18381.jpg Original artist: NASA/JPL-Caltech/MSSS • File:PIA18611-Mars-CometSidingSpringFlyby-20141009.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/12/ PIA18611-Mars-CometSidingSpringFlyby-20141009.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/figures/ PIA18611_fig1.jpg Original artist: NASA/JPL-Caltech • File:PIA18613-MarsMAVEN-Atmosphere-3UV-Views-20141014.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/ 00/PIA18613-MarsMAVEN-Atmosphere-3UV-Views-20141014.jpg License: Public domain Contributors: http://photojournal.jpl.nasa. gov/jpeg/PIA18613.jpg Original artist: NASA/Univ. of Colorado • File:PIA19088-MarsCuriosityRover-MethaneSource-20141216.png Source: http://upload.wikimedia.org/wikipedia/commons/6/69/ PIA19088-MarsCuriosityRover-MethaneSource-20141216.png License: Public domain Contributors: http://mars.jpl.nasa.gov/msl/ images/methane-source-mars-rover-curiosity-pia19088-full.jpg Original artist: NASA/JPL-Caltech • File:People_icon.svg Source: http://upload.wikimedia.org/wikipedia/commons/3/37/People_icon.svg License: CC0 Contributors: Open- Clipart Original artist: OpenClipart • File:Phases-of-Venus.svg Source: http://upload.wikimedia.org/wikipedia/commons/d/d1/Phases-of-Venus.svg License: Public domain Contributors: Based on PD raster image Image:Phasesofvenus.jpg, http://history.nasa.gov/SP-424/p4.jpg Original artist: Nichalp 09:56, 11 June 2006 (UTC) • File:Phases_Venus.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/11/Phases_Venus.jpg License: Attribution Contribu- tors: Transferred from fr.wikipedia; transfer was stated to be made by User:Mu301. Original artist: Statis Kalyvas - VT-2004 programme (Original uploader was Sting at fr.wikipedia) • File:Phobos_colour_2008.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5c/Phobos_colour_2008.jpg License: Public domain Contributors: NASA/JPL-Caltech/University of Arizona Original artist: NASA/JPL-Caltech/University of Arizona • File:Pioneer_Venus_2_inspection.jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/4c/Pioneer_Venus_2_inspection. jpg License: Public domain Contributors: http://nix.larc.nasa.gov/info;jsessionid=6v6flfypvl37?id=AC77-0376-8&orgid=9 Original artist: NASA Ames Research Center (NASA-ARC) • File:Pioneer_Venus_orbiter.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/98/Pioneer_Venus_orbiter.jpg License: Public domain Contributors: ? Original artist: ? • File:Portal-puzzle.svg Source: http://upload.wikimedia.org/wikipedia/en/f/fd/Portal-puzzle.svg License: Public domain Contributors: ? Original artist: ? • File:Portrait_of_Jupiter_from_Cassini.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/75/Portrait_of_Jupiter_ from_Cassini.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA04866 Original artist: NASA/JPL/Space Science Institute • File:Pot_of_gold_upclose.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/81/Pot_of_gold_upclose.jpg License: Public domain Contributors: Transferred from en.wikipedia; transferred to Commons by User:Mike Peel using CommonsHelper. Primary source: http://mars.nasa.gov/mer/gallery/press/spirit/20040615a.html Original artist: NASA. Original uploader was Stanthejeep at en.wikipedia • File:Proteus_(Voyager_2).jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/83/Proteus_%28Voyager_2%29.jpg Li- cense: Public domain Contributors: 1989N1 Surface Detail (PIA00062) Original artist: Voyager 2, NASA • File:Retrogadation1.png Source: http://upload.wikimedia.org/wikipedia/commons/e/e7/Retrogadation1.png License: Public domain Contributors: self by W!B: (using StarOffice Draw) Original artist: W!B: • File:Rotatingsaturnhexagon.gif Source: http://upload.wikimedia.org/wikipedia/commons/b/bd/Rotatingsaturnhexagon.gif License: Public domain Contributors: • http://photojournal.jpl.nasa.gov/catalog/PIA09187 Original artist: NASA • File:Saturn'{}s_A_Ring_From_the_Inside_Out.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0d/Saturn%27s_A_ Ring_From_the_Inside_Out.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA05075 Original artist: NASA/JPL/University of Colorado 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 133

• File:Saturn'{}s_double_aurorae_(captured_by_the_Hubble_Space_Telescope).jpg Source: http://upload.wikimedia.org/wikipedia/ commons/b/b1/Saturn%27s_double_aurorae_%28captured_by_the_Hubble_Space_Telescope%29.jpg License: Public domain Contribu- tors: http://hubblesite.org/newscenter/archive/releases/2010/09/image/a/ (direct link) Original artist: NASA, ESA, and Jonathan Nichols (University of Leicester) • File:Saturn,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/39/Saturn%2C_Earth_size_ comparison.jpg License: Public domain Contributors: ? Original artist: The original uploader was Brian0918 at English Wikipedia

• File:Saturn-27-03-04.jpeg Source: http://upload.wikimedia.org/wikipedia/commons/c/c0/Saturn-27-03-04.jpeg License: Attribution Contributors: Homepage of Rochus Hess Original artist: Rochus Hess • File:Saturn-bonatti.PNG Source: http://upload.wikimedia.org/wikipedia/commons/8/8a/Saturn-bonatti.PNG License: Public domain Contributors: Guido Bonatti, De Astronomia Libri X (Basel, Nicolaus Pruknerus, 1550) Original artist: Nicolaus Pruknerus, Guido Bonatti • File:Saturn.ogg Source: http://upload.wikimedia.org/wikipedia/commons/c/c6/Saturn.ogg License: CC BY-SA 3.0 Contributors: • Derivative of Saturn Original artist: Speaker: Mangst Authors of the article • File:Saturn_Equinox_09212014.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/d6/Saturn_Equinox_09212014.jpg Li- cense: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA11667 Original artist: NASA/JPL/Space Science Institute • File:Saturn_Robert_Hooke_1666.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/27/Saturn_Robert_Hooke_1666.jpg License: Public domain Contributors: Philosophical Transactions (Royal Society publication) Original artist: Robert Hooke • File:Saturn_Storm.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/29/Saturn_Storm.jpg License: Public domain Con- tributors: http://www.jpl.nasa.gov/news/news.cfm?release=2011-203 Original artist: NASA/JPL-Caltech/SSI • File:Saturn_diagram.svg Source: http://upload.wikimedia.org/wikipedia/commons/2/2d/Saturn_diagram.svg License: CC BY-SA 3.0 Contributors: Own work Original artist: Kelvinsong • File:Saturn_eclipse.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/ba/Saturn_eclipse.jpg License: Public domain Con- tributors: http://photojournal.jpl.nasa.gov/catalog/PIA08329 (compressed version of http://photojournal.jpl.nasa.gov/tiff/PIA08329.tif) Original artist: NASA/JPL/Space Science Institute • File:Saturn_from_Cassini_Orbiter_(2007-01-19).jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Saturn_from_ Cassini_Orbiter_%282007-01-19%29.jpg License: Public domain Contributors: ? Original artist: ? • File:Saturn_in_natural_colors_(captured_by_the_Hubble_Space_Telescope).jpg Source: http://upload.wikimedia.org/wikipedia/ commons/d/d4/Saturn_in_natural_colors_%28captured_by_the_Hubble_Space_Telescope%29.jpg License: Public domain Contributors: http://www.spacetelescope.org/images/html/opo9828c.html (direct link) Original artist: Hubble Heritage Team (AURA/STScI/NASA/ESA) • File:Saturn_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/7/74/Saturn_symbol.svg License: Public domain Con- tributors: Own work Original artist: Lexicon • File:Saturnoppositions.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/c6/Saturnoppositions.jpg License: CC-BY-SA- 3.0 Contributors: ? Original artist: ? • File:Sol454_Marte_spirit.jpg Source: http://upload.wikimedia.org/wikipedia/commons/4/41/Sol454_Marte_spirit.jpg License: Public domain Contributors: http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20050420a.html Original artist: NASA/JPL • File:SolarSystem_OrdersOfMagnitude_Sun-Jupiter-Earth-Moon.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/ 02/SolarSystem_OrdersOfMagnitude_Sun-Jupiter-Earth-Moon.jpg License: CC BY-SA 3.0 Contributors: • File:The Sun by the Atmospheric Imaging Assembly of NASA's Solar Dynamics Observatory - 20100819.jpg Original artist: Tdadamemd • File:Solar_system.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/83/Solar_system.jpg License: Public domain Contrib- utors: ? Original artist: ? • File:Solarsystem3DJupiter.gif Source: http://upload.wikimedia.org/wikipedia/commons/0/08/Solarsystem3DJupiter.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java Simulation = Francisco Esquembre • File:Sound-icon.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/47/Sound-icon.svg License: LGPL Contributors: Derivative work from Silsor's versio Original artist: Crystal SVG icon set • File:South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/c/cb/South_Polar_Cap_of_Mars_during_Martian_South_summer_2000.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA02393 http://www.msss.com/mars_images/moc/4_27_00_spcap/ file Original artist: NASA/JPL/MSSS • File:Speakerlink-new.svg Source: http://upload.wikimedia.org/wikipedia/commons/3/3b/Speakerlink-new.svg License: CC0 Contribu- tors: Own work Original artist: Kelvinsong • File:Spirit_Mars_Silica_April_20_2007.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/dd/Spirit_Mars_Silica_ April_20_2007.jpg License: Public domain Contributors: ? Original artist: ? • File:Symbol_book_class2.svg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Symbol_book_class2.svg License: CC BY-SA 2.5 Contributors: Mad by Lokal_Profil by combining: Original artist: Lokal_Profil • File:Synthetic_Venus_atmosphere_absorption_spectrum.gif Source: http://upload.wikimedia.org/wikipedia/commons/3/34/ Synthetic_Venus_atmosphere_absorption_spectrum.gif License: CC BY-SA 3.0 Contributors: Own work using: Hitran on the Web Information System http://hitran.iao.ru/ (Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge, MA, USA and V.E. Zuev Insitute of Atmosperic Optics (IAO), Tomsk, Russia). Original artist: Darekk2 using Hitran on the Web Information System 134 CHAPTER 7. VENUS

• File:Synthetic_atmosphere_absorption_spectrum.gif Source: http://upload.wikimedia.org/wikipedia/commons/6/61/Synthetic_ atmosphere_absorption_spectrum.gif License: CC BY-SA 3.0 Contributors: Own work using: Hitran on the Web Information System. http://hitran.iao.ru/ (Harvard-Smithsonian Center for Astrophysics (CFA), Cambridge, MA, USA, V.E. Zuev Insitute of Atmosperic Optics (IAO), Tomsk, Russia). Original artist: Darekk2 using Hitran on the Web Information System • File:TerraformedVenus.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/b9/TerraformedVenus.jpg License: CC-BY- SA-3.0 Contributors: Transferred from en.wikipedia to Commons. Original artist: Ittiz at English Wikipedia • File:Terrestrial_Planets_Size_Comp_True_Color.png Source: http://upload.wikimedia.org/wikipedia/commons/a/a7/Terrestrial_ Planets_Size_Comp_True_Color.png License: Public domain Contributors: Own work, based on the [#Sources these sources]. Original artist: Scooter20 • File:Tharsis_-_Valles_Marineris_MOLA_shaded_colorized_zoom_32.jpg Source: http://upload.wikimedia.org/wikipedia/ commons/2/22/Tharsis_-_Valles_Marineris_MOLA_shaded_colorized_zoom_32.jpg License: Public domain Contributors: JMARS Original artist: NASA / JPL-Caltech / • File:TheKuiperBelt_classes-en.svg Source: http://upload.wikimedia.org/wikipedia/commons/e/ed/TheKuiperBelt_classes-en.svg Li- cense: CC-BY-SA-3.0 Contributors: Image:TheKuiperBelt classes.PNG from wikimedia commons, uploaded by Eurocommuter; license : GFDL + cc-by-sa-2.5,2.0,1.0 Original artist: Lilyu and Eurocommuter • File:The_Galilean_satellites_(the_four_largest_moons_of_Jupiter).tif Source: http://upload.wikimedia.org/wikipedia/commons/a/ af/The_Galilean_satellites_%28the_four_largest_moons_of_Jupiter%29.tif License: Public domain Contributors: http://photojournal.jpl. nasa.gov/catalog/PIA01299 (direct link) Original artist: NASA/JPL/DLR • File:Top_of_Atmosphere.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/be/Top_of_Atmosphere.jpg License: Public domain Contributors: http://eol.jsc.nasa.gov/scripts/sseop/photo.pl?mission=ISS013&roll=E&frame=54329 Original artist: NASA Earth Observatory • File:Triton_moon_mosaic_Voyager_2_(large).jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/a6/Triton_moon_ mosaic_Voyager_2_%28large%29.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00317 Original artist: NASA / Jet Propulsion Lab / U.S. Geological Survey • File:USGS-MarsMap-sim3292-20140714-crop.png Source: http://upload.wikimedia.org/wikipedia/commons/1/1f/ USGS-MarsMap-sim3292-20140714-crop.png License: Public domain Contributors: http://pubs.usgs.gov/sim/3292/pdf/sim3292_ map.pdf Original artist: USGS • File:Uranian_Magnetic_field.gif Source: http://upload.wikimedia.org/wikipedia/commons/a/a8/Uranian_Magnetic_field.gif License: Public domain Contributors: ? Original artist: ? • File:Uranian_moon_montage.jpg Source: http://upload.wikimedia.org/wikipedia/commons/6/6f/Uranian_moon_montage.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA01361 http://ciclops.org/view/3461/Uranus_-_Montage_of_Uranus_five_largest_satellites Original artist: NASA/JPL • File:Uranus'{}s_astrological_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/9/94/Uranus%27s_astrological_ symbol.svg License: Public domain Contributors: Own work Original artist: Lexicon • File:Uranus,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/2/2a/Uranus%2C_Earth_size_ comparison.jpg License: Public domain Contributors: This image was made from NASA Earth America 2010.jpg and Uranus2.jpg (colour adjustment) or Uranus (Edited).jpg Original artist: (old version user: Brian0918) • File:Uranus-intern-en.png Source: http://upload.wikimedia.org/wikipedia/commons/f/fe/Uranus-intern-en.png License: Public domain Contributors: • Uranus-intern-de.png Original artist: Uranus-intern-de.png: FrancescoA • File:Uranus2.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/3d/Uranus2.jpg License: Public domain Contrib- utors: http://web.archive.org/web/20090119235457/http://planetquest.jpl.nasa.gov/milestones_show/slide1.html Original artist: NASA/JPL/Voyager mission • File:Uranus_Dark_spot.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/52/Uranus_Dark_spot.jpg License: Public do- main Contributors: Transferred from en.wikipedia; transferred to Commons by User:Shizhao using CommonsHelper. Original artist: Orig- inal uploader was Ruslik0 at en.wikipedia • File:Uranus_Final_Image.jpg Source: http://upload.wikimedia.org/wikipedia/commons/a/af/Uranus_Final_Image.jpg License: Public domain Contributors: http://photojournal.jpl.nasa.gov/catalog/PIA00143 Original artist: NASA • File:Uranus_Orbit.gif Source: http://upload.wikimedia.org/wikipedia/commons/7/76/Uranus_Orbit.gif License: CC BY-SA 3.0 Con- tributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java Simulation = Francisco Esquembre • File:Uranus_clouds.jpg Source: http://upload.wikimedia.org/wikipedia/commons/0/0e/Uranus_clouds.jpg License: Public domain Con- tributors: http://hubblesite.org/newscenter/archive/releases/2007/32/image/c/ Original artist: NASA, ESA, and M. Showalter (SETI Insti- tute) • File:Uranus_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/f1/Uranus_symbol.svg License: Public domain Contributors: Own work Original artist: Lexicon • File:Uranusandrings.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/e4/Uranusandrings.jpg License: Public domain Contributors: http://www.astronomy.com/asy/default.aspx?c=a&id=1226 : from http://hubblesite.org/newscenter/archive/releases/2002/ 28/image/k/ or http://hubblesite.org/newscenter/archive/releases/1998/35/image/a/ Original artist: Hubble Space Telescope - NASA Mar- shall Space Flight Center • File:Uranuscolour.png Source: http://upload.wikimedia.org/wikipedia/commons/f/fa/Uranuscolour.png License: Public domain Con- tributors: ? Original artist: ? • File:Urbain_Le_Verrier.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/89/Urbain_Le_Verrier.jpg License: Public do- main Contributors: Originally from en.wikipedia; description page is (was) here Original artist: User Magnus Manske on en.wikipedia 7.12. TEXT AND IMAGE SOURCES, CONTRIBUTORS, AND LICENSES 135

• File:Venera9.png Source: http://upload.wikimedia.org/wikipedia/en/1/15/Venera9.png License: ? Contributors: http://www.mentallandscape.com/C_CatalogVenus.htm Original artist: Soviet Union//Venera 9 • File:Venus,_Earth_size_comparison.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/92/Venus%2C_Earth_size_ comparison.jpg License: Public domain Contributors: The Earth seen from .jpg Venus globe.jpg Original artist: NASA Venus image: NASA / JPL (from Magellan) • File:Venus-pacific-levelled.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/52/Venus-pacific-levelled.jpg License: CC BY-SA 3.0 Contributors: http://en.wikipedia.org/wiki/Image:Venus_with_reflection.jpg Original artist: Brocken Inaglory • File:Venus-real.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/51/Venus-real.jpg License: ? Contributors: http:// astrosurf.com/nunes/explor/explor_m10.htm Original artist: NASA/Ricardo Nunes • File:Venus-real_color.jpg Source: http://upload.wikimedia.org/wikipedia/commons/e/e5/Venus-real_color.jpg License: ? Contributors: http://www.astrosurf.com/nunes/explor/explor_m10.htm Original artist: NASA or Ricardo Nunes • File:Venus2_mag_big.png Source: http://upload.wikimedia.org/wikipedia/commons/4/48/Venus2_mag_big.png License: Public domain Contributors: Image from NASA website, and converted to PNG format Original artist: Magellan Team, JPL, NASA. • File:VenusLanderTopo.jpg Source: http://upload.wikimedia.org/wikipedia/commons/9/98/VenusLanderTopo.jpg License: CC BY-SA 3.0 Contributors: • Pioneer Original artist: Zamonin • File:Venus_Drawing.jpg Source: http://upload.wikimedia.org/wikipedia/commons/7/73/Venus_Drawing.jpg License: Public domain Contributors: Philosophical Transactions of the Royal Society Original artist: Captain James Cook and Charles Green • File:Venus_Rover.jpg Source: http://upload.wikimedia.org/wikipedia/commons/1/15/Venus_Rover.jpg License: Public domain Contrib- utors: ? Original artist: ? • File:Venus_airplane.JPG Source: http://upload.wikimedia.org/wikipedia/en/f/f7/Venus_airplane.JPG License: PD Contributors: ? Orig- inal artist: ? • File:Venus_globe.jpg Source: http://upload.wikimedia.org/wikipedia/commons/8/85/Venus_globe.jpg License: Public domain Contrib- utors: http://photojournal.jpl.nasa.gov/catalog/PIA00104 Original artist: NASA • File:Venus_structure.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/cc/Venus_structure.jpg License: CC-BY-SA-3.0 Contributors: ? Original artist: ? • File:Venus_symbol.svg Source: http://upload.wikimedia.org/wikipedia/commons/6/66/Venus_symbol.svg License: Public domain Con- tributors: Own work Unicode U+2640 (♀). Original artist: Kyle the hacker • File:Venusorbitsolarsystem.gif Source: http://upload.wikimedia.org/wikipedia/commons/b/b7/Venusorbitsolarsystem.gif License: CC BY-SA 3.0 Contributors: Own work Original artist: Lookang many thanks to author of original simulation = Todd K. Timberlake author of Easy Java Simulation = Francisco Esquembre • File:Venuspioneeruv.jpg Source: http://upload.wikimedia.org/wikipedia/commons/b/bc/Venuspioneeruv.jpg License: Public domain Contributors: NSSDC Photo Gallery Venus direct link to the big TIFF Version:ftp://nssdcftp.gsfc.nasa.gov/photo_gallery/hi-res/planetary/ venus/pvo_uv_790226.tiff Original artist: NASA • File:Venustransit_2004-06-08_07-49.jpg Source: http://upload.wikimedia.org/wikipedia/commons/d/db/Venustransit_2004-06-08_ 07-49.jpg License: CC-BY-SA-3.0 Contributors: photo taken by Jan Herold (German Wikipedian) Original artist: de:Benutzer:Klingon • File:Vénus_télescope.jpg Source: http://upload.wikimedia.org/wikipedia/commons/c/cc/V%C3%A9nus_t%C3%A9lescope.jpg Li- cense: GFDL Contributors: http://astrosurf.com/lecleire/2007/venuscolor_100907_05h22.jpg Original artist: Marc Lecleire • File:War-of-the-worlds-tripod.jpg Source: http://upload.wikimedia.org/wikipedia/commons/5/5a/War-of-the-worlds-tripod.jpg Li- cense: Public domain Contributors: ? Original artist: Henrique Alvim Correa • File:Wikibooks-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/fa/Wikibooks-logo.svg License: CC BY-SA 3.0 Contributors: Own work Original artist: User:Bastique, User:Ramac et al. • File:Wikinews-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/2/24/Wikinews-logo.svg License: CC BY-SA 3.0 Contributors: This is a cropped version of Image:Wikinews-logo-en.png. Original artist: Vectorized by Simon 01:05, 2 August 2006 (UTC) Updated by Time3000 17 April 2007 to use official Wikinews colours and appear correctly on dark backgrounds. Originally uploaded by Simon. • File:Wikiquote-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/fa/Wikiquote-logo.svg License: Public domain Contributors: ? Original artist: ? • File:Wikisource-logo.svg Source: http://upload.wikimedia.org/wikipedia/commons/4/4c/Wikisource-logo.svg License: CC BY-SA 3.0 Contributors: Rei-artur Original artist: Nicholas Moreau • File:Wikiversity-logo-Snorky.svg Source: http://upload.wikimedia.org/wikipedia/commons/1/1b/Wikiversity-logo-en.svg License: CC BY-SA 3.0 Contributors: Own work Original artist: Snorky • File:Wiktionary-logo-en.svg Source: http://upload.wikimedia.org/wikipedia/commons/f/f8/Wiktionary-logo-en.svg License: Public do- main Contributors: Vector version of Image:Wiktionary-logo-en.png. Original artist: Vectorized by Fvasconcellos (talk · contribs), based on original logo tossed together by Brion Vibber • File:William_Herschel01.jpg Source: http://upload.wikimedia.org/wikipedia/commons/3/36/William_Herschel01.jpg License: Public domain Contributors: National Portrait Gallery: NPG 98 Original artist: Lemuel Francis Abbott

7.12.3 Content license • Creative Commons Attribution-Share Alike 3.0