Educational Product EaTeachers Grades K-12
NASA-EP-33 8 Solar System Litho! IS~~SOIII\3 for Earth and Space Science
This set contains the following materials:
Our Star-The Sun Mercury Venus Earth Moon Mars Jupiter Saturn Uranus Neptune Pluto Asteroids: Ida with Moon and Gaspra (Inset) NASA Resources for Educators Electronic Resources for Educators
National Aeronautics and Our Star - The Sun @ Space Administration Our Star The Sun 7 National Aeronautics and - Space Administration v
The Sun is a huge, bright sphere of mostly ionized gas the Sun. Temperature steadily increases with altitude degrees K. The process that heats the corona is.very about 5billionyears old. The closest star to Earth, it is 16 up to 50,000 K, while density drops to 100,000 times mysterious and poorly understood, since the laws of million km distant (this distance is called an Astronomi- less than in the photosphere. Above thechromosphere thermodynamics state that heat energy flows from a cal Unit). The next closest star is 300,000 times further lies the corora ("crown"), extending outward from the hotter to a cooler place. Mysterious phenomena, such away. There are probably millions of similar stars in the Sun in the form of the "solar wind" to the edge of the as this, are studied by researchers in NASA's Space Milky Way galaxy (and even more galaxies in the Uni- solar system. The corora is extremely hot -millions of Physics Division. vem), but the Sun is the most important to us because it supports life on Earth. It powers photosynthesis in green plants and is ultimately the source of all food and fossil fuel. The Sun's power causes the seasons, the climate, the Fast Facts SignmCant Dates cumnts in the ocean, the circulation of the air, and the weather in the atmosphere. Spectral Type of Star G2 V 585 BC First solar eclipse successfully predicted The Sun is some 333,400 times more massive than 1610 Galileoobservessunspdswithhistelescope 4.5 Billion Years Earth (mass= 1.99 x 1030 kg), and contains99.86% of the Age 1650-1715 Maunder Sunspot Minimum discovered mass of the entire solar system. It is held together by Mean Distance to Earth 150 Million Kilometers 1854 Fust connectionmade between solar activity gravitational attraction, producing immense pressure Rotation Period (at equator) 26.8 days andgeomagneticactivity and temperature at its core (more than a billion times Radius 695poO Kilometers Helium lines first observed in solar spectrum that of the atmosphere on Earth, and a density about First measurenent of of magnetic fields 160 times that of water). Mass 1.99 x 1030 Kilograms taken At the core the temperature is 16 million degrees K, Composition Hydrogen 7196, Helium 26.596, First radio emission from Sun observed which is sufficient to sustain thermonuclear fusion Other 2.5% First observation of solar ultraviolet using a reactions. The released energy prevents the collapse Temperature sounding- of the Sun and keeps it in gaseous form. The total Effective Surface l,OMI,OMIKtemperatureofmrona discovered energy radiated is 383 billion trillion kilowatts/sec- Energy Output (Luminosity) viacodspectralines ond, which is equivalent to that generated by 100 Solar Constant First observation of solar x-rays using a billion tons of TNT exploding each second. Inclination of Solar Equator to Ecliptic 7.2S0 sounding- In addition to the energy-producing solar core, the Galactic dcrays found to change interior has two distinct regions: a radiative and a in intensity with the 11-year sunspot cycle convective zone. From the edge of the core outward, ~argestohewed solar &re occukd - first through the radiative and then through the con- About the Image- First direct observations of solar wind made vective zone, the temperature decreases from 8 million byMariner2 to 7,000 K, and density decreases from 20 gm/cm3to 4 This image of the Sun, taken January24,1992,is ztiezoed First observations of solar gamma rays made x lo-' gm/m3. It takes about 10 million years for from space at x-ray wavelengths. The image, as seen by the by Orbiting Solar Observatory 1(OS01) photons to escape from the dense core and reach the soft X-ray Telescopeon theJapan/US/UKYohkoh Mission First mammmmt of solar neutrino flux surface. (orbiting solar obserpultory), reveals the hot, three-dimen- taken Because the Sun is gaseous, it rotates faster at the sionalgeomettyof the corona across thefill disk of the Sun. Skylab obsened Sun, discovered coronal equator (26.8 days) than at the poles (as long as 35 The large bright areas are regions where the Sun's magnetic holes as days). The Sun's "surface," known the photosphere, field is so strong that it can trap hot gases even though the 1982 First observations of neutrons from a solar is just the visible 500 km-thick layer from which most ~bySolarMaxim~~(~ temperature ofthe regions arecnrer 1 million degrees K. The of the Sun's radiation and light finally escapes, and is 1-5 UlyssesfJiesoverpolarq@onsofSun dark amare ammnl holes, which are the origin ofstrermrs the place where sunspots are found. Above the photo- Rduemca sphere lies the chromosphere ("sphere of color") that of particb, called the high speed solar wind, that flozo past 1.1&!km,"BduationrlBrisltEB-l06,NASA~W~DC may be seen briefly during total solar eclipees as a Eflrtha#dthroughthesolsr~atabout700~ reddish rim, caused by hot hydrogen atoms, around ptr=f"'d* A National Aeronautics and J Space Administration Mercury 9 - National Aeronautics and Space Administration Mercury 9
Mercury is the planet closest to the Sun. Of all the planets, the planet. Mercury also has experienced a unique Caloris basin was formed by collision of a gigantic asteroid it has the most elliptical orbit, except for Pluto. Because of geological history which has resulted in a global system of with Mercury. The strong shock wave produced by the its elliptical orbit, Mercury's closest distance to the Sun is fractures caused by shrinkage of the planet. impact traveled through the planet to instantaneously form the only 46 million km while its greatest distance is 70 million hilly, lineated terrain on the opposite side of the planet. krn. Another unique aspect of Mercury is its rotational and Soon after the planet formed it nearly melted from decay of Afterward, eruption of lava within and surrounding the orbital period. Mercury rotates on its axis once every 58.9 radioactive elements and the inward migration of iron that Caloris, and other large basins formed the smooth plains. days and circles the Sun once every 87.9 days. As a result formed its enormous core. This led to the expansion of the Over the next half billion years the core and mantle began to Mercury rotates exactly three times around its axis for planet and extensive fracturing of the surface which cool, Mercury's radius decreased by about 2 to 4 km, and the every two orbits around the Sun. If you wanted to stay up provided an exit for lava to reach the surface and form the crust was subjected to compressive stresses that resulted in a for a solar day on Mercury (sunrise to sunrise), you would smooth plains within and between the craters. At about the unique global system of fractures. As this occurred, volcan- be awake for two Mercurian years (a total of 176 Earth same time and like the other planets, Mercury was subjected ism ceased when compressive stresses in the lithosphere days.) Because Mercury is so close to the Sun, its surface to heavy bombarded by asteroidal and cometary debris left became strong enough to close off magma sources. Since that temperature has the greatest temperature range of any over from accretion of the solar system. During this early time, only occasional impacts of comets and asteroids have planet or satellite in the solar system. The surface tempera- ~eriodof heavv bombardment. the 1300 krn diameter occurred. ture reaches a maximum of 427" Celsius on the side closest to the Sun, and - 183°C on the night side. Mercury's Significant Dates Fast Facts atmosphere is tenuous and like a vacuum. The atmosphere is composed of sodium and potassium, which is probably 1610 - Italian astronomer Galileo Galilei made first Namesake Messenger of the Roman Gods derived from the surface. While Mercury does have an telescopic obersewation of Mercury. Diameter 4878 km atmosphere, it does not have satellites. 1631 - French astronomer Pierre Gassendi made first Mean Distance from Sun 57.8 million km telescopic obervations of the transit of Mercury Mass 61100 the mass of Earth Physically, Mercury is smaller than any other planet except across the face of the Sun. Density 5.44 glcc Pluto, measuring about one-third the size of Earth. 1639 - Italian astronomer Giovanni Zupus discovered Surface Temperature However, Mercury's density (5.4 g/cm3) is about the same Mercury has phases, which is evidence that the Maximum Day Side 740" Kelvin (467" C) as Earth's; therefore, scientists assume that the planet has planet circle the Sun. Maximum Night Side 90" Kelvin (-1 83" C) an enormous iron core that composes some 75 percent of 1841 - German astronomer, Johann Franz Encke made the Rotational Period 58.6 days Mercury's diameter (42 percent of the volume). The core is first mass determination using gravity effect on the Eccentricity of Orbit 0.206 surrounded by a rocky mantle and crust only about 600 km comet Encke. Rotational Period thick. Aside from Earth, Mercury is the only terrestial 1889 - Italian astronomer, Giovanni Schiaparelli produced (1 Mercury Day) 58.6 Earth days planet with a magnetic field. Although the magnetic field the first map of Mercury's surface features. is considerably weaker than Earth's, its presence is strong 1965 - American radio astronomers Gordon Pettengill and evidence that the outer core is fluid at the present time. Rolf Dyce measured the rotation period to be about 59 days. About the Image To date the only spacecraft to explore Mercury was 1968 - Surveyor 7 took the first spacecraft picture of This false color photomosaic of Mercury is composed of images Mariner I0 in 1974-75. It imaged about half the planet on Mercury from the lunar surface. taken by Mariner 10 as it flew by the planet after the first encounter its three encounters, so half of the planet is still unexplored. 1974 - Mariner 10 made the first fly-by within 900 krn of in March 1974. The image shows the Caloris basin at the left of the Although the surface of Mercury superficially resembles Mercury. terminator surrounded and filled by younger smooth plains km that of the Moon, there are significant geological 1975 - Third and final fly-by of Mercury by Mariner 10. deposits. This 1.300 diameter impact basin formed about 4 billion years ago when a large asteroid or comet struck Mercury. differences. Like the Moon, it has heavily cratered upland References The smooth plains resemble the lunar maria, the smooth, dark lava regions and large areas of smooth plains that surround and 1. Charting the Planets, Educational Brief, EB- 11 1, NASA plains that are concentrated on the Moon's nearside. However, the fill impact basins. It also has a surface covering of porous, Headquarters, Washington, DC. 12/92. Mercurian plains display less contrast in reflectivity with heavily fine-grained soil like the lunar surface. Unlike the Moon, 2. Our Solar System at a Glance, Information Summaries, PMS crater terrain shown on the right, top and bottom than is seen Mercury's heavily cratered uplands contain large regions of 0 10-A, Jet Propulsion Laboratory, Pasadena, CA. 6191. between the lunar maria (dark)and the lunar highland (light). gently rolling, smooth plains-the major type of terrain on - National Aeronautics and Venus Q Space Administration National Aeronautics ands-- - - V~~US9 Space Administration
At first glance, if Earth had a twin, it would be nus. Magellan began a fourth 243day cycle-a global the remaining surface areas. Because no rainfall, oceans, Venus. The two planets are similar in size, mass, com- gravity survey-on September 15,1992. This survey will or strong winds exist on Venus, little erosion occurs. position, and distance from the Sun. But the twins' help scientists map the internal structure of Venus. From data returned by Magellan, scientists will cre- similarities end there. Venus has no oceans, and its Magellan is unveiling on Venus a tortured surface ate and study maps of Venus for years to come. With scorching surface temperature of about 484 "C (900 OF) shaped by a history of geological violence, tectonic defor- Venus' face unveiled, we now have a better under- could melt lead. Venus hides behind a persistent glo- mation, volcanism, and impact cratering. At least 85 standing of Earth's fraternal twin, and a store of infor- bal shroud of sulfuric acid clouds in an atmosphere percent of Venus is covered by volcanic nxk-mostly mation that will help us understand the evolution of composed mostly of carbon dioxide. The atmosphere lava flows that form the planet's vast plains. Mountains our own planet. is so dense that it crushes down on the planet's surface deformed by repeated geologic activity cover much of with a pressure equal to that found at 3,000-foot depths in Earth's oceans. Oddly, Venus rotates in a direction opposite that of Earth, which means that if you were standing on Venus, you would see the Sun rising in the Significant Dates west and setting in-the east. Venus' sluggish rotation Namesake Roman Goddess of Love and Beauty 1962 - Mariner 2 (U.S.) flew by Venus (12/14/62); veri- makes one Venus "day" last as long as 243 Earth days. Distance from Sun 108.2 Million Kilometers fied high temperatures Because of its convenient orbit and scientific interest, 1970 - Vm7 (U.S.S.R) soft landed on Venus Venus has been visited by more spacecraft, both U.S. and Period of Revolution (1 Venusian Year) 0.62 Earth Years 02/15/70) Russian, than any other planet, with flyby missions, 1972 - Venera 8 (U.S.S.R) landed on Venus (7/22/72); orbiters, surface landers, and even atmosphere-floating Equatorial Diameter 12,100 Kilometers transmitted nearly an hour of data balloons. In 1962, the U.S. launched Mariw 2, the first Atmosphere (Main Component) Carbon Dioxide 1974 - Mariw 10 (U.S.), bound for Mercury, flew by successful probe to fly by another planet. Mariw 2's Inclination of Orbit to Ecliptic 3.4" Venus (2/5/74); tracked global atmospheric flyby verified Venus' high temperatures. Since then, Eccentricity of Orbit .007 circulation with visible and ultraviolet imagery there has been a series of successful space-flight missions Rotation Period 1975 - Vm9 (U.S.S.R) sent the first surface pictures to Venus (see "Sigruficant Dates"), revealing more and (1 Venusian Day) 243 Earth Days (Retrograde) of Venus via its orbiter (10/22/75) more about the cloud-veiled planet. Inclination of Axis 1772" 1978 - Pionaer Venus Orbiter(U.S.) radar mapped Venus Despite the wealth of valuable data given to us by (12/78); PhewVenusMultipbe (U.S.) dropped these missions, we still had only a rough sketch of the face four probes through Venusian clouds. of Venus. The Pioneer Venus and Venera spacecraft were .-- 1983- Venem15 6 16 (US.S.R) provided hi&-resolu- able to image the surface with radar, thus answering I tion ma~~ineradar and ~tmosDheri~analvses many of our questions about Venus' large-scale surface 1984 - Veps1 '6'2 &.s.s.R.)dropped'off landers and features,but many more questions remained unanswered About the Image balloon probes at Venus while en route to about the extent to whichVenus' surfacehas been shaped Halley's comet by volcanoes, plate tectonics, impact craters, and water This mosaic of Venus was composed from Magellan images taken 1989 - Magellan (U.S.) was launched toward Venus and wind erosion. To address these questions, NASA, in during radar investigations from 1990-1994, centered at 180" east longitude. Magellan spacecrafr imaged more than 98% of Venus' (5/4/89) 1989, launched a new radar imaging spa-aft named 1990 - Magellan arrived at Venus (8/10/90) Magellan. It was named after the early Portuguese ex- surface at a resolution of about 100 meters. This image has an egective resolution of about 3 kilometers. Gaps in the Magellan plorer Ferdinand Magellan, whose fleet was the first to coverage were filled with images from Earth-based Arecibo radar &rumnavigate Earth. in a region roughly centered at O0 latitude and longitudc and near Refame8 Magellan began its radar mapping on September 15, 1. "Charting the Planets" Educational Brief EB-111, NASA Headquarters, the south pole. This mosaic was color-codcd to represent elevation. Waahhgton, DC. 12/92. 1990. Within 243 Earth days, the spacecraft had achieved Missing elevafa'ondata from the Magellan radar altimeter were 2. "Mpsellan: Revealing the Face of Venus," JPL 400-494.Jet Propulsion and wen exceeded its primary objective: to map 70 filled with altimetryfrom the Venem spacecraft and the U.S. Laboratory, Pasadena, CA. 3/93. &no& 3. "Our Sdu Syrkm: A Geologic S~p8hot,~NP 157, NASA HcPdquutars, / percent of the planet's surface. After three complete Pioneer Vnurs missions. Brown areus rough terrain; the Wu)hing&m,DC. 5/92. 243-day cycles, Magellan had mapped 98 percent of Ve dark blue areas are smooth swf(u:es or possibly area covered with dwt. d~ationalAeronautics and Space Administration Earth - ---. - National Aeronautics and Space Administration Earth $
Earth, our planet, is the only planet in the solar system constituents. Earth's atmosphere shields us from nearly all above our planet's magnetic poles. These air molecules known to harbor life. All of the things we need to survive harmful radiation coming from the Sun, and protects us then begin to glow and are known as the auroras, or the are provided under a thin layer of atmosphere that separates from meteors as well-most of which bum up before they Northern and Southern lights. us from the uninhabitable void of space. Earth is made up can strike the surface. Satellites have revealed that the of complex, interactive systems that are often unpredict- upper atmosphere, which was thought to be calm and Our planet's rapid spin and molten nickel-iron core give able. Air, water, land, and humans themselves combine uneventful, actually swells by day and contracts by night rise to a magnetic field, which the solar wind distorts into a forces to create a constantly changing world that we are due to solar activity. The upper atmosphere contributes to teardrop shape. The solar wind is a stream of charged striving to understand. Earth's weather and climate and protects us from the Sun's particles continuously ejected from the Sun. The magnetic harmful ultraviolet radiation. field does not fade off into space, but has definite boudaries. NASA, in partnership with other U.S. and international agencies, has been studying Earth as an integrated system. Besides affecting Earth's weather, solar activity gives rise to As you observe Earth's finite boundaries, depicted on the Viewing Earth from the unique perspective of space a dramatic visual phenomenon in our atmosphere. When front of this lithograph, consider the many unanswered provides the opportunity to see Earth as a whole. Scientists charged particles from the solar wind become trapped in questions and discoveries yet to be made on our own, home around the world have discovered many things about our Earth's magnetic field, they collide with air molecules planet. planet by working together and sharing their findings. Some facts are well known. For instance, Earth is the third planet from the Sun, and the fifth largest in the solar Fast Facts Significant Dates system. Earth's diameter is just a few hundred kilometers Equatorial Diameter 12,756 km Sputnik 1 (USSR) became the first artificial satellite larger than that of Venus. Our planet rotates on its axis at a Mean Distance from Sun 1.52 X lo8km of the Earth. surface speed of approximately 0.5 km/sec at mid-latitudes, Mass 5.976 X 1023 kg Luna 1 (USSR) was the first successful mission to the while orbiting the Sun at a speed about 30 kdsec. We Density 5.52 g/cm3 Moon and the first spacecraft to leave Earth's gravity. experience these motions as the daily routine of sunrise and Mean Orbital Velocity 29.79 kds NASA launched TIROS I, the first weather satellite. sunset and the slower change of the seasons. The four Tit of Equator to Orbit 23.45" Vostok 1 (USSR) carried the first human, Yuri seasons are a result of Earth's axis of rotation being tilted Rotational Period 23.93 hours Gagarin, into space. Alan Shepard became the first more that 23 degrees. Eccentricity of Orbit 0.0 17 U.S. astronaut in space. Number of Satellites 1 John Glenn, Jr. was the first American to orbit Earth. The changing nature of the planet's systems are the Orbit Period 365.26 days Nimbus I began a series of missions to study Earth's mysteries that scientists study today. For instance, the atmosphere, geology, and oceans. North American continent continues to move west over the First humans to orbit the Moon (U.S.). Pacific Ocean basin, roughly at a rate equal to the growth About the Apollo 11 (U.S.) became the first manned lunar are of our fingernails. We made aware of this movement This Apollo 10 view of Earth was taken during a journey to landing. when it is interrupted by earthquakes. Scientists noticed a the Moon in May, 1969. While clouds obscure the Yucatan 1972 NASA began Landsat satellite series to observe distinctive pattern to those earthquakes, leading them to Peninsula, nearly all of Mexico north of the Isthmus of Earth's land surfaces. conclude that Earth is dynamic, with its spherical surface Tehuantepec is clearly visible. The Gulf of California, Baja, 1973 Skylab, the first space station (U.S.) was launched. separated into moving caps or plates. Earthquakes result and the Sun Joaquin Valley of California are identijiable as 1976 LAGEOS I tracked movements of Earth's surface, to when plates grind past one another, ride up over one well. In the upper right comer the northern polar cap increase understanding of earthquakes and other another, collide to make mountains, or split and separate. appears with pressure fronts emanating to the south. geological activity. These movements are known as plate tectonics. Developed 1978 TOMS instrument launched on Nimbus VII, recorded within the last thirty years, this explanation has unified the continuous data on Earth's ozone layer. results of centuries of study of our planet, long believed to For more information on planet Earth, access NASA Spacelink- 1984 Earth Radiation Budget Satellite began studies of be static. NASA's electronic information system designed to provide current Earth's reaction to Sun's energy. educational information to teachers, faculty, and students. 199 1 UARS comprehensive data on chemistry and Oceans at least 4 km deep covers nearly 70% of Earth's physics of the atmosphere provides evidence that surface. Water exists in the liquid phase only within a Access by computer through directdial modem or the Internet: human-made chemicals are responsible for the narrow temperature span (0 degrees to 100 degrees C). Modem line: (205) 895-0028 Antarctic ozone hole. This temperature span is especially narrow when contrasted Terminal emulation: VT-100 required 1992 TOPEXJPoseidon satellite details links between with the full range of temperatures found within the solar Data format: 8-N- 1 Earth's oceans and climate. system. 'Ihe presence and distribution of water vapor in the Telnet: spacelink.msfc.nasa.gov 1998 NASA will launch first satellite of Earth Observing atmosphere is responsible for much of the Earth's weather. World Wide Web: http~/spacelink.msfc.nasa.gov System (EOS) series, continuing through the first decade of 2 1st century. On the surface, we are enveloped by an ocean of air that Gopher: spacelink.msfc.nasa.gov consists of 78% nitrogen, 2 1% oxygen, and 1% other Anonymous FIP spacelink.msfc.nasa.gov Internet TCPIP address: 192.149.89.61 National Aeronautics and Moon 0 Space Administration -- - -.
1- 1- National Aeronautics and - + . - - -. -- -+- +. -- - --A --.- ---. --.+ - - . Moon 0 ' Space Administration
Earth's only natural satellite, the Moon, is unusually planet-wide magnetic field; the Moon lacks Earth's mol- cular maria. These "mascons" (mass concentrations) are large in relation to its planet, having a diameter roughly ten core. thought to be caused by layers of denser, basaltic lavas 1/4 that of Earth's. Thus, the two bodies are sometimes The Moon's shape is unusual. It is slightly egg- that fill the mare basins. referred to as a double-planet system. This situation sug- shaped, with the small end of the "egg" pointing toward Much remains to be learned about our Moon, begin- gests an unusual origin for the Moon. Some proposed Earth. This position causes the Moon to keep the same ning with its origin. Active research still continues to origin theories include separation from Earth, indepen- face toward Earth at all times. The far side, which cannot yield information about our nearest neighbor in space dent formation, and capture from elsewhere in the solar be observed from Earth, has days and nights just like using the samples and data returned by Apollo and other system. The theory that seems to explain most of our those on the near side. The lunar gravity field is also missions. Speculation has begun on how the Moon observations, however, is that a Mars-sized body once hit unusual. A surprising discovery from the tracking of the might be used to support lunar bases and other human Earth and the resulting debris (from both Earth and the Lunar Orbiter photographic spacecraft revealed strong ar- activities in the next century. impacting body) accumulated to form the Moon. What- eas of high gravitational acceleration located over the cir- ever the origin, we know the Moon was formed over 4.5 billion years ago (the age of the oldest collected lunar rocks). Fast Facts Significant Dates During the Moon's formation, very high temperatures caused extensive melting of its outer layers. The melting Diameter 3,476 Kilometers 1610 - Italian astronomer Galileo Galilei made the resulted in the formation of the lunar crust, probably Mass 1/81 the Mass of Earth first telescopic observations of the Moon from a planet-wide "magma ocean." The rocks found on Density 3.3 Grams/Cubic Centimeter 1959 - Soviet spacecraft Luna 2 reached the Moon, im- pacting near the crater Autolycus the Moon's highlands are at least 4.5 billion years old, Rotation Period 27.3 Days and are rich in light-colored minerals, called feldspar. 1961 -President John F. Kennedy proposed a Surface Gravity 1/6g These rocks, called anorthosites, give the lunar highlands manned lunar program their bright color. In the years since they were formed, Escape Velocity 2.4 Kilometers/Second 1964 - Ranger 7 produced the first close-up TV pic- innumerable meteorites have hit the Moon, producing a Oldest Rocks 4.5 Billion Years tures of the lunar surface crust that is intensely cratered and fragmented. Atmosphere None 1966 - Luna 9 made the first soft landing on the Moon About 4 billion years ago, a series of major impacts 1967- Lunar Orbiter missions completed photo- occurred, forming huge craters. These craters are now graphic mapping of the Moon (begun in 1966) the sites of basins called maria (e.g., Mare Imbrium, Mare 1968 - Apollo 8 made the first manned flight to the Serenitatis). Between 4 and 2.5 billion years ago, volcanic Moon, circling it 10 times before rArning to activity filled these basins with dark-colored lavas, called About the Image Earth basalts. After this time of volcanism, the Moon cooled 1969 - Apollo 11 mission made the first landing on the down, and has since been relatively inactive, except for This photograph of the Moon was taken in December 1972 Moon and returned samples the occasional "hits" of meteorites and comets. The by the Apollo 17 mission, shortly after the spacecraft left 1972 - Apollo 17 made the last manned landing of the Moon has not undergone the continual mountain-build- the Moon to return to Earth. The view shows the full Apollo Program ing and volcanic activity that characterize Earth; it is a Moon. The region at the right (about two-thirds of the 1976 - Soviet Luna 24 returned the last sample of the fossil planet on which the earliest stages of geologic evo- total) is part of the Moon's far side, the side never seen Moon lution are preserved. from Earth. The dark regions are the maria, which are 1990 - Galileo spacecraft obtained multispectral im- The Moon, however, is not completely dead. Seis- covered with dark-colored basalt lava flows. The dark, ages of the western limb and part of the far mometers emplaced by the Apollo astronauts have re- nearly circular mare region at the upper left is called Mare side of the Moon corded small earthquakes (more properly called "moon- Crisium. Below it and to the left is Mare Fecunditatis, 1994 - Clementine mission conducted multispectral quakes") at depths of several hundred kilometers. The with the large white crater Langrenus. The light-colored mapping of the Moon quakes are probably triggered by tides caused by Earth. regions are the lunar highlands, which are made of older rocks and contain extensive large craters made by large References Small eruptions of gas from some craters, such as 1. Our Solar System: A Geologic Snapshot, NP 157, NASA Headquarters, Aristarchus, have also been reported. We know the deep projectiles that struck the Moon more than 4 billion years Washington, DC. W92. interior of the Moon is still hot, and perhaps partially ago. The bright, rayed crater near the upper-right rim is 2. Information Summaries: Our Solar System at a Glance, PMS 010-A, Jet Propulsion Laboratory, Pasadena, CA. 6/91. molten. Although there are local magnetic areas in the Giordano Bruno, a fresh crater fomed by a much younger 3. Apollo Expeditions to the Moon, NASA SP-350, NASA Headquarters, r lunar crust associated with some craters, there is no imvact event. I Washington, DC. 1975. HqL-381 1/94 National Aeronautics and Space Administration Mars National Aeronautics and Space Administration Mars
Mars-the Red Planet, the Bringer of War-has hot lava pushing upwards through the crust to the Mons (27 krn high and 600 km across), in the solar inspired wild flights of imagination over the centu- surface. Periodically great dust storms occur that system; volcanoes in the northern Tharsis region that ries, and an intense scientific interest. Fancied to be engulf the entire planet. The effects of these storms are so huge they deformed the planet's sphericity; and the source of hostile invaders of Earth, the home of a are dramatic, including dunes, wind streaks, and wind a gigantic equatorial rift valley, the Vallis Marineris. dying civilization, and a rough-and-tumble mining carved features. This canyon system could easily fit the Grand colony of the future, Mars has proven to be fertile Canyon inside it and stretches the distance equivalent ground for science fiction writers, based on seeds Mars has some remarkable geological characteristics from New York to Los Angeles. planted by centuries of scientific observation. Mars including: the largest volcanic mountain, Olympus has shown itself to be most Earth-like of all the planets; it has polar ice caps that grew and receded with the change of seasons, and markings that Significant Dates Fast Facts looked, through 19th century telescopes, to be similar Namesake Roman God of War 1965 - U.S.A. Mariner 4 made first close-up pictures of the to human-made water canals on Earth, which fueled Distance from Sun surface during flyby. speculations that Mars was inhabited. Maximum 249 million km 1969 - U.S.A. Mariner 6 and Mariner 7 flybys resulted in Minimum 206 million km high-resolution images of the equatorial region and American and Russian orbiters did not disclose any Distance from Earth southern hemisphere. canals on Mars, but did find evidence of surface Maximum 399 million km 1971 U.S.A. Mariner 9 first satellite to orbit another erosion and dried riverbeds, indicating the planet was - Minimum 56 million km planet. once capable of sustaining liquid water. For millions Rotational Period 24.6 hours 1973 - U.S.S.R. Mars 3 and Mars 5 first attempt to land on of years, the Martian surface has been barren of Equatorial Diameter 6,786 km Mars. water, and not subjected to the erosions and crustal Equatorial Inclination to Ecliptic 25.2" plate movement that continually resurface Earth. 1976 - U.S.A. Viking I orbited Mars. Lander provided first Gravity 0.38 of Earth's Mars is too cool and its atmosphere is too thin to sustained surface science. U.S.A. Viking 2 lander Atmosphere allow liquid water to exist. There is no evidence of discovered water frost on the surface. Main Component Carbon Dioxide civilizations, and it is unlikely that there are any 1988 - U.S.S.R. probe Phobos returned detailed pictures of Pressure at Surface -8 millibars (vs 1,000 on Earth) extant life forms, but there may be fossils of life- Phobos. forms from a time when the climate was warmer and Temperature Range -143OC to +17OC there was liquid water. Moons (2) Phobos (Fear), 2 1 km diameter Deimos (Panic), 12 km diameter Mars is a small rocky planet that developed relatively About the Image Rings None Orbital Eccentricity close to the Sun that has been subject to some of the Thisfill-disk view of Mars is a merge of a morphologic mosaic and 0.093 same planetary processes associated with the a colorhrightness mosaic taken by Viking Orbiter I in 1980. The Orbital Inclination to Ecliptic 1.85" formation of the other "terrestial" planets (Mercury, view centers at 20°N, 60%'. Note the north pole residual ice cap Magnetic Field Density To be determined. Very Venus, and Earth), including: volcanism, impact (top). Tharsis Montes (lefr),chaotic terrain, and Chryse outflow weak, if any. events, and atmospheric effects. Unlike Earth, Mars channels (NE of Valles Marineris). Kasei Valles appears at the retains much of the surface record of its evolution. center of Mars. The large dark region NE of Kasei Valles is Layered terrains near the Martian poles suggest that Acidalia Planitia. Valles Mariners (bottom center) is a canyon the planet's climate changes have been periodic, system that stretches over 5,000 km in length and up to 8 km in References depth. North of the eastern end of the Valles Marineris is the 1. Discovering Mars, PAM-537. NASA Headquarters, Washing- perhaps caused by a regular change in the planet's Chryse Planitia where Viking 1 landed. West of the Valles ton, DC.9/94. orbit. Martian tectonism-the geological development Marineris lie three of Mars' huge volcanoes, the Tharsis volcanoes, 2. The Exploration of Mars, EB-112, Educational Brief, NASA and alteration of a planet's crust-differs from Earth's. which appear as dark reddish spots. Each volcano is about 27 km Headquarters, Washington, DC. 5/93. Where Earth tectonics involve sliding plates that high, over 350 km in diameter, and has a central crater at its 3. Charting the Planets, EB-111, Educational Brief, NASA grind against each other or spread apart in the summit. To the upper left of these three huge volcanoes is the most Headquarters, Washington, DC. 12/92. seafloors, Martian tectonics seem to be vertical, with famous member, Olympus Mons, which is about 600 km across. National Aeronautics and Jupiter 1 Space Administration National Aeronautics and Jupiter 3 Space Administration
Jupiter reigns supreme among the nine planets, about atmospheric effects and interactions that are nature and source of this ring are among the questions containing two-thirds of the planetary mass of the subtle on Earth, such as magnetosphere-atmosphere to be answered by subsequent missions to Jupiter. solar system. In composition it resembles a small star. interactions. Subsequent missions to Jupiter will help On October 18, 1989, NASA launched the Galileo Its interior pressure may reach 100 million times the us understand the chemistry and behavior of Earth's spacecraft to Jupiter. After flying by Venus and Earth surface pressure on Earth. Jupiter's magnetic field is own relatively thin, but very precious, atmosphere. (Earth twice), and passing through the asteroid belt, immense, even in proportion to the size of the planet, Sixteen Jovian moons have been discovered. Some Galileo will arrive at Jupiter in December 1995. Galileo stretching millions of miles into the solar system. Elec- are icy, some rocky, some cratered, and some smooth. will investigate the chemical composition and physi- trical activity in Jupiter is so strong that it pours bil- 10, the fifth moon from Jupiter,is actively volcanic. The cal state of Jupiter's atmosphere; will characterize the lions of watts into Earth's own magnetic field every Voyager flybys witnessed a total of nine spectacular morphology, physical state, and dynamic properties day. volcanic eruptions, the first time any such geologic of the Jovian satellites; and will analyze the structure Dynamic Jupiter is endowed with 16 moons, a ring activity had been seen outside of the Earth. and physical dynamics of the Jovian magnetosphere. system, and an immense, complex atmosphere. Its The Voyagers also revealed a thin ring around Jupi- The data obtained from Galileo will undoubtedly revo- atmosphere bristles with lightning and swirls with ter. Composed of three bands, the ring is optically lutionize our understanding of the complexities of huge storm systems, including the Great Red Spot dark, suggesting it is made up of impact debris. The Jupiter and the Jovian system. (giant "eye-looking" feature at lower-left of image), a storm that has persisted for at least 100--and perhaps as long as myears. Some scientists theorize that Significant Dates beneath the atmosphere there is no solid mass at the Namesake King of the Roman Gods 1610 - Italian astronomer Galileo Galilei discovered center of Jupiter,but that the planet's unique tempera- Distance from Sun 778.3 Million Kilometers four moons orbiting Jupiter (10, Europa, ture and pressure conditions sustain a core whose Period of Revolution Ganymede, and Callisto-theGalileanSatellites) density is more like liquid or slush. (1 Jovian Year) 11.86 Earth Years 1973- Pionaer 10 passed within 130,354 km of Jupiter In March 1972, NASA launched the Pioneer space- Equatorial Diameter 143,200 Kilometers (12/3/73); cloudtops and moons imaged craft to observe the asteroid belt and Jupiter. Arriving Atmosphere (Main Components) Hydrogen 1974 - Pionaer 1 I passed within 43,000 km of Jupiter at Jupiterin December 1973, Pioneer 10 revealed Jupiter's and Helium (12/2/74); first images of polar regions intense radiation output, its tremendous magnetic field, Moons (16) In Ascending Distance from Planet: 1979 - Voyager 1 passed within 350,000 km of Jupiter and the probability of a liquid interior. One year later, Metis, Adrastea, Amalthea, Thebe, 10, (3/79); discovered faint ring and three moons Pioneer 11 flew by Jupiter on its way to Saturn, provid- Europa, Ganymede, Callisto, 1979 - Voyager 2 passed within 650,000 km of Jupiter ing even more detailed imagery and measurements, Leda, Himalia, Lysithea, Elara, (7/79); provided detailed imagery of Jovianring including our first close-up look at the giant planet's Ananke, Carme, Pasiphae, Sinope and 10 volcanism polar regions. Then, in August and September 1977, Rings 1 1989 - Gdileo spacecraft launched (10/18/89) NASA launched the two Voyager spacecraft to the Inclination of Orbit to Ecliptic 1.3" 1995 -Galileo to arrive at Jupiter 02/7/95) outer solar system. The Voyagers' 1979encounters with Eccentricity of Orbit .048 RefemKa Jupiter provided us with startling, beautiful imagery, Rotation Period (1 Jovian Day) 9 Hours 55 Minutes 1. Pi#.owlinBJupiter," PAM-540, NASA Headqmtem, W- DC. 6/93. revealing thousands of features never before seen. Inclination of Axis 3°F 2 Galileo Fact Sheet, NASA Headquartem, Washington, DC. 3/92. 3. "Qllutine th Planets" Educational W EB-111, NASA Hcedquahs, Warh- Swirling multicolored turbulencesurrounded theGreat ington, DC.12/92. Red Spot. Rising plumes and spinning eddies formed and dissipated, suggesting a strong source of heat bubbling up from within the planet. About the Image Voyager imagery told us that Jovian dynamics were This pt.ocessed wlor image ofJupitermproduced in 1990 by the U.S.Geological Sumyfrom a Voyager image captured in 1979. extremely complex. Yet many of these features re- Thewh haw been enhanced to bring out detail. Zones oflight-colored,ascendingcloudsalternate with bvmds ofdark,descending semble effects we know of in our own atmosphere, clouds. The clouds traael amnd the planet in alternating aastzmrd and wlesfmrd belts at spais of up to 540 kibmehper hour. magnified by the enormity and extremity of the Jovian Tremendous storms as big as Earthly continents surge mndthe planet. The GWRed Spot (dshape toward the laww-w) environment. In studying Jupiter, we can learn more is an enormous- anticyclonic storm that drips along its belt, eventually circling the entire planet. National Aeronaut~csand Saturn Y Space Admin~stration h National Aeronautics and Space Administration - --.- Saturn b
Saturn, the sixth planet from the Sun, is one of the spacecraft discovered hundreds of ringlets within Earth's was like long ago. Further study of this moon five planets visible from Earth without a telescope. Saturn's major rings. Some ringlets were found to be promises to reveal much about planetary formation, Since the 17th century, when Saturn's dazzling, com- "braided," some had small moons flanking them and perhaps about the primordial Earth as well. plex ring system was first observed by the Italian (called "shepherding" moons), and all gave the Cassini, a joint U.S.-European orbiter/probe mis- astronomer Galileo Galilei, the planet has stood as a impression of great dynamism. Shadowy "spokes" sion to Saturn and Titan, will be launched in October symbol of the majesty, mystery, and order of the were seen to develop and dissipate in the rings. Ring 1997, arriving at the Saturnian s stem in 2004. physical universe. Over the past 20 years, we have particles were found to be composed mostly of ice Cassini's 4-year scientific mission is 2'ual: to complete discovered that Jupiter, Uranus, and Neptune also crystals, and to range in size from a few centimeters to a multispectral, orbital surveillance of Saturn, and to have rings; however, Saturn's ring system is the most a few meters. investigate Titan. Cassini will measure the planet's extensive and brilliant. Although the origin of the Today we know Saturn to have 7 major ring divi- magnetosphere, atmosphere, and rings, and observe rings is unknown, scientists hope to uncover clues by sions and 18 moons. The rings may be the remnants of some of its icy satellites and Titan during close flybys. studying the planet's history. moons destroyed by tidal interaction with Saturn's The orbiter investi ation of Titan will be augmented A giant, gaseous planet, Saturn has an intriguing gravity. They may include remnants of comets that by an instnunentefprobe-called the Huygens Probe atmosphere. Alternate jet streams of east-west and passed too close to Saturn and were likewise -that will descend through Titan's atmosphere and west-east circulation can be traced in the motions of destroyed. Of the 18 known moons, Titan-the send back data about the atmosphere and surface. If the cloud tops; the speeds of these jet streams reach as largest-has held the attention of scientists most. A bit the Cassini mission goes as planned, theories of the much as 1,000 miles per hour, and are responsible for larger than Mercury, Titan is shrouded by a thick solar system's evolution and chemical processes on the banded ap earance of the clouds. The atmosphere nitrogen atmosphere that might be similar to what primordial Earth may be improved. consists mostP y of hydrogen and helium, but also includes trace amounts of other elements. Electrical processes and heat from internal planetary sources Fast Facts enrich the la ered chemical mix of the atmosphere, 1610 -Galilee Galilei discovered Saturn's rings which probally transitions from superheated water Namesake Roman God of Agriculture near the core to the ammonia ice clouds that are Distance from Sun 1,429.4 Million Kilometers 1659 -Christiaan Huygens discovered that Saturn's observed at the cloudtop. The planet's atmosphere Period of Revolution (1 Saturnian Year) 29.46 Years rings were separate from the planet also features storm structures similar to Jupiter's Equatorial Diameter 120,536 Kilometers 1676 -Jean Dominique Cassini discovered the Cassini famous Great Red Spot. Atmosphere (Main Components) Hydrogen and Helium division Although Galileo was the first to see Saturn's rings Moons (18) Pan, Atlas, Prometheus, Pandora, Epirnetheus, 1979 -Pioneer 11 passed within 22,000 km of Saturn's (in 1610), it wasn't until 1659 that the Dutch Janus, Mimas, Enceladus, Tethys, Telesto, Ca- cloudtops (9/1/79); first images of polar regions; astronomer Christiaan Huygens, usin lypso, Dione, Helene, Rhea, Titan, Hyperion, imaged Titan; detected presence of internal telescope, observed that the rings actua5 yan are improved separate Iapetus, Phoebe source of heat in Saturn from the planet. In 1676, the French-Italian Rings (8) D, C, B, A, F, G, E (The Cassini Division is 1980 -Voyager 1 passed within 125,000 km of Saturn's astronomer Jean Dominique Cassini first observed Visible Between the B and A Rings.) cloudtops (11 /12/80); sent back 17,500 color what appeared to be a division between the rings- Inclination of Orbit to Ecliptic 2.5" images; measured high wind speeds in Saturn's now known as the Cassini division. Improvements in Eccentricity of Orbit 0.056 equatorial region; imaged five moons; measured telescopy over the next three centuries revealed much Rotation Period (1 Saturnian Day) 10 Hours 40 Minutes Titan's size about the mysterious lanet: the banded atmosphere, Inclination of Axis 26'44' 1981 -Voyager 2 passed within 101,000 km of Saturn's the storm "spots," an‘r a very apparent "flattening" at cloudtops (8/25/81); provided detailed imagery the poles, three features Saturn was observed to share of rings; imagqi intermediate sized moons; mea- with Jupiter. About the Image sured and made compositional studies of Titan's Over the past two decades, a series of spacecraft atmosphem (see "Sigruhcant Dates") flew by Saturn, giving us our 1997-Cassini spacecraft will be launched toward the first close-up looks of the lanet, and revealing to us a This true-color image was assembled from Voyager 2 Saturnian magnetic fie1cf 1,000 times stronger than images obtained August 4,1981,from a distance of21 million Satumiansysteln Earth's. Previously unobserved rings and moons were kilometers (13 million miles) from the spacecraft. Three of 2004 -Cassini to arrive at Saturn also discovered. Some moons were found to be cov- Saturn's icy moons flethys, Dione, and Rhea) are visible at References ered with very smooth ice. Also, visible and infrared the bottom of the image. The shadow 4 Tethys appears on 1. "Discovering Saturn," PAM-541,NASA Headquarters, observations of Saturn showed a surprising of Saturn's southern hemisphere. The pastel and yellao hues on Washington. DC. 10/93. us mix 2 "Charting the Planets" Educational Brief EB-Ill,NASA Headquarters, thermal patterns among the cloud bands, suggesting the planet mlmany contrasting bright and dab bands in Washington. DC. 12/92 p- - internal processes yet to be understood. The Voyager troth hemispheres qf Saturn's waather system- 3. CPssini Fect sheet, NASA Hemiquarters, WWashington, DC. 3/93. A National Aeronautics and Uranus 6 Space Administration - L/ National Aeronautics and Uranus 0 Space Administration r
While surveying the skies on a March evening in 1781, ever, faint cloud markings between 20 and 50 '5 latitude radii, with the tiny moon Cordelia orbiting inside the English astronomer Sir William Herschel discovered the were recorded. The rotation rate of these clouds com- brightest, outermost ring. Nine other small moons orbit planet Uranus, at first mistaking it for a comet. After pared with the rotation of the magnetic field indicated from 2.1 to 3.4 Uranian radii. The five outer moons, with observing Uranus' path among the stars, astronomers de- wind speeds of 100-600 krn/hr, which, unlike the winds diameters ranging from 13 to 15 percent the size of our termined that Uranus8orbit extends 19 times farther from of Jupiter and Saturn, blow westward. Moon, revolve around the planet at distances from 4 to the Sun than Earth's orbit. Although the diameter of the In 1977, Uranus was observed passing in front of a 15 radii, or one-third to one-and-a-half times the distance planet is four times greater than that of Earth, at this dis- star. hving this observation, it was revealed that Uranus between Earth and our Moon. Voyager 2 revealed that tance it appears in the sky as a faint disk spanning one possesses a system of at least 11 thin, widely, separated a remarkable variety of surface features mark these larger thousandth of a degree, making it barely visible to the rings. In 1986, Voyager 2 confirmed the rings' existence. satellites, including craters, fractures, and frozen water. unaided eye only on clear, dark nights. Today, we know that the dimly lit Uranian system Because no missions are currently being planned to Early astronomers observed that the orbits of the four consists of a planet surrounded by a flat system of rings return to Uranus, future information will need to be then-known Uranian moons were tipped 98 degrees rela- and satellites. Bits of debris are concentrated into thin tive to the planet's orbit around the Sun. These satellites, gained using ground-based or Earth-orbiting facilities. rings that orbit the planet between 1.4 and 2.0 Uranian as well as Miranda (a Uranian moon discovered in 1948), and 10 small inner moons discovered by Voyager 2 in 1986 -- - (bringing the total number of Uranian moons to 151, all lie in Uranus8equatorial plane. Significant Dates Fast Facts Tipped Uranus behaves as a giant top as it spins on an 1781 - Sir William Herschel discovered Uranus Namesake Roman God, Father of the Titans axis almost in the plane of the orbit. This motion leads to extreme seasonal variation in what sunlight is available. 1787 - Sir William Herschel discovered Uranian Distance from Sun 2.871 Billion Kilometers Over the period of 1 Uranian year (84 Earth years), the moons Titania and Oberon Period of Revolution polar regions of the planet go through four seasons, as on 1851 - William Lassell discovered Uranian moons Urkan 84.01 Earth Years Ariel and Umbriel Earth, with perpetual sunlight in the summer, and total Equatorial Diameter 51,118 Kilometers darkness in the winter. Periods of alternating day and 1948 - Gerard Kuiper discovered Uranian moon night are interspersed in the spring and fall. Miranda Atmosphere @lainCOmPOnenb) Hydrogen and Helium With winters and summers extending for 21 Earth 1977 - lames Elliot and others discovered the rina" of I years, it would seem that Uranus should experience dras- Uranus Moons (15) In Ascending Distance from the Planet: tic temperature changes, but this is not the case. Uranus 1986 - Voyager 2 discovered 10 small moons, detected Cordelia, Ophelia, Bianca, Cressida, is so far from the Sun that its energy input per area is 360 the magnetic period, and measured the length Desdemona, Juliet, Portia, Rosalind, times less than that on Earth; thus, little heating occurs of the rania an day. Puck, during the summer. The rate of heat loss depends on the Belinda, Miranda, Ariel, temperahue of the region that is exposed to space; low Umbriel, Titania, Oberon cloud temperature leads to little heat loss during the win- About the Image Rinw ter. Despite Uranus8 strange seasons, the temperature of Inclination of Orbit to Ecliptic the clouds shrouding the planet remain somewhat con- This color image of Uranus was pruduced in 1986 by Eccentricity of Orbit stant at -220 T. Only one spacecraft has observed Uranus at close the Jet Propulsion Laboratory. Images obtained with Rotation Period range-Voyvlger 2. The Voyager spacecraft revealed that blue, green, and orange filters were combitzed and the (1 Uranian Day) 17 Hours 14 Minutes reaming patterns in radio signals from the planet indi- wlor balance adjusted to simulate what the eye would Inclination of Axis 97.86" cated a rotation period (length of day) of 17.3 hours. Voy- mllysee. The blue wlor is due to the absorption of ager scientists also discovered that, while the strength of red and omnge light by methane gas in the planet's References Uranus' magnetic field is similar to Earth's, the Uranian 1.Our Solar System: A Geologic Snapshot, NP 157, NASA poles are an amazing 60 degrees away from the rotational upper atmosphere. An obscuring haze gives Uranus a Headquarters, Washington, DC. 5/92. pole. bland, veluefy appeamnce. The darkening near the pe- 2. Voyager at Uranus, JPL 400-268,1986. When Voyager 2 flew by the planet, the spads rimeter of the planet is typical of back~fteringof sun- 3. Information Summaries: Our Solar System at a Glance, PMS cameras revealed an almost featureless atmosphere; how- light in a thick atmosphere. 010-A, Jet Propulsion Laboratory, Pasadena, CA. 6/91. National Aeronautics and Space Administration Neptune National Aeronautics and Space Administration Neptune Vf
The discovery of Neptune is an excellent example of the interiors of both Uranus and Neptune. Studies of radio Triton, the largest satellite of Neptune, has proven to be not application of the scientific method on an international waves caused by Neptune's magnetic field revealed the only the most intriguing satellite of the Neptunian system, scale. Astronomers discovered Neptune as a result of their length of a Neptunian day. Aurorae were detected, but but also one of the most interesting in all the solar system. efforts to understand the orbit of Uranus. Observations of much weaker than those on Earth and other planets. It shows evidence of a remarkable geologic history, with Uranus' orbit did not a;gree with theory, which led theorists active geyser-like eruptions spewing invisible nitrogen gas to hypothesize about the existence of yet another planet, Neptune is now known to have eight satellites, six of which and dark dust particles several kilometers into the tenuous well beyond Uranus which perturbed the orbit of Uranus. were found by Voyager 2. The new satellites are all small atmosphere. Triton's relatively high density and retrograde Calculations were performed to reveal the approximate and remain close to Neptune's equatorial plane. Names orbit offer strong evidence that Triton is not an original location of the hypothesized planet. Careful observations selected from mythology's water deities have been given to member of Neptune's family but is a captured object. If of this location followed by investigators at institutions in Neptune's newest satellites by the International Astronomi- that is the case, tidal heating could have melted Triton in its several countries confirmed the existence of the hypoth- cal Union. originally eccentric orbit, and the satellite might even have esized planet-Neptune. been liquid for as long as one billion years after its capture by Neptune. When Voyager 2 flew within 5,000 km of Neptune on August 25,1989, the planet was the most distant member of the solar system from the Sun. (In 1999 Pluto will once again become the most distant planet.) Neptune orbits the Fast Facts Significant Dates Namesake Roman god of the Sea Sun every 165 years, and is the smallest of the solar Distance from Sun 4,501.2 Million Kilometers Mathematicians, John Adams (British) and Jean system's gas giants. Voyager 2 solved many of the Period of Revolution 164.79 Years Leverrier (French) predict Neptune based on questions scientists had about Neptune's rings. Searches ( 1 Neptune Year) ohital motion of Uranus. for "ring arcs," or partial rings, showed that Neptune's rings German astronomer Johann Galle discovered are Equatorial Diameter 49,528 kilometers actually complete, but the thickness of the rings vary Atmosphere Hydrogen and Helium Neptune using predicted location provided by be so that they cannot fully viewed from Earth. (Main Components) Adams and Leverrier. Moons Naiad, Thalassa, Depoina, British Astronomer WIlliam Lassell discovers Even though Neptune receives only three percent as much Galatea, Larissa, Proteus, Neptune's largest satellite, Triton. sunlight as Jupiter does, it is a dynamic planet and Triton, Nereid American astronomer Gerard Kuiper discovered surprisingly showed several large, dark spots reminiscent Rings Four thin rings of varying Nereid. of Jupiter's hurricane-like storms. The largest spot, dubbed Rings of Neptune discovered by astronomers Dark thickness the Great Spot, is about the size of Earth and is Inclination of Orbit to Ecliptic 1.77 degrees based on star occultations. similar to the Great Red Spot on Jupiter. At low northern Eccentricity of Orbit 0.009 Voyager 2 discovered six small satellites: Naiad, latitudes, Voyager 2 captured images of cloud streaks Rotational Period 16.11 hours Thalassa, Despoina, Galatea, Larissa, and Proteus. decks casting their shadows on cloud below. The strongest Inclination of Axis 28.8 deerees winds on any planet were measured on Neptune. Most of the winds there blow westward, opposite to the rotation of the planet. Near the Great Dark Spot, winds blow up to About the Image 2,000 km/hr. A small irregularly shaped, eastward-moving During 1989, the Voyager 2 narrow-angle camera was used immediately to the south and east of this oval are seen to cloud was observed "scooting" around Neptune every 16 to photograph Neptune almost continuously for two Aays, substantially change their appearances in periods as short as hours or so; this "scooter" could be a cloud plume rising recording approximately two and a Mf rotations of the four hours. The smaller dank spot at the lower right of the above a deeper cloud deck. planet. This image shows two of four cloud features planet circuits Neptune every 16.1 hours. Voyager 2 tracked including the Great Dark Spot and a LCclaaoa The magnetic field of Neptune, like that of Uranus, is smaller dark spot. The image has been processed to 1. ~duk~.~Brid.EB-lll.NASAHedquuraa highly tilte~l-47~from the axis of rotation. The magnetic enhance the visibility of features, at some s&$ice of color w&angm,DC. 12192. fields of tbe two planets are similar. Scientists think tbe fidelity. l%e Great Dank Spot near the lcft side of the planet 2. ChvSdcv~mcrroGhner,Inf~Summpies.PMSOl~A,ktRoplbioll extreme oxiattttion may be characteristic of flow in the cim'ts Neptune evtry 18.3 hours. l%e bright clorrdp w National Aeronautics and Pluto p v 1 Space Administration L/ National Aeronautics and ------+*+- - 4- - -..-.-CF- -r -. --+I - 14 <----U.-- - --lu-rl Pluto p Space Administration r
Pluto is unique among the planets. It's the smallest, devoid of strong color, and there is no confirmed evi- recent discovery of several bodies approaching the size the coldest, and the farthest from the Sun. Its orbit is the dence for an atmosphere on Charon. of Charon in the region beyond Pluto has bolstered this most elliptical and tilted, and it's the only planet that has In the late 1980s' Pluto and Charon underwent a set theory. a moon so close to its own size. Because of its great of mutual eclipses in which each body passed in front of Although no spacecraft mission has been sent distance, Pluto remains the only planet that has never the other repeatedly for several years. This pattern of to Pluto, NASA is presently working with scientists been visited by spacecraft. events can be seen from Earth every 124 years, and will around the United States to discuss and evaluate plans Pluto wasn't discovered until 1930, when American next bepin 2109 AD. Based on data from these eclipses for a mission to explore this strange double planet. astronomer ClydeTombaughfirst captured it on photo- and sophisticated computer models, it was possible to According to these plans, one or two small spacecraft graphs. Because of its faintness, several decadeselapsed make crude maps of each body. From these maps it was would be launched at speeds as high as 160,000 kilome- before much was learned about Pluto. However, begin- learned that Pluto has polar caps, as well as large, dark ters per hour in 2000 or 2001, so that they could reach ning in the late 1970~~as astronomical instrumentation spots nearer its equator. Because Pluto is so small and Pluto before 2010, when the planet's atmosphere is and telescope technology began to advance rapidly, so far away, it is impossible for any telescope on Earth to expected to begm collapsing onto the surfacein a planet- did the number of things known about Pluto. direstly see these features. By getting above Earth's wide snow storm. We now know Pluto's diameter is much smaller than blurring atmosphere, the Hubble Space Telescope is was believed at its discovery. In fact, Pluto is only about capable of mapping Pluto; in 1994 the newly repaired 2,400 kilometers across, which means that Pluto is Hubble will undertake this project. Significant Dates smaller than Earth's moon! Pluto's surface, which is Today, questions such as "How were Pluto and 1930 - Pluto discovered slightly reddish, is made up of exotic snows, including Charon formed?" and ''Why are they so small and different from all the other planets?" still remain. One 1955 - Pluto's 6.4 day rdation period discovered methane, nitrogen, and carbon monoxide. Evidence 1976 - Methane on Pluto's surface discovered indicates that Pluto's interior consists primarily of rock leading theory suggests that Pluto and Charon are relics and water ice. Above the planet's surface lies an atmo- of a population of hundreds or thousands of similar 1978 - Charon discovered sphere, which is not very dense; the atmospheric pres- bodies that were formed early in solar system history. 1985 - Onset of Pluto-Charon eclipses (lasted 19s sure on Pluto is just one millionth that on Earth. Al- According to this hypothesis, most of these bodies were 1991) though the atmosphere is much more tenuous than ejected to much larger distances from the solar system 1988 - Pluto's atmosphere discovered by the gravitational influence of the giant planets. The Earth's, Pluto's low gravity (about 6%of Earth's) causes 1992 - Nitrogen and carbon monoxide on Pluto's the atmosphere to be much more extended in altitude surface discovered than our planet's. Because Pluto's orbit is so elliptical, Fast Facts 1 1994 - First Hubble Space Telescope maps of Pluto Pluto grows much colder during the part of each orbit 2010 - Predicted atmospheric collapse when it is far from the Sun. As a result, Pluto's atmo- Namesake Roman God of the Underworld sphere is thought to persist only for the part of each orbit Average Distance from the Sun: 6 Billion Kilometers when Pluto is closer to the Sun, as it is now. Orbit Period 248 Years In 1978, American astronomers James Christy and Equatorial Diameter 2,400 Kilometers About the Image Robert Harrington discovered that Pluto has a satellite Atmosphere (Main Constituents) Nitrogen, This artist's conception of the PlutKharon binary planet (moon), which they named Charon. Charon, which is Carbon Monoxide, Methane was conceived and executed by Pat Rawlings of Science almost half the size of Pluto, orbits the planet every 6.4 Inclination of Orbit to Ecliptic 17.2" Applications International Corporation. Pluto is represented days, at an altitude of about 18,300 kilometers. Given in the background; Charon is in theforeground. The drawing Eccentricity of Orbit 0.25 the rough similarity of Pluto's size to Charon's, most depicts Pluto's true color, bright polar cap, tenuous atmo- planetary scientistsrefer to PlutoChamn as a double, or Rotation Period 6.387 Days sphere, and dark equatorial band. Notice how much brighter binary, planet. Charon's surface differs from Pluto's; it Inclination of Axis -120" Pluto's surface is than Charon's. The craters and other geo- is covered with dirty water ice and doesn't reflect as Moon Charon logical fsatures depicted are based on educated guesses about much light as Pluto's surface. Also, Charon's surface is Charon's Diameter 1,210 Kilometers the kinds offeaturesa flyby specraft might detect. uo!)e~)s!u!u~pvaxdg pue sagneuo~avleuo!geN I (lasul) e~dsegpue uooyy ~J!MepI :sp!oAalsV ------.- . ------
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The Galileo spacecraft, launched on October 18, has a moon. This tiny natural satellite, named Dactyl, has taught us much about the solar system. With 1989, has its primary mission reaching Jupiter's is about 1.2 x 1.4 x 1.6 kilometers. It orbits Ida at a advances in telescopic instrumentation in the last 5 system; however, its carefully designed trajectory distance of about 100 km from Ida's center. Like Ida years, scientists have recognized the wealth of path allowed the spacecraft to accomplish two and Gaspra, Dactyl is a heavily cratered body. The information that asteroids themselves may provide secondary missions: flying by two "minor planetsM- largest crater observed on Dactyl is about 80 meters about the solar system's origin and evolution. Gaspra and Ida--and sending back to Earth our first- across. Remarkably, Dactyl appears to be composed NASA's Near Earth Asteioid Rendezvous ever, close-up view of asteroids. of different materials than Ida. (NEAR) mission, scheduled to launch in February On October 29, 199 1, Galileo passed within Ida, like Gaspra, is an S-type asteroid, meaning 1996, will swing by Earth before reaching its main 1,600 kilometers of asteroid 95 1* Gaspra and, with that it is a reddish object composed of a mixture of the target-asteroid 433 Eros-in Januaryl999. Dur- incredible navigational accuracy, took pictures of it- minerals pyroxene, olivine, and iron. Approximately ing its 1-year rendezvous period, NEAR will address pictures that reveal an irregular planetary body one-sixth of all known asteroids fall within the S-type such questions as: "Is Ems related to a known riddled with craters and fractures. To date, over 600 category. Gaspra and Ida like other S-class asteroids meteorite type?" "Is Eros related to comets?" (Some craters have been identified on the asteroid, the are the parent bodies of some types of basaltic meteorites. scientists believe near-Earth asteroids are extinct or longest measuring about 1.5 kilometers across. The Asteroids have long be& recognized as the dormant comets) and "Is there evidence that Eros is a type of cracks seen-some more than 9Gmeters source of most meteorites. Our study of meteorites fragment of a larger body?" long-are similar to ones seen before only on the Martian moon Phobos. Some planetary scientists Fast Facts Significant uates theorize that about 4 billion years ago, Gaspra 951 Gaspra 243 Ida I 1801 Piazzi discovered fust asteroid,named 1 Ceres probably measured about 97 kilometers across. But, Distance from Sun after years of catastrophic collisions with other 1 1884 Palisa discovered asteroid 243 Ida (At Perihelion) (A.U.) 1.82 L. IL) 1898 Witt discovered asteroid 433 Eros planetary objects, the asteroid now measures a mere Period of Revolution 3.28 Years 4.84 Years 19 X 12 X 1 1 kilometers. This history may not be Length 19 lan 52 km 1916 Neujmin discovered asteroid 95 1 Gaspra unusual for asteroids like Gaspra, many of which are Inclination of Orbit 1991 Galileo encountered asteroid 95 1 Gaspra believed to have accreted into relatively substantial 1 to Ecliptic 1 1993 Galileo encountered asteroid 243 Ida minor planets during the formation of the solar Eccentricity of Orbit 1994 Dactyl discovered on Galileo images data system, only to be broken down in collisions over the Rotational Period 1 ensuing billions of years. (Hours: Minutes) 7:03 4:38 1996 NEAR mission will launch On August 28,1993, Galileo approached another Absolute Magnitude 12.9 11.05 1999 NEAR will encounter asteroid 433 Eros asteroid-Ida. This 52-kilometer-long asteroid is Asteroid Type S S more than twice as large as Gaspra. The images Galileo sent back reveal that numerous craters- References many larger than those observed on Gaspra-pepper About the I 1. Galileo Fact Sheet, NASA Headauarters, Washington the surface of the asteroid. The extensive craters Asteroid 243 Ida appears here with its moon, Dactyl DC. 3/92. (to the right). This i~ taken by Galilee in Augwt seem to dispel the once-believed theories that Ida's 2. Our Solor System, a Geologic Snapshot, NP-157, 1993, provides conclusive evidence that natural NASA Headquarters, Washington, DC. 5/92. surface is geologically youthful. The sharp images of satellites of asteroids exist. The asteroid 951 Gaspra 3. oursolor sysre,,,at a ~h~,Infomation summaries, Ida also dispel a popular belief that Ida is a double (inset)image is a mosaic of two images taken by PMS 010-A, Jet Propulsion Laboratory, Pasadena, CA. Galileofrom a range of 5,300 krn some 10 minutes body. Though Ida is not a double body in the sense 6/91. that astronomers had thought, Galileo found that it before closest approach, on October 29, 1991. Images are not to the same scale. These asteroids are located _,- --- IT*P-,-. *~nmnbavsigrrsdtorn~d(c&%l)~ihe~&~h~~ds belt between Mars and Jupiter. ------orbit wrs culloglm~. HqL-417 3/95 NASA Recn~lrpnc fnr Ed1 ~~+l+nre
For more information on NASA education programs Regional Teacher Resource Centers (RTRCs)I offer more for the classroom, teachers may contact the following: educators access to NASA educational materials. NASA has formed partnerships with universities, museums, and other NASA's Central Operation of Resources for educational institutions to serve as RTRCs in many states. Educators (CORE) was established for the national Teachers may preview, copy, or receive NASA materials at and international distribution of NASA-produced these sites. A complete list of RTRCs is available through educational materials in audiovisual format. CORE. Educators can obtain a catalogue of these materials and an order form by written request, on school NASA Spacelinkisan electronic informationsystem designed letterhead to: to providecurrent educational information toteachers, faculty, NASA CORE and students. Spacelink offers a wide range of computertext Loraln County Jo~ntVocat~onal School 15181 Roule 58 Soulh files, software, and graphics related to the space program. Oberlln. OH 44074 PHONE (216) 774-1051. Ext 293 or 294 The system may be accessed by computerthough direct-dial Teacher Resource Center Network modem or the Internet. To make additional information available to the Modem ltne (205) 895-0028 Term~nalemulat~on VT-100 requlred education community, the NASA Education Division Data format 8-N-1 has created the NASA Teacher Resource Center Telnet spacel~nkmsfc nasa gov (TRC) network. TRCs contain a wealth of information Spacelink fully supports the following lnternet services: World Wlde Web http ilspacel~nkmsfc nasa.gov for educators: publications, reference books, slide Gopher spaceltnk rnsfc nasa gov sets, audio cassettes, videotapes, telelecture Anonymous FTP spacel~nkmsfc nasa gov lnternet TCPilP address. 1921498961 programs, computer programs, lesson plans, and teacher guides with activities. Contact the TRC in For more information, contact: Spacelink Administrator, your region (see the listing below) for details on the Education ProgramsOffice, Mail CodeCL01, NASA Marshall services they provide: Space Flight Center, Huntsville, AL 35812-0001. AK, AZ, CA, HI, ID. MT, NV. OR. AL. AR, IA, LA, MO, JN Voice phone: (205) 961 -1225 UT, WA. WY U S Space and Rocket Center NASA Teacher Resource Center NASA Teacher Resource Center for E-mail: comments8spacelink.msfc.nasa.gov Mall Stop T12-A NASA Marshall Space Flight Center NASA Ames Research Center P 0 Box 07001 5 Moffetl F~eld.CA 94035-1000 Huntsv~lle.AL 35807-701 5 NASA Educational Satellite Videoconferences PHONE (415) 604-3574 PHONE (205) 544-5812 The Education SatelliteVideoconference SeriesforTeachers
CT, DE. DC. ME. MD. MA. NH, MS is offered as an in-service education program for educators NJ. NY, PA, RI, VT NASA Teacher Resource Center through the school year. The content of each program varies, NASA Teacher Resource Laboratory Bu~ld~ng1200 Mall Code 130 3 NASA John C. Stennis Space Center but includes aeronautics or space science topics of interest NASA Goddard Space Flight Center Stennls Space Center. MS 39529-6000 to elementary and secondary teachers. NASA program Greenbelt. MD 20771 -0001 PHONE. (601) 688-3338 PHONE (301) 286-8570 managers, scientists, astronauts, and education specialists Serves rnqulrres related to space and are featured presenters. The videoconference schedule is CO. KS. NE. NM, ND, OK, SD. TX planetary exploratron NASA Teacher Resource Room NASA Teacher Resource Center available on NASA Spacelink. Mall Code AP2 Mall Ston CS-530 NASA Johnson Space Center NASA Jet Propulsion Laboratory 2101 NASA Road One 4800 Oak Grove Dr~ve The videoconference series is free to registered educational Houston, TX 77058-3696 Pasadena. CA 91 109-8099 institutions. To participate, the institution must have a PHONE (713) 483-8696 PHONE (818) 354-6916 C-band satellite receiving system, teacher release time, and FL. GA, PR, VI CA crhes near the facrhly an optional long distance telephone line for interaction. NASA Educators Resource Laboratory Publ~cAffa~rs Office (Trl 42) Mall Code ERL NASA Teacher Resource Center Arrangements may also be made to receive the satellite NASA Kennedy Space Center NASA Dryden Flight Research Facility signal through the local cable television system. The programs Kennedy Space Center, FL 32899-M)01 Edwards. CA 93523-0273 PHONE (407) 867-4090 PHONE (805) 258-3456 may be videotaped and copied for later use.
KY. NC. SC. VA. WV VA and MD's Eastern Shores Vlrglnta Air and Space Museum NASA Teacher Resource Lab For more information, contact: Videoconference Producer, NASA Teacher Resource Center for Educat~onComplex -V~s~torCenter NASATeaching From Space Program, 308ACITD, Oklahoma NASA Langley Research Center Bu~ld~ngJ-17 600 Settler's Land~ngRoad NASA Wallops Flight Facility State University, Stillwater, OK 74078-8089 Hampton. VA 23669-4033 Wallops Island, VA 23337-5099 E-mail: [email protected] PHONE (804) 727-0900 x 757 PHONE. (804) 824-2297i2298
IL, IN. MI. MN. OH. WI How to Access NASA Education Materials and Services, NASA Teacher Resource Center Mall Slop 8-1 PED-329 April 1995. This brochure serves as a guide to NASA Lewis Research Center accessing a variety of NASA materials and services for 21000 Brookpark Road Cleveland. OH 44135-3191 Copies are available through the TRC network. PHONE (216) 433-2017 August 1995 -. .,J following listing of Internet addresses will provide users with robust links to earth and space science educational materials throughout the WWW. NASA resources begins with sites that cover a range of topics and becomes increasingly science specific.
NASA Resources Other Earth and Space Science Resources
NASA SpaceLink American Geophysical Union http://spaceIink.msfc.nasa.gov http://earth.agu.org/kosmos/homepage/html
NASA Home Page Arizona Mars K-12 Educational Supplement http://www.nasa.gov/ and Guide http://esther.la.asu.edu/cgi-bin/imagemap/ NASA Goddard Space Flight Center tes_horne?l44,327 Space Science Education Home Page http://www.gsfc.nasa.gov/education/ Astronomical Society of the Pacific education-home.html http://www.physics.sfsu.edu/asp/asp.html
NASA Mission To Planet Earth Home Page Earth System Science Education Program http://www. hq.nasa.gov/office/mtpe Universities Space Research Association http://www.usra.edu/esse/ NASA Jet Propulsion Laboratory Educational~Resources.html Learning Link http://learn.jpl.nasa.gov The Planetary Society http://planetary.org/tps/ Remote Sensing Public Access Center http://www. rspac.iw.nasa.gov Space Telescope Science Institute (STScl) Hubble Space Telescope's Greatest Hits 1990- Public Access to NASA's Planetary Data 1995 Picture Gallery http://stardust.jpl.nasa.gov/public http~/www.stsci.edu/public.html
Lunar and Planetary Institute Space Telescope Science Institute Exploration http://cass.jsc.nasa.gov/lpi. html in Education (EXlnED) Picture Books http://stsci.edu/exined-htmllexined-home.html Astronomy On-line: Ask Dr. Sue http://dlt.gsfc.nasa.gov/Ask Telescopes In Education http://www.mtwilson.edu/tie.html NASNJPL Imaging Radar Home Page http://southport.jpl.nasa.gov YAHOO http://www.yahoo.com/Education Global Quest: The lnternet in the Classroom http://quest.arc.nasa.gov
August 1995 SA Strongly Agree Educators and scientists at the National Aeronautics and Space Administration - A Agree would appreciate your taking a few minutes to respond to the statements and - D Disagree questions below. Please return by mail. - SD - Strongly Disagree Solar System Lithograph Set SA A D SD 1. The lithograph set is easily integrated into the curriculum. - SA A D SD 2. It is helpful to me to have a complete set of planetary images. - SA A D SD 3. The information on the back of the lithographs is both informative and educational. - 4. a. What features of the lithographs are particularly helpful in your teaching?
-- b. What changes would make the set more effective for you?
5. 1 teach grade. Subjects
6. 1 used the guide with (number of ) students.
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