Size 2 Jupiter Is the Largest Planet in the Solar System, Measuring 88,850 Miles in Diameter

Jupiter 1

 Name – The planet Jupiter is named after the king of the gods in Roman mythology.  Size 2 – Jupiter is the largest planet in the solar system, measuring 88,850 miles in diameter.  Location – Jupiter is the fifth planet from the Sun, with an average distance of approximately 484 million miles.  Orbital period – 11.86 years.  Rotational period – 9.83 hours.  Number of Satellites – 67 known moons.

Atmosphere

 Composition – Jupiter’s atmosphere is primarily composed of hydrogen (88-92%) and helium (8-12%).  Trace Constituents – Jupiter’s atmosphere also contains trace amounts of methane, ammonia, hydrogen deuteride, ethane, water, carbon, hydrogen sulfide, neon, oxygen, phosphine, sulfur, and silicon-based compounds. Traces of hydrocarbons (hydrogen-carbon compounds), such as acetylene and benzene have also been found. The Sun’s ultraviolet radiation breaks down the methane in Jupiter’s atmosphere to form these hydrocarbons. This process, known as photochemistry, is also responsible for the formation of the Earth’s ozone layer, the sulfuric acid clouds of Venus, and the trace constituents within the atmospheres of Saturn, Uranus, and Neptune. In addition, lightning (up to a thousand times more powerful than lightning on Earth) observed within the clouds of Jupiter may contribute to the formation of hydrocarbons.  Hydrogen-Helium Rich Atmosphere – Because of Jupiter’s strong gravitational force and the cold temperatures (-150º F) associated with the planet’s distance from the Sun, the retention of a hydrogen-helium rich atmosphere is possible. (The atmospheres of Saturn, Uranus and Neptune are also hydrogen-helium rich for the same reasons.)

1  Circulation – The structure of Jupiter’s atmosphere is related to its circulation. Jupiter exhibits a constantly shifting pattern of clouds, but its overall appearance is characterized by a fairly constant pattern of alternating bright and dark bands 3. The formation and stability of these bands are due to the planet’s high rotation rate and lack of a solid (obstructive) surface. (These reasons also apply to bands found within the atmospheres of Saturn, Uranus, and Neptune.) The variation in their brightness is associated with the boundaries of convection cells. The bright bands, referred to as zones, are associated with the upwelling portions of the convection cells, while the dark bands, referred to as belts, are associated with the downwelling portions 4.

 Colored Clouds 5 – Jupiter’s atmosphere consists of layers of clouds of varying color. Temperature, pressure, gas composition and abundances determine the characteristics of these clouds. Moreover, many of the color differences may be the result of observing to varying depths. Specifically, clouds composed of ammonia-ice crystals characterize the upper, colder levels of Jupiter’s atmosphere. At deeper, warmer levels, sulfur compounds may be responsible for the yellow, beige and dark brown colored clouds.  Brown Ovals 6 – Brown ovals observed in Jupiter’s atmosphere could be openings in the upper cloud deck where warmer cloud levels may exist. Features of this type have an average lifetime of one to two years.

 Storms 7 – The most striking feature of Jupiter’s atmosphere is the Great Red Spot. First observed over 350 years ago, it appears to be a hurricane-like storm, with wind speeds up to 400 miles/hour 8. The Great Red Spot most likely originated from an eddy between counter-flowing eastward and westward winds, called zonal jets 9. Its dimensions are about 16,000 by 9,000 miles, making it large enough to accommodate two planets the size of our Earth side-by-side 10. The chemicals responsible for the reddish color of the Great Red Spot are unknown. However, red phosphorous, complex organic compounds, and sulfur compound have been considered. In 1938, three smaller storms referred to as white ovals 11 were discovered within Jupiter’s atmosphere. By 2000, they merged to form a single storm (Earth-size), increasing in intensity, and changing color from white to red. Though formally named Oval BA, it has been nicknamed “Red Spot Jr.” 12.

 Longevity – Why are storms on Jupiter so long-lived? On Earth, powerful storms such as hurricanes dissipate when they traverse land. Without the condensation of water vapor (condensation releases energy) that comes from the oceans, these storms lose their energy. On Jupiter, there are no continents, and once these storms grow large enough to overcome the effects of encounters with smaller systems, they can persist for long periods of time. Moreover, internal heat (discussed later) may be a source of power for Jupiter’s atmospheric winds and storms.

2 Interior

 Model – Since Jupiter lacks a solid surface, seismic data cannot be obtained to reveal properties of the planet’s interior. However, it is possible to construct a plausible model of Jupiter’s interior from data derived from remote surveys. The distribution and state of matter inside of Jupiter can be determined from information such as density (1.31 g/cm3), mass, radius, rotation rate, heat balance, and atmospheric composition.

 Composition and Structure 13 – Jupiter’s interior has no well-defined boundaries. Instead, with increasing depth, there is fairly gradual transition of the materials that make up its interior. Although Jupiter is differentiated, these changes are primarily related to an increase of pressure and temperature.  Liquid Molecular Hydrogen – Below Jupiter’s atmosphere the pressure is high enough to cause molecular hydrogen gas to be liquefied, and therefore produce a layer referred to as liquid molecular hydrogen (H2).  Liquid Metallic Hydrogen – Eventually, with increasing depth, the pressure and temperature become high enough to cause electrons to break free of the hydrogen nuclei, thus forming ionized hydrogen (atoms missing electrons so that they have net positive charge). The liquid hydrogen then has the conductivity of metals, producing a layer referred to as liquid metallic hydrogen.  Magnetic Field – Jupiter has a strong magnetic field, with an intrinsic strength 19,000 times greater than the Earth. The origin of Jupiter’s magnetic field is the liquid metallic hydrogen layer. This layer has the necessary properties for the formation of a planetary magnetic field – metallic, liquid phase, and convective processes (a dynamo) generated by Jupiter’s high rotation rate.  Core – It is speculated that Jupiter’s core is 10 to 20 times the mass of the Earth, and mainly composed of silicate rock and ice. The rock may include some nickel- iron and the ice may be a mixture of water, ammonia and methane. Although, the temperature within the core is calculated to be about 50,000 F, the pressure (about 100 million bars) is so high that the core material remains in a solid state.

 Liquid Planets – Although Jupiter and the other Jovian planets are often referred to as the gas giants, in actuality they are mainly composed of material in a liquid state.

 Internal Energy – Jupiter radiates twice as much energy as it receives from the Sun. However, this energy is released as infrared radiation (heat energy), not visible light. The source of this energy is derived from the planet’s continuing contraction (referred to as the Kelvin-Helmholtz mechanism) from a protoplanetary phase. In other words, Jupiter’s mass is moving inward under the influence of gravity, and the resulting energy of motion (kinetic energy) is transformed into heat. This process results in the planet shrinking by about 2 cm each year.

3 Ring System

 Discovery and Observations – Although the ring system of Jupiter was discovered by the Voyager mission in 1979, data derived from the Pioneer mission in 1974 suggested the possibility of its existence. Jupiter’s rings can be seen by ground-based telescopes, but only barely. Because of their tenuous nature, most probe images of the rings were acquired by forward-scattering light (light redirected slightly by diffraction off its path from the Sun) rather than reflected light 14.

 Composition and Structure 15 – Jupiter’s ring system is mainly composed of dark silicate dust (about the size of cigarette smoke particles), and is divided into three components: main ring, halo, and gossamer ring.

 Origin – The origin of Jupiter’s ring system is the result of the ejection of dust from the surfaces of some of the planet’s minor moons by a combination of small impacts and the blasting by atomic particles of Jupiter’s magnetosphere. Because of the small size of the ring particles, they easily acquire a small electrical charge from interaction with Jupiter’s magnetosphere, and the mutual repulsive force of these charge particles lifts them out of the ring plane. As a result, dust is continuously swept away, but is replenished by new particles eroded from the small satellites.

 Galilean Satellites 16 – One of Galileo’s telescopic discoveries was the four major moons of Jupiter. They are known collectively as the Galilean satellites, in honor of their discoverer. In order of increasing distance from Jupiter, they are: Io, Europa, Ganymede, and Callisto 17. The Galilean satellites most likely originated from the coalescence of a disk of gas and dust (referred to a protosatellite nebula) surrounding Jupiter very early in its history. Their diameters range from about 1900 miles to nearly 3300 miles. Ganymede is not only the largest moon of Jupiter, but also the largest moon in the solar system, exceeding the size of Mercury. The density of the four moons decreases with distance from Jupiter. Specifically, Io’s density (3.53 g/cm3) is intermediate between rock and iron, whereas Callisto’s density (1.83 g/cm3) is intermediate between ice and rock. Evidence indicates that Callisto is partially differentiated. In contrast, the interiors of Io, Europa, and Ganymede appear to be differentiated. The current model is that these three moons experience tidal heating (discussed later) as a result of Jupiter’s gravitational field. Moreover, the nearer the moon is to Jupiter, the hotter the interior. In all but Callisto, this will have melted the interior ice, allowing rock and iron to sink to the interior and water to cover the surface. In Ganymede a thick and solid ice crust then formed. In warmer Europa a thinner more easily broken crust formed. In Io the heating is so extreme that all the rock has melted and all the water has long ago boiled out into space.

4  Io 18 – With over 400 active volcanoes, Io is the most volcanically active object in the solar system. No impact craters have been observed on the moon, indicating that the surface is very young (probably less than one million years old). Io is capable of erasing its craters as fast as they are formed. Unlike the Earth, Io’s main source of internal heat comes from tidal flexing rather than radioactive isotope decay. Because of Jupiter’s strong gravitation, Io has developed a large tidal bulge. In addition, gravitational interactions in the satellite system have made Io’s orbit eccentric, thus varying the distance between Jupiter and Io and thereby causing the height of the tidal bulge to fluctuate by about 300 feet. As Io orbits Jupiter, the bulge moves, flexes the crust, and heats Io's interior (like a paper clip bent rapidly back and forth), providing abundant molten material for the intense volcanic activity associated with the moon.  Color 19 – The surface of Io exhibits a variety of colors. The yellow, red, black, and green are most likely attributed to allotropes (elemental sulfur, which has the property of taking on many colored forms depending on its temperature and the way it is cooled from the liquid state) and sulfur compounds. The white areas on Io most likely originate from the ejected gas of plumes, which freezes when released into the cold of space and falls back onto Io’s surface as sulfur dioxide frost.  Plume Eruptions 20, 21 – The largest volcanic events on Io are the plume eruptions. Similar to geysers on Earth, plume eruptions spray about 100,000 tons of material each second, enough to alter the color of an area of thousands of square miles in a few weeks. Plume eruptions take place when lava flows encounter the thick deposits of frozen sulfur dioxide. They are similar to the explosive eruptions that sometimes occur when terrestrial lava flows meet bodies of ice or water. However, on Io, where the temperatures are lower and there is almost no atmosphere, the plumes can shoot up to tremendous heights (up to 300 miles).  Paterae 22 – Io’s surface is dotted with volcanic depressions known as paterae. Resembling terrestrial calderas, paterae generally have flat floors bounded by steep walls. However, they do not lie at the peak of volcanoes and are typically larger. The formation mechanism of paterae is unclear, but may relate to volcanic sills – layers of subsurface molten rock.  Lava Flows 23 – Lava flows represent another major volcanic feature on Io. Magma erupts onto the surface from vents on the floors of paterae or on the plains from fractures. Earth-based infrared studies and measurements from the Galileo spacecraft indicate that these flows are composed of basaltic lava.  Mountains 24 – Io has more than 100 mountains, some of which are taller than Mount Everest. Most of these mountains are tectonic structures, and form as the result of compressive stresses on the base of the lithosphere, which uplift and tilt chunks of Io’s crust. A handful of mountains on Io appear to have a volcanic origin, resembling small shield volcanoes.

5  Europa 25 – Europa’s surface is extremely smooth with few features exceeding a few hundred feet in height. It is the brightest of any of the Galilean satellites, composed of relatively pure water-ice. Moreover, there are very few craters on Europa; only three craters larger than about 3 miles in diameter have been observed. These characteristics suggest a continuing process that resurfaces the moon with fresh material below. Like Io, Europa is subjected to tidal heating, but because Europa is further from Jupiter than Io the tidal effect is less dramatic. Specifically, the effect of the tides induced by Jupiter heats the interior of Europa sufficiently to keep the surface soft. Therefore, no vertical relief features can survive for long on Europa's surface, explaining its smoothness.  Chaos Terrain 26 – Although Europa mainly consists of smooth terrain, a few percent of the moon’s surface has been subjected to geological deformation. Referred to as chaos terrain, these areas formed when the ice crust was broken into pieces (hundreds of feet to a few miles across), and then rotated or tilted as if they were icebergs floating in an ocean. However, these icebergs are not free-floating today, but embedded within younger ice.  Lineae 27 – Europa’s most striking surface features are a series of dark, reddish-brown streaks (possibly colored by sulfur compounds) crisscrossing the entire globe, called lineae (English: lines). Lineae may have been produced by a series of eruptions of warm ice as the Europa’s crust spread open to expose warmer layers beneath. The effect would have been similar to that seen in Earth’s oceanic ridges. Furthermore, studies of Voyager and Galileo images have revealed evidence of subduction on Europa’s surface, suggesting that, just as the lineae are analogous to ocean ridges of diverging plates, so these areas are analogous to converging plates. It has been proposed that heat from tidal flexing, which causes the ocean to remain liquid, also drives geological activity similar to plate tectonics.  Life? – Evidence suggests that there is a large ocean of liquid water below Europa’s ice crust 28. A global ocean and an internal heat source have made Europa a target of prime interest in the search for extraterrestrial life. Like life associated with hydrothermal vents on the Earth’s ocean floor, life on Europa would need to extract its energy from chemical reactions that take place from the heating of its interior. Further exploration of Europa will be necessary to answer this question. Specifically, missions that will include vehicles capable of melting through the ice crust to explore the subsurface liquid zone. (The idea has been raised that life may also exist in oceans under the surfaces of Ganymede and Callisto.)  Ganymede 29 – Ganymede has a combination of a dark terrain that probably dates back to the early history of the solar system, and a younger, brighter terrain (sometimes referred to as the bright grooved terrain) that once experienced extensive tectonic activity. In addition, Ganymede is the only satellite in the solar system known to possess a magnetosphere, likely created through convection within the liquid iron core.

6  Dark Terrain – Ganymede’s dark terrain is heavily cratered, suggesting a surface age about 4 billion years. The dark coloration is most likely the result of the accumulation of meteoritic dust, which covers a brighter, ice sub-layer. Evidence of this sub-layer is seen where impacts ejected fresh ice onto the surface 30.  Bright Grooved Terrain – The forces that caused the strong stresses in the Ganymede’s ice crust necessary to initiate the tectonic activity, and thus the formation of the bright grooved terrain, may be connected to the tidal heating in the past. Specifically, the tidal heating “flexed” the ice crust causing the development of cracks and horst and graben faulting – a horst represents a block of crust pushed upward by the faulting, and a graben is a block of crust that has dropped due to the faulting. The term “sulcus”, meaning a groove or burrow, is often used to describe the grooved features. For example, Uruk Sulcus 31.  Palimpsest 32 – A palimpsest is an ancient crater whose features have disappeared due to “relaxation” of the icy surface or subsequent cryovolcanic outpourings, leaving a circular feature, perhaps with a “ghost” of a rim.  Callisto 33 – Callisto has the most heavily cratered, and hence the oldest surface of the Galilean satellites (very little to no tectonic activity has occurred on this moon). Like Ganymede’s dark terrain, Callisto’s surface overall is dark due to the contamination of the icy surface by meteoritic material. However, bright spots are widespread, formed by young impacts ejecting fresh ice onto the surface.  Craters – Over most of Callisto’s surface, craters are nearly as densely packed as those in the lunar highlands. These craters were most likely formed early in the moon’s history during a time of higher cratering rates. Like Ganymede, Callisto has palimpsests.  Multi-ringed Structures 34 – Multi-ring structures probably originated as a result of a post-impact concentric fracturing of the lithosphere lying on a layer of soft or liquid material, possibly an ocean. Also, these impacts blasted deep into Callisto’s interior, ejecting fresh ice onto the surface and causing the central portions of these structures to appear brighter than the surrounding regions. The largest of multi-ringed structure is Valhalla, spanning a length equivalent to the contiguous United States.

 Minor Moons 35 – Jupiter has 63 minor satellites, which range in diameter from less than 10 miles to about 170 miles. They are irregularly shaped objects, with dark surfaces similar to primitive asteroids found within the main asteroid belt. In fact, with the exception of four of these moons forming with Jupiter, the rest may have been initially asteroids, captured by Jupiter’s strong gravity.