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Above: the Greek sign for Jupiter
Jupiter (a.k.a. Jove; Greek Zeus) was the King of the Gods, the ruler of Olympus and the patron of the Roman state. Zeus was the son of Cronus (Saturn).
Jupiter is the fourth brightest object in the sky (after the Sun, the Moon and Venus; at some times Mars is also brighter). It has been known since prehistoric times. Galileo's discovery, in 1610, of Jupiter's four large moons Io, Europa, Ganymede and Callisto (now known as the Galilean moons) was the first discovery of a center of motion not apparently centered on the Earth. It was a major point in favor of Copernicus's heliocentric theory of the motions of the planets; Galileo's outspoken support of the Copernican theory got him arrested by the Inquisition. He was forced to recant his beliefs and was imprisoned for the rest of his life.
Most of the mass in the Solar system is found in the outer solar system. Jupiter alone has more mass than all of the other planets combined. The chemistry of the outer solar system is also very different. When the planets and the Sun were forming, the parts of the solar nebula farther from the Sun were cooler. This allowed water to condense, otherwise these materials remained as gas (and eventually dissipated) in the solar system.
Because of this, the formation stages of the outer planets had a greater mass of solid material to begin with. This meant that the core bodies for the giant planets had more gravity to the gases hydrogen and helium, which were abundant in the solar nebula. Therefore, the outer planets were able to grow significantly bigger than those that were closer to the Sun.
Most of the oxygen chemically combined with hydrogen to make H2O, and was then unavailable to form oxidized compounds with other elements. So, the compounds detected in the atmosphere of Jupiter and the other giant planets are hydrogen-based gases such as methane and ammonia, and more hydrocarbons such as ethane and acetylene.
Our knowledge of the interior of Jupiter was gathered indirectly. (The data from Galileo's atmospheric probe goes down only about 150 km the cloud tops.)
Jupiter probably has a core of rocky material that is something like 10 to 15 times the mass of the Earth. Above the core is the main part of the planet in the form of liquid metallic hydrogen. This exotic element is possible only at pressures exceeding 4 million bars, as is the interior of Jupiter (and Saturn). Liquid metallic hydrogen is composed of ionized protons and (like the interior of the Sun but at a far lower temperature). At the temperature of Jupiter's interior, the hydrogen is a liquid not a gas. It is an electrical conductor and the source of Jupiter's magnetic field. This layer also probably contains some helium and traces of "ices".
The outermost layer is composed of hydrogen and helium which is liquid towards the interior and a gas further out. The atmosphere that we can see through a telescope is just the very top of this deep layer. Water, carbon dioxide, methane and other simple molecules are also present in trace amounts.
Three distinct layers of clouds are believed to exist consisting of ammonia ice, ammonium hydrosulfide and a mixture of ice and water. However, the Galileo probe shows only small indications of clouds (one instrument seems to have detected the topmost layer while another may have seen the second). But the probe's entry point was unusual -- Earth-based telescopic observations and more recent observations by the Galileo orbiter suggest that the probe entry site may well have been one of the warmest and least cloudy areas on Jupiter at that time.
Data from the Galileo probe also indicate that there is much less water than expected. The expectation was that Jupiter's atmosphere would contain about twice the amount of oxygen (combined with the abundant hydrogen to make water) as the Sun. But it now appears that the actual amount is much less than the Sun's. Also surprising was the high temperature and density of the upper parts of the atmosphere.
Jupiter and the other gas planets have high velocity winds which occur only in certain sections of bands of latitude. The winds blow in opposite directions in adjacent bands. Slight chemical and temperature differences between these bands make the colored bands that you see on Jupiter. The light colored bands are called zones, the dark ones belts. The bands have been known for awhile on Jupiter, but the complex vortexes in the regions between the bands were first seen by Voyager. The data from the Galileo probe said that these winds move even faster than thougt (more than 400 mph) and extend down as far as the probe was able to see. They may extend down thousands of kilometers into the interior. Jupiter's atmosphere was also found to be quite turbulent. This shows that Jupiter's winds occur because of its internal heat rather than from solar radiation as on Earth.
The colors seen in Jupiter's clouds are probably the result of small chemical reactions of the trace elements in Jupiter's atmosphere, maybe involving sulfur whose compounds take on a wide variety of colors, but the exact reasons are still unknown.
The colors are in direct correslation with their altitude: blue lowest, followed by browns and whites, with reds highest. Sometimes we see the lower layers through holes in the upper ones.
 The Great Red Spot (GRS) (right) has been seen by Earthly observers for more than 300 years (its discovery is usually credited to Cassini, or Robert Hooke in the 17th century). The GRS is about 12,000 by 25,000 km, big enough to hold two Earths. Other smaller but similar spots have been known for decades. Infrared observations and the direction of its rotation indicate that the GRS is a high-pressure region whose cloud tops are significantly higher and colder than the surrounding regions. Similar structures have been seen on Saturn and Neptune. It is not known how these structures can last for so long.
Jupiter gives off more energy than it receives from the Sun! The interior of Jupiter is hot: the core is probably around 20,000 K. The heat is generated by the Kelvin-Helmholtz mechanism, the slow gravitational compression of the planet. (Jupiter does NOT produce energy by nuclear fusion as in the Sun It is way too small and its interior is too cool to start a nuclear reaction.) This interior heat probably causes convection deep within Jupiter's liquid layers and is probably responsible for the complex motions we see in the cloud tops. Saturn and Neptune are similar to Jupiter in this aspect, but oddly, Uranus is not.
Jupiter is just about as large as a gas planet can be. If more material were to be added, it would be compressed by gravity so that the overall radius would increase only slightly. Very, very interesting! A star can be larger only because of its internal (nuclear) heat source. Jupiter would have to be at least 80 times more massive to become a star.
Jupiter has a huge magnetic field, much stronger and bigger than Earth's. Its magnetosphere extends more than 650 million km (past the orbit of Saturn!). Jupiter's magnetosphere is not spherical -- it extends "only" a few million kilometers in the direction toward the Sun. Jupiter's moons therefore lie within its magnetosphere, a fact which may partially explain some of the activity on its moon, Io. Unfortunately for future space travelers and of much concern to the designers of the Voyager and Galileo spacecraft, the environment near Jupiter contains large amounts of energetic particles trapped by Jupiter's magnetic field. This "radiation" is similar to, but much more intense than, that found within Earth's Van Allen belts. It would be fatal to an unprotected human being. The Galileo atmospheric probe discovered a new intense radiation belt between Jupiter's ring and the uppermost atmospheric layers. This new belt is approximately 10 times as strong as Earth's Van Allen radiation belts. More surprisingly, this new belt was also found to contain high energy helium ions of unknown origin.
 Jupiter has rings (right) like Saturn's, but much fainter and smaller. They were totally unexpected and were only discovered when two of the Voyager 1 scientists insisted that after traveling 1 billion km it was at least worth a quick look to see if any rings might be present. Everyone else thought that the chance of finding anything was nada, but there they were!! They have since been imaged in infrared images made by ground-based telescopes and by Galileo.
Unlike Saturn's, Jupiter's rings are dark (albedo about 0.05). They're probably composed of very small grains of rocky material. Unlike Saturn's rings, they seem to contain no ice.
Particles in Jupiter's rings probably don't stay there for long due to atmospheric and magnetic drag. The Galileo spacecraft discovered that the rings are continuously being renewed by dust formed by micrometeor impacts on the four inner moons, which are very energetic because of Jupiter's large gravitational field. The inner halo ring is broadened by interactions with Jupiter's magnetic field.
In July 1994, Comet Shoemaker-Levy 9 collided with Jupiter with spectacular results. The effects were clearly visible even with amateur telescopes. The debris from the collision was visible for about a year after with HST.
When it is in the nighttime, Jupiter is often the brightest "star" in the sky (it is second only to Venus, which isn't that often visible in a dark sky). The four Galilean moons are easily visible with binoculars; a few bands and the Great Red Spot can be seen with a small telescope. There are several Web sites that show the current position of Jupiter (and the other planets) in the sky. More detailed and customized charts can be created with a planetarium program such as Starry Night.
Jupiter has 16 known satellites, the four large Galilean moons and 12 small ones.
- Jupiter is very gradually slowing down due to the tidal drag produced by the Galilean satellites. Also, the same tidal forces are changing the orbits of the moons, very slowly forcing them further away from Jupiter.
- Io, Europa and Ganymede are "locked" together by tidal forces into a 1:2:4 orbital resonance and their orbits evolve together. In a few hundred million years, Callisto will be locked in too, orbiting at exactly twice the period of Ganymede and eight times the period of Io.
- Jupiter's satellites are named for other figures in the life of Zeus (mostly his lovers).
Satellite
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Distance(000 km)
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Radius(km)
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Mass(kg)
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Discoverer
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Date
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Metis
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128
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20
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9.56e16
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Synnott
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1979
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Adrastea
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129
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10
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1.91e16
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Jewitt
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1979
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Amalthea
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181
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98
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7.17e18
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Barnard
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1892
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Thebe
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222
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50
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7.77e17
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Synnott
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1979
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Io
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422
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1815
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8.94e22
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Galileo
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1610
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Europa
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671
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1569
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4.80e22
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Galileo
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1610
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Ganymede
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1070
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2631
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1.48e23
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Galileo
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1610
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Callisto
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1883
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2400
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1.08e23
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Galileo
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1610
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Leda
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11094
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8
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5.68e15
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Kowal
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1974
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Himalia
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11480
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93
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9.56e18
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Perrine
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1904
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Lysithea
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11720
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18
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7.77e16
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Nicholson
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1938
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Elara
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11737
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38
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7.77e17
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Perrine
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1905
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Ananke
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21200
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15
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3.82e16
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Nicholson
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1951
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Carme
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22600
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20
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9.56e16
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Nicholson
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1938
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Pasiphae
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23500
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25
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1.91e17
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Melotte
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1908
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Sinope
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23700
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18
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7.77e16
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Nicholson
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1914
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Values for the smaller moons are approximate.
Jupiter's Rings
Ring
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Distance(km)
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Width
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Mass
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Halo
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92000
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30500
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?
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Main
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122500
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6440
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1e13
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Gossamer
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128940
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100000
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?
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Here you will find all the stats and facts for Jupiter. This includes everything from the escape velocity needed to leave its surface to surface temperatures! All these figures will be compared with Earth...
Discoverer: Unknown
Discovery Date: Prehistoric
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Jupiter
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Earth
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Ratio (Jupiter/Earth)
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| Mass (1024 kg) |
1,898.6 |
5.9736 |
317.83 |
| GM (x 106 km3/s2) |
126.686 |
0.3986 |
317.8 |
| Volume (1012 km3) |
143,128 |
108.321 |
1321.33 |
| Equatorial radius (km) |
71,492 |
6,378.1 |
11.209 |
| Polar radius (km) |
66,854 |
6,356.8 |
10.517 |
| Volumetric mean radius (km) |
69,911 |
6,371.0 |
10.973 |
| Mean density (kg/m3) |
1,326 |
5,515 |
0.240 |
| Surface gravity (eq.) (m/s2) |
23.12 |
9.78 |
2.364 |
| Escape velocity (km/s) |
59.5 |
11.19 |
5.32 |
| Ellipticity (Flattening) |
0.06487 |
0.00335 |
19.36 |
| Moment of inertia (I/MR2) |
0.254 |
0.3308 |
0.768 |
| Visual magnitude V(1,0) |
-9.40 |
-3.86 |
-
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| Bond albedo |
0.343 |
0.306 |
1.12 |
| Visual geometric albedo |
0.52 |
0.367 |
1.42 |
| Solar irradiance (W/m2) |
50.50 |
1367.6 |
0.037 |
| Black-body temperature (K) |
110.0 |
254.3 |
0.433 |
| J2 (x 10-6) |
14,736 |
1082.63 |
13.611 |
| Semimajor axis (106 km) |
778.57 |
149.60 |
5.204 |
| Sidereal orbit period (days) |
4,332.589 |
365.256 |
11.862 |
| Tropical orbit period (days) |
4,330.595 |
365.242 |
11.857 |
| Perihelion (106 km) |
740.52 |
147.09 |
5.034 |
| Aphelion (106 km) |
816.62 |
152.10 |
5.369 |
| Synodic period (days) |
398.88 |
-
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-
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| Mean orbital velocity (km/s) |
13.07 |
29.78 |
0.439 |
| Max. orbital velocity (km/s) |
13.72 |
30.29 |
0.453 |
| Min. orbital velocity (km/s) |
12.44 |
29.29 |
0.425 |
| Orbit inclination (deg) |
1.304 |
0.000 |
-
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| Orbit eccentricity |
0.0489 |
0.0167 |
2.928 |
| Sidereal rotation period (hrs) |
9.9250 |
23.9345 |
0.415 |
| Length of day (hrs) |
9.9259 |
24.0000 |
0.414 |
| Obliquity to orbit (deg) |
3.13 |
23.45 |
0.133 |
| Min. distance from Earth (106 km) |
588.5 |
| Max. distance from Earth (106 km) |
968.1 |
**Don't understand these measurements? Click here to get help with the definitions and notes**
Atmospheric Composition
Molecular hydrogen (H2) - 89.8% (2.0%)
Helium (He) - 10.2% (2.0%)
Trace Amounts of (ppm):
Methane (CH4) - 3000 (1000)
Ammonia (NH3) - 260 (40)
Hydrogen Deuteride (HD) - 28 (10)
Ethane (C2H6) - 5.8 (1.5)
Water (H2O) - ~4 (varies with pressure)
- Galileo's atmospheric probe provides our first direct measurement of Jupiter's atmosphere, our first real data about the chemistry of a gas planet. The initial data indicate a major new mystery -- why is there so little water in Jupiter's atmosphere? There is a building concensus that the probe encountered an unusually dry area but more details are needed.
- Just how deep into the interior do the zonal winds extend? What mechanism drives them?
- Why is the GRS so persistent? There are actually several theoretical models that seem to work. We need more data to decide between them.
- How can we get more direct information about the interior? Liquid metallic hydrogen has been produced in a lab at Lawrence Livermore National Laboratory but much about its properties is still unknown.
- Why are Jupiter's rings so dark while Saturn's are so bright?
All nine photos below are of great quality and very large!! So download time will be slow, but well worth it...
Click on any image to view it full size!
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Jupiter
