Steven Dutch, Professor Emeritus, Natural and Applied Sciences,University of Wisconsin - Green Bay
- Fifth planet from the Sun
- Average distance from Sun = 484 million miles.
- 5.2 times the average distance of Earth
- 3.4 times the average distance from Mars
- Perihelion distance 460 million miles.
- Aphelion distance 508 million miles.
- Takes 11.86 years or 4330 days to revolve around the Sun.
- Jupiter rotates on its axis in slightly under 10 hours.
Jupiter is Huge
- Equatorial diameter = 89,000 miles, more than 11 times the Earth's diameter.
- The visible surface of Jupiter has about 120 times the area of the Earth.
- Jupiter is 318 times as massive as the Earth and 2-1/2 times as massive as all the otherplanets in the Solar System put together.
- Jupiter's volume is more than 1300 times that of the Earth.
- Jupiter is still only 1/10 the diameter and 1/1000 the mass of the Sun.
Structure of Jupiter
- Its average density is only about 1.3.
- It probably has no solid surface, but rather a very deep atmosphere grading downward intoliquid, then solid, hydrogen, possibly with a small rocky core.
- Jupiter's makeup is much like the Sun: 90% hydrogen and about 10% helium, with minoramounts of methane (CH4), ammonia (NH3), water, carbon monoxide, ethane (C2H6) and otherthings.
- Jupiter is entirely covered with cloud bands. The clouds are made of water ice, ammonia ice,ammonium hydrosulfide (HN4SH) and hydrocarbons.
- Large storm systems persist on Jupiter for long periods. The Great Red Spot, twice the sizeof Earth, is a large high-pressure system that has persisted for at least 300 years.
- Jupiter has an immense magnetic field hundreds of times stronger than that of the earth. Thisfield traps and accelerates particles from the solar wind and produces enormous radiation beltsand electrical currents.
- The radiation belts are so strong that the inner 3 Galilean satellites suffer radiationbombardments that would be lethal to humans in a short time.
- All the spacecraft which have passed Jupiter absorbed hundreds of times the lethal radiationdosage in just the few hours they were near Jupiter.
- Jupiter emits twice as much energy as it receives from the Sun and must have an internal heatsource.
- Where the atmosphere is a few times denser than Earth's, temperatures are probablycomfortable by human standards. A human with a respirator could work in shirtsleeves.
- There has been speculation about life in Jupiter's atmosphere. All the raw materials are therebut turbulence would probably carry any organic chemicals into areas where temperatures are toohigh or too low before life could evolve. Still, one never knows...
- Jupiter has a ring which extends from 40,000 miles above the surface (160,000 miles indiameter) probably down to the surface. It looks brightest when seen from behind, that is, lookingtoward the Sun. This optical behavior suggests particles in the neighborhood of 1/10,000 inchdiameter.
Jupiter has at least 63 satellites as of 2008, numbered in order of discovery. Only the four largest(Galilean) satellites and one other have generally used names.
Small Inner Moons
Jupiter XV and XVI
Discovered by the Voyager spacecraft. They orbit outside Jupiter's ring about 80,000 milesfrom Jupiter's center in 7 hours, and are probably less than 40 km in diameter.
Amalthea (Jupiter V)
- A reddish, irregular body about 140 by 265 km. Red coating is sulfur escaping from Io.
- Fuzzy images were obtained that indicate some large craters and bright spots. Little isknown otherwise.
- Orbital radius 113,000 miles.
- Revolves around Jupiter in 12 hours.
Jupiter XIV (Thebe)
Orbits between Amalthea and Io, about 160,000 miles fromJupiter. It is about 30 miles in diameter.
The Galilean Satellites
Io (Jupiter I)
- 2261 miles in diameter.
- Orbital radius 262,000 miles.
- Orbits Jupiter in 42 hours.
- No atmosphere.
- Covered with reddish and orange deposits of sulfur.
- At least 8 active volcanoes.
- Source of heat is probably tidal forces from the other satellites and possibly electricalcurrents induced by Jupiter's magnetic field.
- Eruptions probably powered by sulfur and sulfur dioxide.
- Most geologically active body other than Earth (and rivals earth).
- No craters due to burial by eruptive deposits.
- Some faults.
Europa (Jupiter II)
- 1900 miles in diameter,
- Orbital radius 417,500 miles.
- Orbits Jupiter in 3 days, 13 hours.
- Smoothest body in solar system.
- Has an icy crust criss-crossed by dark cracks.
- Few craters.
- Probably has a thick ice crust over liquid water with a large rocky
- core. No atmosphere.
Ganymede (Jupiter III)
- 3240 miles in diameter,
- Orbital radius 666,000 miles.
- Orbits Jupiter in 7 days.
- Surface consists of large areas of cratered icy crust separated by bands
- of enigmaticgrooved terrain.
- Closest thing to plate tectonics seen anywhere but Earth.
- Density only 1.99.
- Probably mostly ice with some rocky material.
Callisto (Jupiter IV)
- 3040 miles in diameter.
- Orbital radius 1,170,000 miles.
- Orbits Jupiter in 16 3/4 days.
- Heavily cratered, with a spectacular large multi-ringed impact basin.
- Low density (1.76) suggests mostly ice composition.
- Icy crust flows, causing craters to have low relief.
The Small Outer Moons
None of these have been imaged at close range by spacecraft.
Jupiter VI, VII, X and XIII
- Orbit Jupiter at distances of about 7-7.5 million miles
- Take 240-260 days to orbit Jupiter.
- VI is about 100 miles in diameter, VII about 50, others about 20.
- Most orbit at distances of 13.2-14.7 million miles
- Periods of 600-800 days.
- All orbit backward relative to most motions in the Solar System.
- These are probably captured asteroids and are 20 miles or less in diameter.
- They fall into families with similar orbits and many are probably fragments of larger parent bodies shattered by impact.
Names of Minor Satellites
Galileo's discovery of the four large moons presented an unprecedented problem: what to name new objects in the Solar System. Galileo - no dummy - wanted to call them the "Medicean stars" in an effort to secure patronage from the powerful Medici family. The suggestion met with little approval. The moons should obviously be named for mythological characters connected with Jupiter but subordinate. Anyone who knows mythology knows that leaves out his wife Juno. Anyway, she has an asteroid named after her. However, Jupiter's principal hobby was having love affairs (Juno's was breaking them up and inflicting horrible vengeance on the lovers). So, following a suggestion by astronomer Simon Marius, Jupiter's satellites were named after Jupiter's lovers.
Oh, Ganymede was a boy. The ancient Greeks were cool with that.
Even Jupiter's colossal libido could hardly keep up with the tally of Jovial satellites, so beginning with satellite XXXIV (Euporie), satellites can also be named for descendants of Zeus.
- VI - Himalia
- VII - Elara
- VIII - Pasiphae
- IX - Sinope
- X - Lysithea
- XI - Carme
- XII - Ananke
- XIII - Leda
- XIV - Thebe
- XV - Adrastea
- XVI - Metis
- XVII Callirrhoe
- XVIII - Themisto
- XIX Megaclite
- XX- Taygete
- XXI - Chaldene
- XXII, Harpalyke
- XXIII - Kalyke
- XXIV - Iocaste
- XXV - Erinome
- XXVI - Isonoe
- XXVII - Praxidike
- XXVIII - Autonoe
- XXIX - Thyone
- XXX - Hermippe
- XXXI - Aitne
- XXXII - Eurydome
- XXXIII - Euanthe
- XXXV - Orthosie
- XXXIV - Euporie
- XXXVI - Sponde
- XXXVII - Kale
- XXXVIII - Pasithee
- John H. Wolfe, 1975, Jupiter. Scientific American, vol. 233, no. 3, pp. 118-129
- Andrew P. Ingersoll, 1976, The Meteorology of Jupiter. Scientific American, vol. 234, no. 3, pp. 46-59
- Laurence A. Soderblom, 1980, The Galilean Satellites of Jupiter. Scientific American, vol. 242, no. 1, pp. 88-101
- Andrew P. Ingersoll, 1981, Jupiter and Saturn. Scientific American, vol. 245, no. 6, pp. 90-111
- Torrance V. Johnson and Laurence A. Soderblom, 1983, Io. Scientific American, vol. 249, no. 6, pp. 56-67
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Created 20 May 1997, Last Update 11 January 2020