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 other
planets 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 into
liquid, then solid, hydrogen, possibly with a small rocky core.
- Jupiter's makeup is much like the Sun: 90% hydrogen and about 10% helium, with minor
amounts of methane (CH4), ammonia (NH3), water, carbon monoxide, ethane (C2H6) and other
- 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 size
of 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. This
field traps and accelerates particles from the solar wind and produces enormous radiation belts
and electrical currents.
- The radiation belts are so strong that the inner 3 Galilean satellites suffer radiation
bombardments that would be lethal to humans in a short time.
- All the spacecraft which have passed Jupiter absorbed hundreds of times the lethal radiation
dosage 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 heat
- Where the atmosphere is a few times denser than Earth's, temperatures are probably
comfortable 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 there
but turbulence would probably carry any organic chemicals into areas where temperatures are too
high 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 in
diameter) probably down to the surface. It looks brightest when seen from behind, that is, looking
toward the Sun. This optical behavior suggests particles in the neighborhood of 1/10,000 inch
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 miles
from 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 is
- Orbital radius 113,000 miles.
- Revolves around Jupiter in 12 hours.
Jupiter XIV (Thebe)
Orbits between Amalthea and Io, about 160,000 miles from
Jupiter. 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 electrical
currents 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
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 enigmatic
- 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
14 September 2018