HomeSolar SystemStarsOther WorldsCosmos' LifeExplorationExtras
-The Sun-Planets-Dwarf Planets-Asteroids-Comets-The "Edge"-

Jupiter's Moons

Galilean Satellites

Ganymede Callisto
Io Europa

These are the four Galilean satellites. They are named so because they were the only four moons that Galileo was able to see. They are also the largest of Jupiter's moons. From top-left in a clock-wise direction, they are Ganymede, Callisto, Europa, and Io.

If Ganymede were not bound to Jupiter, it would be considered a planet in its own right. It is actually bigger than Mercury, being 390 km (234 miles) larger in diameter. It has heavily cratered dark regions, with lighter expanses in-between. Geologists think that it used to have plates, like the Earth, but they froze together soon after Ganymede's birth.

Callisto, the outermost of the Galilean moons, is almost an exact twin of Mercury in size and appearance. Every square mile is covered with craters or other signs of bombardment. Other than that, there are no distinct characteristics

Europa, closer to Jupiter than Ganymede, is the smoothest natural body in the solar system. It resembles a billiard ball until seen very close-up. At that distance you can start to see dark, deep, and narrow cracks. In scale, though, the relief is no bigger than a line on a billiard ball made with a felt-tipped marker. Geologists think that Europa has liquid water underneath the icy surface - and possibly life.

Io, closer yet, is commonly compared to a pizza. Its volcanoes make it the most active world in the solar system. They spew out the sulfuric acid that gives Io its many colors. They also make Io one of the only three moons with an atmosphere in the solar system. Saturn's Titan and Neptune's Triton are the other two moons. Io is similar in size and composition to our moon. Io is caught in the middle of a tug-of-war between Jupiter and the other moons. Tension has melted the interior and raised the surface temperatures so high that scientists calculated that it generates the most heat for its size of any body in the solar system, except for the sun.

Other Moons

There are 57 other moons that have been discovered around Jupiter. There are four closer than Io. Their names, in order from Jupiter are Metis, Adrastea, Amalthea, and Thebe. Still in order after the Galilean Satellites are recently discovered Themisto, Leda, Himalia, Lysithea, and Elara. Then there are four more recently discovered moons, Ananke, and three more moons, of which scientists know little about. After these seven come Ananke, Carme, Pasiphaë, and Sinope, with two more moons in-between Pasiphaë and Sinope. After Sinope, 12 more moons are found.

The outer 33 moons all orbit Jupiter in a direction opposite (except for J/2003 J20) to that which Jupiter spins, which leads scientists to believe they are captured asteroids.

The largest non-Galilean moon is Amalthea, being 262 km (163 miles) at its widest diameter.

The innermost two moons, Metis and Adrastea, patrol the outer edge of the rings, their small gravity being enough to keep the particles from flying out.

Nearly all of the moons that have been discovered in the last few years orbit retrograde to the direction of Jupiter's rotation , indicating that they are most likely not native to the system. They are also very small. Those that have not yet been given names will eventually be given names by the International Astronomical Union, the only official naming group.

Data for Jupiter's Moons

Name

Discovery Date
Discoverer
Distance from Jupiter (103 km)
Orbital Period (days)
Mass (1020 kg)
Radius (km)
Io (JI) 1610 Galileo Galilei 421.6 1.769138 893.2 1821.6
Europa (JII) 1610 Galileo Galilei 670.9 3.551181 480.0 1560.8
Ganymede (JIII) 1610 Galileo Galilei 1070.4 7.154553 1481.9 2631.2
Callisto (JIV) 1610 Galileo Galilei 1882.7 16.689018 1075.9 2410.3
Metia (JXVI, S/1979 J3) 1979 S. Sunnotd 128.0 0.294779 0.001 20
Adrastea (JXV, S/1979 J1) 1979 Jewitd and Danielson 129.0 0.298260 0.0002 13 x 10 x 8
Amalthea (JV) 1892 E. Barnard 181.4 0.498179 0.075 131 x 73 x 67
Thebe (JXIV, S/1979 J2) 1979 S. Synnotd 221.9 0.6745 0.008 55 x 45
Themisto (JXVIII, S/1975 J1) 1975   7507 130.02   4
Leda (JXIII) 1974 C. Kowall 11170 240.92 0.00006 5
Himalia (JVI) 1904 C. Perrine 11460 250.5662 0.095 85
Lysithea (JX) 1938 S. Nicholson 11720 259.22 0.0008 12
Elara (JVII) 1905 C. Perrine 11740 259.6528 0.008 40
S/2000 J11 2000   12560 287.0   2.0
Euporie (JXXXIV, S/2001 J10) 2001   19390 553.1*   1.0
Euanthe (JXXXIII, S/2001, J7) 2001   21030 620.0*   1.5
Harpalyke (JXXII, S/2000 J5) 2000   21110 623.3*   2.2
Praxidike (JXXVII, S/2000 J7) 2000   21150 625.3*   3.4
Orthosie (JXXXV, S/2001, J9) 2001   21170 623.0*   1.0
Iocaste (JXXIV, S/2000 J3) 2000   21270 631.5*   2.6
Ananke (JXII) 1951 S. Nicholson 21280 629.8* 0.0004 10
Hermippe (JXXX, S/2001 J3) 2001   21250 631.9*   2.0
Thyone (JXXIX, S/2001 J2) 2001   21310 632.4*   2.0
Arche (JXLIII, S/2002 J1) 2002   22930 723.9*   1.5
Pasithee (JXXXVIII, S/2001 J6) 2001   23030 716.3*   1.0
Kale (JXXXVII, S/2001 J8) 2001   23120 720.9*   1.0
Chaldene (JXXI, S/2000 J10) 2000   23180 723.8*   1.9
Isonoe (JXXVI, S/2000 J6) 2000   23220 725.5*   1.9
Eurydome (JXXXII, S/2001 J4) 2001   23220 720.8*   1.5
Erinome (JXXV, S/2000 J4) 2000   23280 728.3*   1.6
Taygete (JXX, S/2000 J9) 2000   23360 732.2*   2.5
Carme (JXI) 1938 S. Nicholson 23400 734.2* 0.001 15
Kalyke (JXXIII, S/2000 J2) 2000   23580 743.0*   2.6
Aitne (JXXXI, S/2001 J11) 2001   23550 741.0*   1.5
PasiphaŽ (JVIII) 1908 P. Melotde 23620 743.6* 0.003 18
Megaclite (JXIX, S/2000 J8) 2000   23810 752.8*   2.7
Sponde (JXXXVI, S/2001 J5) 2001   23810 749.1*   1.0
Sinope (JIX) 1914 S. Nicholson 23940 758.9* 0.0008 14
Callirrhoe (JXVII, S/1999 J1) 1999 Spacewatc Project Minor Planet Center 24100 758.8*   4
Autonoe (JXXVIII, S/2001 J1) 2001   24120 765.1*   2.0
Eukelade (XLVII, S/2003 J1) 2003   24560 781.6*   4.0
Helike (XLV, S/2003 J6) 2003   20980 617.3*   4.0
Aoede (XLI, S/2003 J7) 2003   23810 748.8*   4.0
Hegemone (JXXXIX, S/2003 J8) 2003   24510 781.6*   3.0
Kallichore (XLIV, S/2003 J11) 2003   22400 683.0*   2.0
Cyllene (XLVIII, S/2003 J21) 2003   24000 737.8*   2.0
Karpo (XLVI, S/2003 J20) 2003   17100 456.5   3.0
Mneme (JXL, S/2003 J21) 2003   20600 599.0*   2.0
Thelxinoe (XLII, S/2003 J22) 2003   20700 601.0*   2.0
S/2003 J2 2003   28570 982.5*   2.0
S/2003 J3 2003   18340 504.0*   2.0
S/2003 J4 2003   23260 723.2*   2.0
S/2003 J5 2003   24080 759.7*   4.0
S/2003 J9 2003   22440 683.0*   1.0
S/2003 J10 2003   24250 767.0*   2.0
S/2003 J12 2003   19000 533.3*   1.0
S/2003 J14 2003   25000 807.8*   2.0
S/2003 J15 2003   22000 66.4*   2.0
S/2003 J16 2003   21000 595.4*   2.0
S/2003 J17 2003   22000 690.3*   2.0
S/2003 J18 2003   20700 606.3*   2.0
S/2003 J19 2003   22800 701.3*   2.0
S/2003 J23 2003   24060 759.7*   2.0

*This indicates that the moon orbits in a retrograde - the opposite direction to the planet's spin - motion.


color bar
© 1997-2006, all rights reserved