The Satellites of Jupiter

THE SATELLITES OF JUPITER

Jupiter has 16 satellites:
Adrastea, Amalthea, Ananke, Callisto, Carme, Elara, Europa, Ganymede, Himalia, Io, Leda, Lysithea, Metis, Pasiphae, Sinope and Thebe.

Image of the Amalthea satellite taken by the Voyager (Calvin J. Hamilton)

The discovery of Leda, one of the smallest and least known ones. (HST)

Satellite  Distance    Radius   Mass    Discoverer   Date of
           (x1000 km)   (km)     (kg)               discovery
---------  --------    ------  -------  ----------  ----------

Adrastea        129      10     1.91e16  Jewitt       1979
Amalthea        181      98     7.17e18  Barnard      1892
Ananke        21200      15     3.82e16  Nicholson    1951
Callisto       1883    2400     1.08e23  Galileo      1610
Carme         22600      20     9.56e16  Nicholson    1938
Elara         11737      38     7.77e17  Perrine      1905
Europa          671    1569     4.80e22  Galileo      1610
Ganymede       1070    2631     1.48e23  Galileo      1610
Himalia       11480      93     9.56e18  Perrine      1904
Io              422    1815     8.94e22  Galileo      1610
Leda          11094       8     5.68e15  Kowal        1974
Lysithea      11720      18     7.77e16  Nicholson    1938
Metis           128      20     9.56e16  Synnott      1979
Pasiphae      23500      25     1.91e17  Melotte      1908
Sinope        23700      18     7.77e16  Nicholson    1914
Thebe           222      50     7.77e17  Synnott      1979

Medicean or Galileian satellites

Io, Europa, Ganymede, Callisto are the largest ones and are named "Galileian satellites", since they have been observed, for the first time, by Galileo Galilei. The discovery that the center of motion of these satellites is not the Earth, but Jupiter, it has been one of the major arguments favoring the Copernican theory (or heliocentric) of the planetary motion. Ganymede, having a diameter of 5,280 km, is one of the largest satellites in the Solar System. The orbits of Io, Europa and Ganymede are connected by an orbital resonance, that is their orbital periods are in the ratio 1:2:4. This is caused by the tidal forces that are mutually exerted.

Voyager 2 image of Callisto, taken in 1979. The surface rich of craters is well seen. On the upper left, an enormous impact basin can be seen, with concentric ring features
I (Calvin J. Hamilton)

Chain of impact craters on the Callisto surface, imaged by the Galileo probe in 1996.
(NASA/JPL)

False color image of Europa, taken by the Galileo probe in 1996. The frozen lands have blue color.
(NASA/JPL)

Europa in natural colors (left) and false colors (right). The dark brown marks the rocky material, the frozen lands are light blue
(NASA/JPL)

Voyager 2 image of Europa
(Calvin J. Hamilton)

The whole disk of Ganymede. The dark region is called Galileo Regio, and its diameter is 3,200 km. The light spots are the most recent impact craters. (Calvin J. Hamilton)

An Io image taken by Voyager 1 in 1979. Its color is due to the abundance of sulfur. The light areas are rich in sulfur dioxide; volcanos can be noticed on the surface, and mountain chains are seen near the poles. Their height is 8 km (Calvin J. Hamilton)

Volcanic plumes 100 km high, on the surface of Io. The image was taken by Voyager 2 (1979). The eruption perhaps lasted more than four months.
(NASA/JPL)

Two images of Io taken by the Hubble Space Telescope, slightly more than one year apart. In the recent image, new light spots can be seen, perhaps caused by the eruption of the Ra Patera vulcan.
(HST)

ANIMATIONS

Europa, MPEG, 1.1 Mb (STScI)