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According to Greek mythology, Ganymede was a son of Tros, the first king of the land of Troy. Ganymede lived on the island of Crete in the Mediterranean Sea, and tended sheep there on the slopes of Mount Ida. One day, Zeus - the mightiest of all the Greek gods - caught a glimpse of the handsome young boy as he was tending his sheep, and thought he would be a perfect addition to the court of the Gods. Zeus changed shape into that of an eagle, swooped down onto the craggy slopes of Mount Ida, and carried the boy off to Mount Olympus - home of the gods - to serve as thier cup bearer. Now it so happens that this position was already filled by Hebe, the daughter of Zeus and Hera. When Ganymede arrived at the royal court there began a furious competition between Hebe and Ganymede for the honor of serving the gods. Eventually Ganymede won the post, and stayed on also as the beloved companion to Zeus. Hebe went on to marry Heracles. To honor the events surrounding the elevation of Ganymede to "Cup bearer and servant of the gods," Zeus placed his shape of an eagle, the shape he assumed when abducting Ganymede to Olympus, into the heavens as the constellation Aquila (eagle), and immortalized Ganymede as the constellation Aquarius (water bearer). |
Photograph courtesy of JPL/NASA
| Mean orbital distance (from centre of Jupiter) | 1070000 km |
| Diameter | 5262 km |
| Mass | 1.48x10^20 tonnes |
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Ganymede is the third of the so called Gallilean Moons of the planet Jupiter. The other three being Io, Europa and Callisto. Thay get their name from the 17th centuary astronomer Gallileo Galilei. He discovered them in 1610 with one of the very first telescopes ever made. |
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Ganymede is the largest satellite in the solar system. It is larger in diameter than Mercury but only about half its mass. Ganymede is much larger than the planet Pluto. Before the Galileo spacecraft encounters with Ganymede, it was thought that Ganymede and Callisto were composed of a rocky core surrounded by a large mantle of water or water ice with an ice surface and that Titan and Triton (moons of Saturn and Uranus) were similar. However, indications from the Galileo data now suggest that Callisto has a uniform composition while Ganymede is made up of three different layers: a small molten iron or iron/sulphur core surrounded by a rocky silicate mantle with an icy shell on top. In fact, Ganymede may be similar to Io with an additional outer layer of ice. |
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