Galileo Galilei was the first astronomer to observe Jupiter’s moon Ganymede on January 7, 1610.
Ganymede, made mostly of ice and rock, is the third farthest Galilean moon from Jupiter and is the planet’s largest satellite.
Ganymede is also the biggest moon, or satellite in our solar system.
Its surface is cratered, like Jupiter’s farthest moon, Callisto, and our Moon, but there are large areas of ridges and valleys.
This seems to result from tension due to the stretching of Ganymede’s surface.
Some areas split to form grooves while the surrounding area remains high.
Water appears to seep out from under the moon’s surface, which causes some of the craters and valleys to appear very bright.
Ganymede was named after mythological Ganymede, cupbearer of the Greek gods and Zeus’s beloved.