Jupiter and its moons. Computer artwork of a view across an impact crater in the surface of Ganymede, towards Jupiter. Ganymede is the largest of the many moons that orbit Jupiter. In the middle of the impact crater, which measures about 10 miles in diameter, is a central peak that formed when the energy of the impact liquefied the crust long enough for it to rebound upward before solidifying. At upper right is Ganymede's sister satellite Europa. To the lower left of Jupiter is the volcanic satellite Io.