Moons of the Solar System
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Ganymede is not only the largest of Jupiter's moons, but it is also the biggest moon in the solar system--about three quarters the size of Mars. The bright spots in the picture are of young impact craters from a recent meteor bombardment. Ice covers one-third of Ganymede's surface.
Fun Fact: Ganymede can be seen from the surface of the Earth with the naked eye, as long as you look for it on a clear night without any light pollution.
Photo source: NASA