This is an image of Europa
Click on image for full size
Courtesy of NASA
Icy moons are large or small moons which are composed
mostly of ice. These moons are unlike the earth's moon, which is made of silicate rock
Perfect examples of icy moons are 3 of the Galilean satellites, Europa, Ganymede, and Callisto. Except maybe for Europa and Triton, these moons have no atmosphere and no magnetosphere.
Surfaces of some of these moons, particularly that of Ganymede, reveal, however, that their evolution included activity in the interior which ultimately resulted in a change in the moon's appearance. Activity in the interior could also provide an environment suitable for life.
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