Icy moons are a class of natural satellites with surfaces composed mostly of ice. An icy moon may harbor an ocean underneath the surface, and possibly include a rocky core of silicate or metallic rocks. It is thought that they may be composed of ice II or other polimorph of water ice. The prime example of this class of object is Europa.
All known icy moons belong to giant planets, whose orbits lie beyond the Solar System's frost line. An additional requirement is that a moon did not form in the inner region of a proto-satellite disk, which is too warm for ices to condense.
Europa is thought to contain 8% ice and water by mass with the remainder rock. Jupiter's outer two Galilean moons Ganymede and Callisto contain more ice since they formed further from the hot proto-Jupiter.
- ↑ Chaplin, Martin (2007-10-26). Ice-two structure. Water Structure and Science. Retrieved on 2008-01-02.
- ↑ Canup, Robin M.; Ward, William R. (2008). "Origin of Europa and the Galilean Satellites". Astrophysical Journal.
- ↑ 3.0 3.1 Rosaly Lopes and Robert M. Nelson (2009-08-06). Surface features on Titan form like Earth’s, but with a frigid twist. IAU. Retrieved on 2009-12-21.