Icy moonsare a class ofnatural satelliteswith surfaces composed mostly ofice. 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 ofice IIor other polymorphof water ice.The prime example of this class of object isEuropa. Icy moons warmed bytidesmay be the most common type of object to have liquidwater, and thus the type of object most likely to havewater-basedlife. Some icy moons exhibitcryovolcanism, as well as geysers. The best studied example isSaturn'sEnceladus.
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