Definition
An icy moon is a natural satellite mainly covered with water ice or other volatile ices. Its surface is bright, often marked by fractures, cracks, and smooth regions indicating renewal.
Structure
The typical structure consists of a rigid ice crust, whose thickness may vary, covering a more ductile mantle or an internal liquid ocean. The central core may be rocky or metallic, providing a dense base. The internal layers interact through heat conduction and gravitational deformations.
Surface
The surface shows fractured terrains, grooves, and sometimes cryovolcanic deposits. Geysers or plumes may erupt from fissures, ejecting water and particles into space. The lack of many craters may indicate recent surface renewal.
Internal Functioning
Beneath the crust, an internal ocean may persist thanks to heat generated by tidal forces or internal radioactivity. This ocean maintains a dynamic balance between surface ice and deeper layers.
Evolution
Icy moons evolve through cycles of solidification and partial melting. Tidal stresses and impacts shape their geology. Over time, the crust thickness may increase or fracture depending on the amount of internal heat.
Limitations
The limitations of an icy moon lie in its thermal and orbital stability. Too far away, it freezes completely; too close, it may lose its ice layer through sublimation or become too active, constantly reshaping its surface.