How might Callisto's potential subsurface ocean differ fundamentally from Europa's ocean based on heating mechanisms?

Answer

Callisto's might be maintained passively, while Europa's requires active current heating.

Models suggest Callisto might have an ocean kept liquid by insulation, dissolved salts, or pressure passively, whereas Europa requires active, sustained tidal heating to maintain its liquid layer now.

How might Callisto's potential subsurface ocean differ fundamentally from Europa's ocean based on heating mechanisms?
GeologyastronomyPlanetary SciencemoonsTidal heating