Given the geological features present, there is strong evidence that Europa contains a liquid water ocean beneath its ice shell. Further evidence was provided by the Galileo space craft, which was mounted with a magnetometer to detect the magnetic fields around Jupiter and its moons. Jupiter has a varying magnetic field which was found to induce a magnetic field around Europa. In order for a field to be induced, a layer of electrically conducting material must lie below the ice shell. This layer is most likely a ~100 km deep salty ocean (Khurana et al. 1998). If this is true, then Europa is a prime candidate for extra terrestrial life.

Overview
Tidal Heating
Craters
Ridges
Bands
Chaos
Bibliography