Many colors and high albedo due to different compounds of sulfur. Tidal stresses of Jupiter and other moons creates internal heating to power the volcanoes. Thin atmosphere of SO 2 . Probable core with iron compounds and molten mantle. Average temperature 27 degC with hotter spots.
Water ice has high albedo.
Very few craters means a young surface. Perhaps a 100 km deep layer of slush and ice heated by tidal flexing. Evidence of rotation of ice plates. Probable iron core and rocky mantle. Grooves are 1km high and 10-15 km apart.