Europa images of a geologically diverse world hint that an ocean may currently or may have once existed beneath the icy surface. For Ganymede, good quality high resolution imaging by Galileo showed that tectonic forces formed the main geologic features. Callisto offered an interesting surprise. Formerly thought to be densely cratered at all scales, it was found that small craters are rare and the surface is covered by a planet-wide layer of dark material. If the Galileo spacecraft survives the tortuous radiation environment near Io, a proposed extension of the mission may involve further flybys of these intriguing worlds and culminate in a joint investigation of Jupiter and its environment by Galileo and the Cassini spacecraft.
North is to the top of the individual pictures.
The SSI Education and Public Outreach webpages were originally created and managed by Matthew Fishburn and Elizabeth Alvarez with significant assistance from Kelly Bender, Ross Beyer, Detrick Branston, Stephanie Lyons, Eileen Ryan, and Nalin Samarasinha.