Ganymede, largest of Jupiter’s 13 satellites, has bright “young” ray
craters; light, linear stripes resembling the outer rings of a very
large, ancient impact basin; grooved terrain with many faults; and
regions of dark, heavily cratered terrain. Among the Galilean
satellites, Ganymede probably has the greatest variety of geologic
processes recorded on its surface and may be the best example for
studying the evolution of Jupiter’s inner satellites. Imbedded within
Jupiter’s magnetosphere, Ganymede is subjected to the influences of the
corotating charged-particle plasma and an interaction may exist with
this plasma. No atmosphere has been detected.