The Galilean satellites

NASA's Galileo mission to Jupiter and improved Earth-based observing capabi lities have allowed major advances in our understanding of Jupiter's moons lo, Europa, Ganymede, and Callisto over the past few years, Particularly ex citing findings include the evidence for internal Liquid water oceans in Ca llisto and Europa, detection of a strong intrinsic magnetic field within Ga nymede, discovery of high-temperature silicate volcanism on lo, discovery o f tenuous oxygen atmospheres at Europa and Ganymede and a tenuous carbon di oxide atmosphere at Callisto, and detection of condensed oxygen on Ganymede , Modeling of Landforms seen at resolutions up to 100 times as high as thos e of Voyager supports the suggestion that tidal heating has played an impor tant role for lo and Europa.