Two views of Ganymede’s patchwork surface taken by Galileo around 1997. While some areas appear geologically older (as demonstrated by the record of impact cratering) some seemingly younger areas recall the fracturous features seen at Europa. Many theorize, just as they do at Europa, that there may be a global ocean of water beneath the surface at Ganymede. However, it is also assumed (if if this does exist) that this ocean would be more shallow and under a much thicker crust of rock hard ice than that of Europa.