Surface features of Jupiter moon Europa, illustration. Europa is the smallest of the four Galilean moons of Jupiter, and the second closest to the planet. Its surface is icy and relatively smooth. There is some evidence of large-scale movements of the ice (blue arrows at top), possibly supported by an underlying liquid mantle and driven by thermal processes within the moon. Ice geysers (centre) have been seen on this moon, producing jets of water-rich material rising 200 kilometres into space. The cracks then re-freeze, as seen at bottom, forming a distinctive pattern that has been observed from space.