Its frozen shell is encrusted with a layer of white and orange ice. The endless twisting and pulling of Jupiter’s gravity leaves a surface crisscrossed by deep valleys, ridges, and not yet fully understood “chaos zones” of deep tectonic activity. Its immense dark oceans, heated by underwater volcanoes, are hidden by this icy surface — that is, except for when it explodes outwards in titanic geysers, shooting plumes of liquid water hundreds of miles into space.No, this isn’t science fiction — this is Europa, the hauntingly beautiful yet bizarre ocean moon of Jupiter. Scientists have called Europa “the most...