This image shows two views of the trailing hemisphere of Jupiter's ice-covered satellite, Europa. The left image shows the approximate natural color appearance of Europa. The image on the right is a false-color composite version to enhance color differences in the predominantly water-ice crust of Europa. There are a number of very good lines of evidence which suggest that beneath this icy cover lies an ocean- and many have speculated that if there is an ocean, there could be hydrothermal vents (and maybe even microbes!).