Surface movement on Europa. Cutaway computer illustration showing the surface structure of Europa, one of the four Galilean moons of Jupiter. The surface crust of Europa is made of water ice, which forms large blocks of ice, similar to polar ocean ice floes on Earth. The absence of large craters suggests that the surface is fairly new, having been refreshed in recent geological history. It is believed that this indicates a large body of water (blue, bottom) may exist beneath the surface crust, enabling the movement of surface plates, similar to plate tectonics on Earth.