Europa, a satellite of Jupiter
Europa. Voyager 2 photograph of Europa, one of the Galilean moons of Jupiter, taken on 9 July 1979. It is thought that the crust of the moon is water ice about 50 kilometres thick surrounding a rocky interior. The surface of Europa is featureless except for the striking curvilinear markings which are clearly seen in this image. The individual dark bands are 20 to 40km in width, stretch for thousands of kilometres across the face of the moon but have elevations of only a few hundred metres. The smooth surface may indicate an almost slush-like mantle below the crust which fills impact craters and freezes, maintaining the smooth appearance.