Europa Rotating
Evidence has been mounting that beneath the vast planes of ice that cover Europa lies water -- liquid oceans that might be home to alien life . The smallest of Jupiter 's Galilean Moons (which include Io , Ganymede , and Callisto ), Europa's deep interior is composed of mostly of silicate rock . Upon close inspection, many surface cracks stop abruptly only to continue on somewhere else -- indicating surface plates that might be sliding . The above time-lapse sequence is a composite of images taken during the Voyager spacecraft flyby of the moon twenty years ago. Not all regions are resolved in high detail. The movie shows Europa during a complete rotation, which corresponds to a complete revolution around Jupiter since Europa always keeps the same face toward the giant planet. The cause of many of the surface colors on Europa also remains a topic of research .