Mimas - moon of Saturn

[from Wiki:] Mimas, also designated Saturn I, is a moon of Saturn which was discovered in 1789 by William Herschel. With a diameter of 396 kilometres (246 mi) it is the smallest astronomical body that is known to be rounded in shape because of self-gravitation. The surface area of Mimas is slightly less than the land area of Spain. The low density of Mimas indicates that it is composed mostly of water ice with only a small amount of rock. Due to the tidal forces acting on it, Mimas is noticeably prolate; its longest axis is about 10% longer than the shortest. The ellipsoidal shape of Mimas is especially noticeable in some recent images from the Cassini probe. Mimas's most distinctive feature is a giant impact crater 130 km (81 mi) across, named Herschel after the discoverer of Mimas.