That's No Moon...Oh, Wait, It Is

Looking much like the fictional Death Star, Mimas is a moon of Saturn that was discovered in 1789 by William Herschel. It is named after Mimas, a son of Gaia in Greek mythology, and is also designated Saturn I.
Mimas' low density indicates that it is composed mostly of water ice with only a small amount of rock. Due to the tidal forces acting on it, the moon is not perfectly spherical; its longest axis is about 10% longer than the shortest.
Mimas' most distinctive feature is a colossal impact crater 130 km across, named Herschel after the moon's discoverer. Herschel's diameter is almost a third of the moon's own diameter; its walls are approximately 5 km high, parts of its floor measure 10 km deep, and its central peak rises 6 km above the crater floor. If there were a crater of an equivalent scale on Earth it would be over 4,000 km in diameter, wider than Canada.
Mimas closely resembles the Death Star in the Star Wars films, which is also said to be several hundred kilometers in diameter. This is purely coincidental; the Death Star was designed and created long before the first close-up photographs of Mimas were taken. Click on the picture for a larger view.

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