Saturn’s second largest moon is Rhea, named for the mother of Zeus in Greek mythology. The satellite has albedo features, no atmosphere, and visible ice deposits. This moon has a diameter of 1530 kilometers and orbits 527,040 kilometers from Saturn. Rhea is believed to consist of a small rocky core with the rest made up of water ice. In sunlight, Rhea can get as warm as -174 degrees C and as cold as -220 degrees C on its dark side.
This satellite was discovered in 1672 by the Italian-born French astronomer Giovanni Domenico Cassini. Rhea has been visited by Voyager 1 in 1980 and will be visited by the aptly named Cassini probe in 2004.
Like Earth’s Moon, Rhea has a synchronous rotation. This means that its period of rotation, 4.5175 days, is the same as its orbit around Saturn. Satellites with a synchronous rotation continously face the same hemisphere, their leading hemisphere, towards the object they rotate around. Rhea’s leading hemisphere is bright and well cratered. Its craters, however, are not deep, tending to have shallow walls. By contrast, its trailing hemisphere has several bright splotches on an otherwise smooth, dark surface.
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