The seventeenth of Saturn's known satellites and the third largest. It is 1436 km across and revolves around Saturn at a mean distance of 3.5 million km with a period of 79 days. The most unique and perhaps most remarkable feature on Iapetus is a topographic ridge 13 km higher than the surrounding terrain, as discovered in the images obtained with Cassini spacecraft. The ridge extends at least 1300 km almost exactly parallel with Iapetus's equator.
Iapetus was one of the Titan gods, sons of Ouranos (Heaven) and Gaia (Earth). Discovered 25 October 1671 by Jean-Dominique Cassini.