Saturn's moon Tethys. - stock photo

August 30, 2007 - The Crown of Tethys. the vast expanse of the crater Odysseus spreads out below Cassini in this mosaic view of Saturn's moon Tethys. The crater (450 kilometers or 280 miles across) is a remarkably well-preserved example of an ancient multi-ringed impact basin: The outer ring is defined by steep, cliff-like walls that descend to generally broad internal terraces. The inner ring is formed by a prominent, crown-shaped, 140-kilometer (88-mile) diameter circular band of icy mountains. Multi-ring basins are seen on rocky bodies as well as icy ones. The complex internal structure and multi-ringed nature of these very large basins are believed to arise from the rebound of intense shock waves that penetrated the body at the time of impact.