Tethys

Tethys is Saturn's third large inner moon, discovered by Giovanni Cassini in 1684. It orbits 183,000 mi (295,000 km) from Saturn, with an orbital period of 1.89 days, and has a diameter of 660 miles (1070 km).

Tethys is an icy body similar in nature to Dione and Rhea, and is composed almost entirely of water ice. Tethys's icy surface is heavily cratered and contains cracks caused by faults in the ice. There is an enormous fissure on Tethys, called Ithaca Chasma, which is about 40 miles (65 km) wide and extends three-fourths of the way around Tethys' circumference. The opposite hemisphere displays an enormous crater, Odysseus, almost as big in relation to Tethys as the crater Herschel is on Mimas. The shock of the impact which created Odysseus may have also formed Ithaca Chasma.