Tethys is one of the larger of the 18 moons of Saturn. This icy moon is heavily cratered and has many cracks and plains. It has a diameter of about 600 miles (1000 km). One huge ice trench, the Ithaca Chasma, is 40 miles (65 km) wide and extends over 3/4 of the way around the moon. It orbits at a mean distance of about 180,000 miles (294,000 km) from Saturn. Its orbital period is 45.3 hours. It was discovered by Cassini in 1684. It has a water-ice interior composition (density =1.21 gm/cm). The surface temperature is -187° C = -305° F.
In Greek mythology, Tethys, daughter of Uranus and Gaea (Hesiod, Theogony lines 136, 337 and Bibliotheke 1.2) was a Titaness and sea goddess who was both sister and wife of Oceanus. She was mother of the chief rivers of the world, such as the Nile, the Alpheus, the Maeander, and about three thousand daughters called the Oceanids. Considered as an embodiment of the waters of the world she may be seen as a counterpart of Thalassa, embodiment of the sea.