Tethys
Tethys information Average distance from Saturn: 294660 km (0.002 AU) Equatorial radius: 535.6 x 528.2 x 525.8 km (Diameter: 1071.2 km) Mass: 627000000000000000000 kg Siderial orbit period (length of year): 1.887802160 earth days Orbital eccentricity: 0.00000 Orbital inclination to ecliptic: 1.86 degrees		Tethys, Saturn III
Tethys In Greek mythology Tethys was a Titaness and sea goddess who was both sister and wife of Oceanus. Discovered by Cassini in 1684. Tethys' low density indicates that it is almost completely composed of water ice, similar to Dione and Rhea. The western hemisphere is dominated by a huge impact crater, called Odysseus, whose 400 km diameter is nearly 2/5 of that of Tethys itself (right). That such an impact didn't shatter Tethys completely indicates that it may have been liquid or at least not very solid at the time. The crater is now quite flat (or more precisely, it conforms to Tethys' spherical shape), like the craters on Callisto, without the high ring mountains and central peaks commonly seen on the Moon and Mercury. The second major feature seen on Tethys is a huge valley (called Ithaca Chasma) 100 km wide and 3 to 5 km deep which runs 2000 km or 3/4 of the way around Tethys' circumference (above). Clearly then, Tethys has not always been frozen solid. At some point in its past it was probably liquid. The impact craters from that era have been smoothed out. As it froze and expanded, the surface must have cracked to accommodate the extra volume producing Ithaca Chasma. The smaller impact craters we see today are more recent. There are no albedo features on Tethys as there are on Rhea and Dione. Telesto and Calypso orbit in Tethys' Lagrange points (60 degrees ahead and behind Tethys in the same orbit).
More Discovered by G.D. Cassini in 1684
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