Not to be confused with Thetis, a Nereid, wife of the sea god Poseidon.

Also, the name of an ocean that stretched from present-day Southern Europe to South-East Asia 200 million years ago.

Plate tectonics, in particular, the northward movement of Africa (then Gondwanaland) against the Eurasian plates (then Laurasia), gradually narrowed it to a west-east band; already closed off at the West end, the collision of the India plate onto the Asian continent, 50 million years ago, closed it off from the Indian ocean to form an inner sea that started to dry up, leaving the present-day Aral Lake, the Caspian Sea, the Black Sea and the Mediterranean as remains. The Mediterrean and Black Sea were reconnected to the oceans very recently (the opening of the Bosporus may well be attested in surviving legends); the other remains are being used up at record speed by irrigation.

Discovered by            Giovanni Domenico Cassini
Date of Discovery        1684
Distance from Saturn     294,660 km
Radius                   535.6 × 528.2 × 525.8 km
Mass                     6.27 × 10^23 g
Orbital Eccentricity     0.00000
Orbital Inclination      1.86°
Orbital Period           1.887802160 days
Rotational Period        Synchronous
Density (gm/cm3)         1.21 

Like Dione and Rhea, this satellite is heavily cratered and almost completely composed of water ice. The largest crater, named Odysseus, seems to be partially smoothed out, indicating a period of the moon's history when it partially liquefied. Tethys differs somewhat from the other two in that its surface is also heavily marked by cracks and faults. It is believed that these were caused by the surface freezing before the core. One of these cracks, called Ithaca Chasma, is approximately 65 km wide and covers almost 3/4 of the moon's circumference.

Tethys shares its orbit with two Trojan moons, or bodies sharing its orbit at the Lagrange points. Telesto precedes Tethys by 60°, and Calypso trails 60° behind. If you plan on going, bring a coat because the surface temperature is -187° C.

Sources:
NASA.gov
space.com

Τηθυς

One of the primordial divinities of the Greek theogonies. She was the personification of the feminine fecundity of the sea, and was the daughter of Uranus and Gaia, and the youngest of the Titanides (Table 5 and Table 12). She married Oceanus, one of her brothers, by whom she had more than 3,000 children who were all the rivers of the world. Tethys brought up HERA who had been entrusted to her by Rhea during Zeus' struggle against Cronus. As a sign of her gratitude, Hera managed to reconcile Tethys and Oceanus who had fallen out. Tethys' dwelling was usually situated in the Far West, beyond the country of the Hesperides, in the region where, each evening, the Sun comes to the end of its course.

{E2 DICTIONARY OF CLASSICAL MYTHOLOGY}

Te"thys (?), n. [NL., fr. Gr. an oyster, or a kind of ascidian.] Zool.

A genus of large naked mollusks having a very large, broad, fringed cephalic disk, and branched dorsal gills. Some of the species become a foot long and are brilliantly colored.

© Webster 1913.