Discovery of Tethys

Tethys is a mid-sized icy moon of Saturn, discovered by Giovanni Domenico Cassini at the Paris Observatory on the same night as Dione. Its name was later suggested by John Herschel and comes from the Titan Tethys of Greek mythology. The moon is made almost entirely of water ice and has a low density, and its surface is dominated by the huge Odysseus impact crater and by a vast valley system, Ithaca Chasma, that stretches most of the way around it. Tethys shares its orbit with two tiny moons, Telesto and Calypso. The Cassini spacecraft examined it during several close flybys.

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