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MOON

Tethys

Low-density icy moon with the giant crater Odysseus and the enormous rift Ithaca Chasma.

Orbits Saturn

Almost pure water ice (density just below that of water).
Odysseus crater spans 450 km u2014 40% of the moon's diameter.
Ithaca Chasma is a 2,000 km long rift, thought to have formed as the interior water froze and expanded.

Physical Properties

Mean radius531 km

Mass6.17449e20 kg

Density0.984 g/cm³

Surface gravity0.146 m/s²

Rotation period45.31 h

Bond albedo0.8

Mean temp86 K

Orbit

OrbitsSaturn

Semi-major axis294,672 km

Eccentricity0.0001

Inclination1.12°

Orbital period1.888 d

Sources & Further Reading

Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-04-18 18:19:24.

Tethys is Saturn’s fifth-largest moon and one of the icy satellites observed by Cassini. Its density of 0.984 g/cm³ is just below water’s, implying it is composed almost entirely of water ice. Its surface is dominated by Odysseus, a giant multi-ring impact basin 450 km across, and by Ithaca Chasma, a 2,000 km long canyon system believed to have formed when Tethys’s global subsurface ocean froze and expanded the crust.