Moons · Space Codex
Tethys
Almost pure water ice, Tethys is less dense than water itself.
Ice moon split by a giant canyon
At a glance
Key points
A crater two-fifths its width and a canyon running three-quarters of the way around it record a violent past.
- Less dense than water: almost pure ice
- Odysseus crater is two-fifths the moon's width
- Ithaca Chasma runs about 2,000 km
Surface
Odysseus crater spans about 400 km, nearly two-fifths of the moon's diameter, yet its floor has relaxed flat, a sign the interior was soft when it formed. Ithaca Chasma, a valley system about 100 km wide and 2,000 km long, wraps most of the way around the moon.
Companions
Two tiny moons, Telesto and Calypso, share Tethys's orbit, held at the stable Lagrange points 60° ahead and 60° behind it.
What we still don't know
Whether Ithaca Chasma formed as the interior froze and expanded or as a result of the Odysseus impact.
Missions
- 1977–
Jupiter 1979, Saturn 1980; interstellar space since 25 Aug 2012.
- 1977–
The only spacecraft to visit Uranus (1986) and Neptune (1989); interstellar since 5 Nov 2018.
- 1997–2017
Cassini–Huygens
NASA / ESA / ASICompletedOrbited Saturn 2004–2017 and ended by diving into the planet.
First-hand · our 3D model
How we render it
Tethys is a sphere wrapped in a global map built from USGS and NASA spacecraft mosaics.
It is drawn at about 4.3% of Saturn's radius, enlarged from its true 0.91% so it stays visible. It orbits in Saturn's equatorial frame, inclined 1.1°, with a 1.89-day period kept in true ratio to its neighbours, and keeps one face towards Saturn.
Moon sizes and orbits are compressed so a whole system fits on screen, but never reordered: each moon is drawn at 0.72 × (true size ratio)^0.6 of its planet, capped so no large moon is drawn bigger than it really is, and orbit distances are log-compressed into a band that clears the planet's rings. Orbital periods keep their true ratios, every moon is tidally locked, and on lighter devices only the two largest moons of each planet are drawn.
Related entries
- SaturnRinged gas giant
Sources
- JPL Solar System Dynamics: satellite physical parameters (opens in a new tab)
- JPL Solar System Dynamics: satellite mean orbital elements (opens in a new tab)
- NASA NSSDC Saturnian Satellite Fact Sheet (opens in a new tab)
- NASA Science: Tethys (opens in a new tab)
Last reviewed against these sources. Built from public NASA, ESA and JPL data; not affiliated with or endorsed by any agency.