Tethys
Major moon of Saturn, 1071 kilometers across.
Bulk parameters
Mass: 6.27 x 10^20 kg
Radius: 536 x 528 x 526 km
Mean density: 1000 kg/cm3
Visual geometric albedo: 0.9
Tethys clearly has a very old surface and has been heavily bombarded by impacts over time. The gash that cuts across the moon is known as Ithaca Chasma and the enormous impact crater that covers two fifths of the moon's surface is called Odysseus.
Orbital parameters
Semimajor axis: 294.66 x 10^3 km
Orbital period: 1.887802 days
Inclination: 1.86 degrees
Eccentricity: 0.0000
Tethys rotates synchronously - its rotation period is the same as the orbital period. This makes a "year" on Tethys the same length as a "day" - 1.89 standard days.
The moon orbits Saturn at a distance of 294 660 kilometers. Such a close proximity to Saturn subjects Tethys to tidal forces, the frictional heating of which likely helped keep it from cooling and solidifying longer than more distant moons. As a result Tethys appears somewhat less cratered than sister moons Rhea and Dione, which still bear the marks of their earliest impacts.
