Credit: NASA/JPL-Caltech/Space Science Institute Public Domain — NASA Media Usage Guidelines

MOON

Mimas

The "Death Star moon" — a small icy world marked by the enormous crater Herschel.

Orbits Saturn

About Mimas

Mimas, the smallest and innermost of Saturn’s major moons, is dominated by the 139 km wide impact crater Herschel — so large relative to the moon that Mimas was nicknamed the “Death Star moon” after the original Star Wars film. The impact that formed Herschel very nearly shattered Mimas.

Its unusually low density suggests a bulk composition of mostly water ice with a small rocky core. A 2024 reanalysis of Cassini tracking data identified a libration pattern best explained by a young (5-15 million years old) subsurface liquid water ocean — a surprising result for so small and ancient-looking a body.

Live · 3DSee Mimas in the Live 3D Solar SystemFly to Mimas and explore its orbit among the planets, moons & spacecraft in a full-screen interactive view.Launch 3D view

Physical Properties

Mean radius198 km

Mass3.7493e19 kg

Density1.148 g/cm³

Surface gravity0.064 m/s²

Escape velocity0.159 km/s

Rotation period22.6 h

Bond albedo0.962

Mean temp64 K

Orbit

OrbitsSaturn

Semi-major axis185,539 km

Eccentricity0.0202

Inclination1.574°

Orbital period0.942 d

Gallery

Hand-picked mission imagery of Mimas sourced from NASA and partner archives. Click any photo for full resolution and source attribution.

Mimas and its giant Herschel crater, from Cassini. NASA/JPL-Caltech/Space Science Institute · Public Domain u2014 NASA Media Usage Guidelines

Color view of Mimas near Herschel crater. NASA/JPL-Caltech/Space Science Institute

Imagery on this page is provided by the original mission teams. Full attribution terms: Image Rights & Credits.

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: 2026-06-08 01:37:02.