Cratered moon of SaturnA small moon with one huge impact
Mimas
Mimas carries a crater so large that the moon looks like a frozen warning about ancient collisions.
- Host
- Saturn
- Type
- Small icy moon
- Mean diameter
- 396 km
- Mean orbital radius
- 185,540 km
- Orbital period
- 0.94 days
- Surface gravity
- 0.064 m/s²
- Key feature
- Herschel crater
- Discovered
- 1789 · William Herschel
Mimas up close
NASA imagery
The crater that defines a world
Herschel is about 139 kilometres wide on a moon only 396 kilometres across. Its central peak and steep walls are the remains of an impact that nearly shattered the young Mimas.
The rest of the surface is saturated with craters, with no clear signs of broad volcanic resurfacing. Mimas is almost entirely water ice around a small rocky core.
A surprising interior
Cassini observations revealed an unusual wobble in Mimas's rotation. Recent analyses suggest the moon may contain a young or partly liquid ocean beneath its ice shell, though this remains an active research question.
Mimas also influences Saturn's rings and participates in orbital resonances with other moons. Its gravity helps create and maintain structures within the ring system.
Worth knowing
Herschel crater is named after the moon's discoverer, William Herschel.
Mimas's resemblance to the Death Star made it a pop-culture astronomy favourite.
The moon is one of Saturn's innermost major satellites.
Watch and explore
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Mimas: A Walk on Saturn's Cratered Moon Worlds Unvisited
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Research & further reading
Mission imagery and measurements are interpreted alongside orbital data. Follow the source links for the current NASA overview and precise satellite parameters.