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Mimas from Cassini on Jan. 16, 2005, showing crater Herschel
Mimas as seen by the Cassini Orbiter on Jan. 16, 2005 from a range of 213,000 km (132,000 miles). Prominent is the crater Herschel with its giant central peak.
A moon of Saturn, discovered on September 17, 1789, by William Herschel. It is also known as Saturn I because it was the innermost of the seven moons of Saturn known when this numbering system was adopted. In Greek mythology, Mimas was a Titan who was slain by the god Hercules.

Its low density suggests a composition that is primarily water ice. Mimas is heavily cratered, although the cratering is not uniform. While most of the surface is covered with craters up to and exceeding 40 km (25 miles) in diameter, in the southern polar region craters larger than 20 km (12 miles) are generally absent. Preeminent is the crater Herschel which, at 130 km (80 miles) across, spans more than one third the diameter of the whole moon, and has a central peak that rises 6 km (4 miles) above the crater floor. Had the impact that caused it been much bigger, it may have split Mimas apart. As it is, traces of fracture marks are evident on the opposite hemisphere. Most of the other craters on Mimas are named after characters in Camelot.

From a distance, the satellite bears a striking resemblance to the Death Star in the Star Wars films!

discovery 1789, by William Herschel
semimajor axis 185,404 km (115,229 miles)
diameter 415 × 394 × 381 km (258 × 245 × 237 miles)
mean density 1.15 g/cm3
escape velocity 0.161 km/s (580 km/h)
orbital period 0.942 day (22 h 36 min.)
orbital eccentricity 0.020
orbital inclination 1.51°
axial period synchronous
visual albedo 0.77

Mimas as depicted by Chesley Bonestell
Mimas as portrayed by the artist Chesley Bonestell. © Bonestell Space Art, used with permission

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   • Saturn, moons

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