Mimas
Moon· orbits Saturn
Mimas is a small, heavily cratered ice moon of Saturn dominated by the 130-km crater Herschel, which gives it an uncanny resemblance to the Death Star.
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Key facts
Mass
3.75 × 10¹⁹ kg
0.000511 Moon masses
Radius
198 km
11% of our Moon's radius
Surface gravity
0.0637 m/s²
1% of Earth's
Day length
22.62 hours
Orbit around Saturn
22.6 hours
0.94 Earth days
Science
Physical
- Mass
- 3.75 × 10¹⁹ kg · 0.000511 Moon masses
- Radius
- 198 km · 11% of our Moon's radius
- Density
- 1,150 kg/m³ · 1.1× water
- Surface gravity
- 0.0637 m/s² · 1% of Earth's
- Escape velocity
- 159 m/s · 1% of Earth's
Orbit around Saturn
- Distance from Saturn
- 4,307,691 km
- Orbital period
- 22.62 hours
- Eccentricity
- 0.02
- Inclination
- 1.60 °
Rotation
- Rotation period
- 22.62 hours
- Tidal locking
- Tidally locked to its parent
Temperature
- Mean
- 64 K (-209 °C)
Composition
- Bulk composition
- Almost entirely water ice with a little rock; gravity data hint at a young internal ocean.
Radiation & temperature
- Insolation
- 0.0112 S⊕ · 1% of the sunlight Earth receives
- Bond albedo
- 0.55 · reflects 55% of incoming sunlight
- Equilibrium temperature
- 74 K (-199 °C)
- Measured mean temperature
- 64 K (-209 °C)
Discovery & history
- Discovered
- September 17, 1789
- By
- William Herschel
- Method
- Visual discovery (telescopic)
- Name
- Mimas, one of the Giants of Greek myth.
Herschel discovered Mimas in 1789 with the great reflecting telescope he had just built. Its enormous Herschel crater — a third of the moon's width — gives it an uncanny resemblance to the Death Star, and wobbles in its motion hint at a hidden ocean beneath the ice.
Images
Images from open archives · credit shown per image