Deimos
Moon· orbits Mars
Deimos is the smaller, outer moon of Mars — a tiny body whose craters are partly buried under a blanket of fine regolith, giving it a smooth look.
Open in 3D viewSee Deimos in the live, interactive 3D map
Key facts
Mass
1.48 × 10¹⁵ kg
0.0000000201 Moon masses
Radius
6.2 km
Surface gravity
0.00256 m/s²
0% of Earth's
Day length
30.30 hours
Orbit around Mars
1.26 Earth days
Science
Physical
- Mass
- 1.48 × 10¹⁵ kg · 0.0000000201 Moon masses
- Radius
- 6.2 km
- Density
- 1,479 kg/m³ · 1.5× water
- Surface gravity
- 0.00256 m/s² · 0% of Earth's
- Escape velocity
- 5.64 m/s · 0% of Earth's
Orbit around Mars
- Distance from Mars
- 2,446,484 km
- Orbital period
- 30.30 hours
- Eccentricity
- 0
- Inclination
- 1.80 °
Rotation
- Rotation period
- 30.30 hours
- Tidal locking
- Tidally locked to its parent
Temperature
- Mean
- 233 K (-40 °C)
Composition
- Bulk composition
- Dark, carbonaceous-chondrite-like rock, like Phobos; a small, porous body.
Radiation & temperature
- Insolation
- 0.443 S⊕ · 44% of the sunlight Earth receives
- Geometric albedo
- 0.07
- Equilibrium temperature
- 223 K (-50 °C)
- Measured mean temperature
- 233 K (-40 °C)
- Greenhouse warming
- +10 K
Discovery & history
- Discovered
- August 12, 1877
- By
- Asaph Hall
- Method
- Visual discovery (telescopic)
- Name
- Deimos ('dread'), a son of the war-god Ares (Mars) in Greek myth.
Deimos is the smaller, outer moon of Mars, spotted by Asaph Hall on 12 August 1877, days before he found Phobos. Barely 12 km across, it is a dark, cratered lump — likely a captured asteroid — with gravity so weak you could almost throw a stone off it into space.
Images
Images from open archives · credit shown per image