Cosmic Scale
Deimos
Moon of Mars · 23,460 km from Mars
How big is Deimos?
Deimos is about 12.4 km across.
See Deimos in 3D, at true scale
Deimos is the smaller and outer of the two moons of Mars, a lumpy, dusty body barely 12 km across. It is probably a captured asteroid or debris from an ancient impact on Mars.
At a glance
| Diameter | 12.4 km |
|---|---|
| Mass | 1.48 × 10¹⁵ kg |
| Diameter compared with Earth | 0.001 × Earth |
| Size | About 15 × 12 × 11 km |
| Orbits | Mars, every 30.3 hours |
| Discovered | 1877, Asaph Hall |
| Name | Greek for dread |
Good to know
- Its gravity is so weak that a good jump could launch you into space.
- Seen from Mars it looks like a bright star, not a moon.
- Its surface is smoothed by a thick layer of fine dust.
- Next smaller: Halley's Comet · 11.0 km
- Next larger: Neutron star · 22.0 km