Moon of Mars
Deimos
Mars's small outer moon, taking just over a Martian day per orbit.
Deimos circles Mars every 30.3 hours on a nearly perfect circle, only a few hours longer than a Martian day. That close match means it drifts very slowly across the Martian sky. Like Phobos, it keeps one face toward Mars.
How it moves
- Deimos orbits Mars every 1.26244 days (about 30.3 hours), only slightly longer than a Martian day.
- Its orbit is almost perfectly circular, with an eccentricity of 0.0005.
- It orbits about two and a half times farther from Mars than Phobos does.
- Its rotation is synchronous, keeping the same face toward Mars.
Facts
- Mean radius
- 6.2 km
- Mass
- 2.400e+15 kg
- Rotation period
- 30.299 hours
- Orbital period
- 1.262 days
- Average orbital distance
- 23,459 km
- Eccentricity
- 0.0005
- Discovered
- August 11, 1877, by Asaph Hall
Dust knocked off Deimos by impacts stays in orbit near its path and settles back onto its surface.
Sources: nssdc.gsfc.nasa.gov, ssd.jpl.nasa.gov, planetarynames.wr.usgs.gov