Deimos Moon Facts


Deimos is the smaller of the two moons of Mars. Like its sibling moon Phobos, it has a dusty “regolith” covered surface, and is made of rocky material.

Deimos Size

Deimos Size
Deimos size compared to the Moon

Facts about Deimos

  • Neither Phobos nor Deimos have atmospheres. They are too small, with no volatiles to create an atmosphere, and their gravity too low to retain one.
  • Like Phobos, Deimos has characteristics that make it similar to a C-type asteroid. It is not a spherical moon.
  • Deimos has a much smoother surface than Phobos, although it does have some craters. The two largest are named Swift and Voltaire, after 19th century writers.
  • Deimos has a nearly circular orbit around Mars. It may also have been a captured asteroid, but its orbit would have needed a long time to become circular.
  • An observer looking at Deimos from the surface of Mars would see a small body which at “full moon” would be about as bright as Venus looks from Earth.
  • One theory suggests that both Phobos and Deimos were part of a swarm of smaller objects around early Mars. They may have come to the Red Planet as part of a collision between planetesimals.
  • Deimos has not been formally visited by a spacecraft. However, most of the missions to Mars have also studied this little moon as they imaged and mapped Mars.
  • Missions have been proposed to study both moons of Mars. One is called Phobos and Deimos and Mars Environment (PADME). Another is called OSIRIS-REx 2, which is a followup to OSIRIS-REx, a regolith and surface mission currently in development at NASA.

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