Moon of Mars · Updated May 2026
Deimos.
Deimos is the smaller and outer of Mars's two moons, just 12 km across at its longest dimension. It orbits Mars at 23,458 km in 30 hours and 18 minutes — the slowest of any moon in the inner solar system. Its surface is unusually smooth for such a small body, with small craters partially filled in by regolith.
View Mars system in 3D →Key facts
Deimos is so small that from the Martian surface it would look like a brilliant star, not a disc.
About Deimos
Like Phobos, almost certainly a captured asteroid. Deimos and Phobos together account for far less mass than would be expected if either had formed in situ from a Martian impact, though that hypothesis remains debated. Both moons are tidally locked.
How to view Deimos in 3D
Deimos orbits Mars in real time inside the interactive viewer. Open the parent body to see the orbital geometry, or use the object browser to fly directly to the moon and observe its rotation, surface, and orbit.
Open the Mars system →Sources & methodology
Numbers cross-referenced with the sources below; updated May 2026.