Deimos

Mars moon · space · outer solar system

Mars's tiny moon. Deimos is the smaller of Mars's two moons and measures only about 6.2 kilometers across, roughly the size of a city. It orbits so far from Mars that it takes 30.3 hours to go around the planet, which is longer than Mars takes to spin on its axis.

Named after fear. Deimos gets its name from the ancient Greek god of dread and terror. Its sister moon, Phobos, is named after fear, so Mars has two moons with scary mythological names.

Very distant orbit. Deimos orbits about 23,460 kilometers from Mars, making it much farther away than Phobos. Because it's so far out, Deimos moves slowly and takes a long time to complete one orbit.

A natural satellite. Deimos is a natural moon made of rock, not an artificial satellite humans built. Scientists think it might be a captured asteroid that got pulled into Mars's gravity long ago.