Deimos

Mars's smallest, smoothest moon

Deimos is Mars's tiny moon, about the size of a city neighbourhood. From Mars it looks like a very bright star. Deimos is covered in a thick blanket of dust, which makes it look smooth and soft. It is slowly drifting away from Mars.

Deimos is an irregular body 15×12×11 km across, orbiting 23,460 km from Mars every 30.3 hours. Unlike Phobos, its craters are filled with thick regolith (dust), giving it a smoother look. Its two largest craters are named Swift and Voltaire, after writers who 'predicted' two Martian moons long before they were discovered in 1877. Both moons were found by Asaph Hall. Deimos's orbit is slowly widening, and it will eventually escape Mars.

Fun facts

• Deimos means 'terror' — with Phobos, the two sons of the god of war.
• From Deimos, Mars fills a third of the sky!
• Deimos hangs in the Martian sky for 2.7 days — that's how slowly it moves.