Deimos is the smaller of Mars's two moons, about 15 km long. You could walk across it in an afternoon.
Its name means dread. It and Phobos were both found in August 1877 by the American astronomer Asaph Hall.
Thick dust smooths its craters over, so it looks softer than lumpy Phobos.
From the surface of Mars, Deimos is so small and far that it looks like a bright star, not a moon.
Scientists still argue about where Mars's moons came from: captured asteroids, or rubble from a giant crash on Mars.
- Width
- 12 km
- Goes round Mars
- every 30 hours
- One day
- The same: it always shows Mars one face
- Temperature
- about −40 °C
- 70 kg on Earth weighs
- 21 grams here
