Phobos and Deimos

The Moons of Mars

Phobos is the largest of the two moons of Mars, discovered by humans in 1877 by Asaph Hall. It is a dark, irregular body that measures 27 x 22 x 19km (17 x 14 x 12 miles) and is thought to be an asteroid caught in the gravity field of Mars.

It has two large craters that humans call Stickney and Hall.

Deimos is the outermost and smallest of the two moons of Mars; like Phobos, it is believed to be an asteroid captured by the gravity of Mars - they both have similar properties in their surface materials to bodies found in the asteroid belt, blackish carbonaceous chondrite or C-Type asteroids.