Mars has two small moons, Deimos and Phobos . The names are taken from the Greek for Dread (Deimos) and Fear (Phobos). They were discovered by Asaph Hall in 1877.
Phobos is the larger of the two moons (barely larger than 16 miles at its biggest point) and orbits Mars once every 11 hours and 6 minutes. Both moons are odd-shaped and very small. Both Phobos and Deimos were most-likely captured asteroids or the result of a collision with Mars. As the images show, both moons have craters. Neither moon has an atmosphere.