Deimos is one of the two moons of MARS, the other being Phobos. It is named after the Greek god of terror, Deimos, and is the smaller of the two moons. It orbits MARS at a distance of about 23, 500 km and has an orbital period of 30.3 hours. Deimos is also the name of the Greek god of war, ARES, who is the son of Zeus and Hera. The MOON is believed to have been formed from the debris of a large asteroid that collided with MARS billions of years ago.