Mars has two moons, Phobos and Deimos. Both are small and irregularly shaped and may be asteroids. Interestingly, Phobos orbits Mars at a distance of only about 5,500 miles away from its center, the closest any moon its planet. In fact, if a person were to stand on Phobos and look Mars, Mars would look 6,400 times larger than the full moon appears from Earth - taking up almost a quarter of the celestial hemisphere. Because Phobos has a low orbit, scientists believe it will crash into Mars or break up into pieces, possibly rings around the planet.