Mars has two moons, named Phobos and Deimos. Both moons are small and irregularly shaped, and are thought to be either captured asteroids or debris from the early solar system formation
- Phobos is the larger moon, about 22.2 km (13.8 miles) across. It orbits very close to Mars-about 6,000 km (3,700 miles) above the surface-and completes three orbits around Mars every Earth day. Phobos is gradually spiraling inward and is expected to either crash into Mars or break up into a ring in about 50 million years
- Deimos is smaller, approximately 12.6 km (7.8 miles) in diameter. It orbits farther away from Mars, taking about 30 hours to complete one orbit
Both moons were discovered in August 1877 by American astronomer Asaph Hall and are named after the mythological twin sons of Ares (Mars), representing fear (Phobos) and dread (Deimos)
