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Mars has two moon, Phobos and Deimos. They were discovered by the American astronomer Asaph Hall (1829-1907) in 1877.
They are both small moons; Phobos is 13.8 miles (22.2 km) across and Deimos is only 7.8 miles (12.6 km) across.
These moons are heavily-cratered and are composed of rock and iron. They are probably former asteroids that were captured by Mars’ gravitational field. They have no atmosphere.
Phobos
Phobos (meaning “fear”) is the larger of the two tiny moons of Mars. It is only 13.8 miles (22.2 km) across and has a mass of 1.08 x 1016. It orbits Mars at a mean distance of 5,600 miles (9,000 km). Its major feature is a large crater, named Stickney (Hall’s wife’s maiden name), which is 6.2 miles (10 km) wide. Phobos was discovered by astronomer Asaph Hall in 1877.
Deimos
Deimos (meaning “terror”) is the smaller of the two tiny moons of Mars. Deimos is only 7.8 miles (12.6 km) across and has a mass of 1.80 x 1015. It orbits at a mean distance of 14,300 miles (23,000 km) from Mars. It was discovered by A. Hall in 1877.