Phobos (moon)

Phobos (systematic designation: Mars I) is the larger and innermost of the two natural satellites of Mars, the other being Deimos. Both moons were discovered in 1877 by American astronomer Asaph Hall.

Phobos is a small, irregularly shaped object with a mean radius of 11 km (7 mi), and is seven times more massive than Deimos, Mars's outer moon. Phobos is named after the Greek god Phobos, a son of Ares (Mars) and Aphrodite (Venus) which was the personification of Horror. The name "Phobos" is pronounced /ˈfoʊbəs/ FOH-bəs or /ˈfoʊbɒs/ FOH-bos, or like the Greek Φόβος.