Phobos (moon) Phobos (moon) Phobos ( , , ; systematic designation: ) is the innermost and larger 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 and is seven times as massive as the outer moon, Deimos. Phobos is named after the Greek god Phobos, a son of Ares (Mars) and Aphrodite (Venus) and the personification of horror (cf. phobia). Phobos orbits from the Martian surface, closer to its primary body than any other known planetary moon.
Phobos monolith astronaut Buzz Aldrin has spoken about the Phobos monolith and his support for a mission to Phobos. The object appears in Mars Global Surveyor images SPS252603 and SPS255103, dated 1998. The object is unrelated to another monolith located on the surface of Mars, which NASA noted as an example of a common surface feature in that region. Phobos monolith The Phobos monolith is a large rock on the surface of Mars's moon Phobos. It is a boulder about across and tall. A monolith is a geological feature consisting of a single massive piece of rock. Monoliths also occur naturally on