<Tr> <Th> Temperature </Th> <Td> ≈ 233 K </Td> </Tr> <Tr> <Th> Apparent magnitude </Th> <Td> 11.8 </Td> </Tr> <P> Phobos (/ ˈfoʊbəs / FOH - bəs or / ˈfoʊbɒs / FOH - bos, from the Greek Φόβος .) (systematic designation: Mars I) 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 . </P> <P> Phobos is a small, irregularly shaped object with a mean radius of 11 km (7 mi), 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). </P>

Phobos and demos are natural satellite of which planet
find me the text answering this question