Phobos is the larger and closer of the two natural satellites of Mars

Mars

Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...

. Both moons were discovered in 1877. With a mean radius of 11.1 km (6.9 mi), Phobos is 7.24 times as massive as Deimos. It is named after the Greek god

Greek mythology

Greek mythology is the body of myths and legends belonging to the ancient Greeks, concerning their gods and heroes, the nature of the world, and the origins and significance of their own cult and ritual practices. They were a part of religion in ancient Greece...

 Phobos

Phobos (mythology)

Phobos is the personification of horror in Greek mythology. He is the offspring of Ares and Aphrodite. He was known for accompanying Ares into battle along with his brother, Deimos, the goddess Enyo, and his father’s attendants. Timor is his Roman equivalent...

 (which means "fear"), a son of Ares

Ares

Ares is the Greek god of war. He is one of the Twelve Olympians, and the son of Zeus and Hera. In Greek literature, he often represents the physical or violent aspect of war, in contrast to the armored Athena, whose functions as a goddess of intelligence include military strategy and...

 (Mars).

A small, irregularly shaped object, Phobos orbits about 9377 km (5,826.6 mi) from the center of Mars, closer to its primary

Primary (astronomy)

A primary is the main physical body of a gravitationally-bound, multi-object system. This body contributes most of the mass of that system and will generally be located near its center of mass....

 than any other known planetary moon.