The Moons of Mars

Deimos named after a son of Ares (Mars) and Aphrodite (Venus) was discovered on August 12, 1877, by American astronomer Asaph Hall. It is compsed of carbon rich rock and ice, has no atmosphere, is cratered though smoother than Phobos, has a diameter of 12 kilometers and orbits at just over 20,000 kilometers above its primary. Its most prominent surface features are two large craters named Voltaire and Swift

Phobos the larger of Mars' two moons and also named after a son of Ares (Mars) and Aphrodite (Venus) was discovered on August 18, 1877, also by Asaph Hall. Like its companion it is composed of carbon rich rock and ice and has no atmosphere (although the Soviet probe Phobus 2 detected outgassing) and is covered in a thick layer of dust, rock and debris called regolith. [1] It has a diameter of 22 kilometers and orbits less than 6,000 kilometers above Mars' surface (closest to its primary of any satellite in the Solar System). Its most prominent surface feature is Stickney crater.

Unlike Earth's moon which is a true moon, Phobos and Deimos are probably captured asteroids and should more properly be referred to as minor moons.

In Greek "Deimos" means panic while "Phobus" means fear.

[1] Russia’s Phobos-Grunt (“grunt” means “soil” in Russian) spacecraft which lifted off from a launch site in Kazakhstan November 9, 2011, (8 November UTC) and originally headed for a Martian moon, fell back from space Sunday, January 15, after being stuck in Earth orbit due to an engine misfire. The 14.9 ton (13.5 metric ton) spacecraft carrying fuel, a Chinese orbiter and a Martian moon lander was to have placed China’s Firefly spacecraft into Mars orbit, landed on the diminutive moon Phobos retrieved soil samples and returned to Earth.

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