Deimos is the smaller and outer of the two natural satellites of Mars, the other being Phobos. Deimos has a mean radius of 6.2 km (3.9 mi) and takes 30.3 hours to orbit Mars. Deimos is 23,460 km (14,580 mi) from Mars, much farther than Mars's other moon, Phobos. It is named after Deimos, the Ancient Greek god and personification of dread and terror.
Deimos, captured by the Mars Reconnaissance Orbiter in enhanced color
Asaph Hall III, discoverer of Deimos
Deimos transits the Sun – as viewed by the Mars rover Opportunity (4 March 2004)
Deimos and Phobos as seen from Mars, compared to the Moon as seen from Earth (in angular sizes)
The two moons of Mars are Phobos and Deimos. They are irregular in shape. Both were discovered by American astronomer Asaph Hall in August 1877 and are named after the Greek mythological twin characters Phobos and Deimos who accompanied their father Ares into battle. Ares, the god of war, was known to the Romans as Mars.
Enhanced color image of Phobos (MRO, 23 March 2008)
Enhanced color image of Deimos (MRO, 21 February 2009)
Asaph Hall III, discoverer of Phobos and Deimos
Apparent sizes of the moons of Mars, Deimos and Phobos, and the Moon as viewed from the surface of their respective planets (Mars' moons imaged by the Curiosity rover, 1 August 2013)
