Deimos /ˈdaɪmɒs/ (systematic designation: Mars II) is the smaller and outermost 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, and who is also a son of Ares and Aphrodite and the twin brother of Phobos.

 

Note:   The above text is excerpted from the Wikipedia article Deimos (moon), which has been released under the GNU Free Documentation License.