from wiki: Deimos (systematic designation: Mars II) is the smaller and outermost of the two natural satellites of the planet Mars. Deimos has a mean radius of 6.2 km and takes 30.3 hours to orbit Mars. Deimos is 23,460 km from Mars, much further than Mars’s other moon, Phobos. It is named for Deimos, who in Greek mythology is the twin brother of Phobos, and personifies terror.