Discovery of Deimos

Deimos is the smaller and outer of Mars's two moons, discovered by the American astronomer Asaph Hall at the United States Naval Observatory in Washington in August 1877. Hall found it only days before its companion Phobos, after a deliberate search made while Mars was unusually close to Earth. Deimos is a small, irregular body only a few kilometres across, with a relatively smooth surface covered by loose dust, and it takes about thirty hours to orbit Mars. The two moons were named after the attendants of the Greek war god Ares, whose Roman counterpart is Mars, with Deimos meaning dread. Scientists still debate whether they are captured asteroids or were formed from debris thrown up by an ancient impact.

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