Deimos is the smaller outer moon of Mars (the inner moon is Phobos.) Demios is composed of rock rich in carbonaceous material. Although the surface is noticeably smoother than Phobos it is still cratered. The two largest craters each measure about 3 kilometers in diameter.
The name Deimos (Dread) comes from Book XV of the Iliad. The name was suggested by Henry Madan (1838–1901)