D eimos (panic) is a moon of Mars and was named after an attendant of the Roman war god Mars. It was discovered by Asaph Hall in 1877. Deimos is a dark body that appears to be composed of C-type surface materials. It is similar to the C-type (blackish carbonaceous chondrite) asteroids that exist in the outer asteroid belt. Some scientists speculate that Deimos and Phobos (the other martian moon), are captured asteroids; however, other scientists present arguments counter to this theory. Both Deimos and Phobos are saturated with craters. Deimos has a smoother appearance caused by partial filling of some of its craters.