Mars has two very small elliptical-shaped moons, Deimos and Phobos. They were discovered in August 1877 by the American astronomer Asaph Hall (1829–1907) of the U.S. Naval Observatory in Washington, DC.The inner moon, Phobos, is 27 km long, and it revolves around the planet in 7.6 hours. Phobos is closer to its planet than any other moon in the solar system, orbiting Mars with an orbital radius of only 9378 km. The outer moon, Deimos, is 15 km long and it circles the planet in 30.35 hours. How far away from Mars’s center is Deimos?