Mars is the fourth planet of our solar system. It has two moons named as Phobos and Deimos. Phobos is the closer and larger to mars and Deimos is smaller one. Both moons kept on orbiting the Mars. Phobos moon was discovered on 18 August, 1877 by Asaph Hall, an American astronomer. It was discovered at the United States Naval Observatory in Washington, D.C. Deimos moon was also discovered by Asaph Hall III on 12 August, 1877.