Deimos

In 1877, Hall used it to discover Mars 'two moons, Phobos and Phobos, which were named "Phobos" and "Deimos" respectively, which in Greek mythology were the names of the two sons of the war god. In addition, he also measured Saturn's rotation period.

Phobos (pronounced "FOHbus" in English) is shaped like a potato and orbits Mars three times a day, with an average distance of about 9378 kilometers from Mars. It is the larger of Mars 'two moons and the closer to Mars. The distance between Phobos and Mars is also the shortest among all satellites in the solar system and their main star, only 6000 kilometers from the surface of Mars. It is also one of the smallest moons in the solar system.

Deimos (pronounced "DEEmos" in English) is the smaller and farther of the two moons of Mars and the smallest moon in the solar system. The orbit is 23,459 kilometers away from Mars, the satellite has a diameter of 12.6 kilometers (15x12.2x11) and a mass of 1.8e15 kilograms.