Mercury is the first planet from the Sun. It is a rocky planet with a trace atmosphere. While it is the smallest and least massive planet of the Solar System, its surface gravity is slightly higher than that of Mars. The surface of Mercury is similar to Earth's Moon, heavily cratered, with expansive rupes system, generated from thrust faults, and bright ray systems, formed by ejecta. Its largest crater, Caloris Planitia, has a diameter of 1,550km which is about one-third the planet dm of 4,880km