A rocky planet the planets closest to the sunâ€mars, earth, venus, and mercuryâ€are made mostly of rock.The rocky planets all formed in our inner solar system.Their geological history is preserved on …In 1971 mariner 9 entered orbit around mars, being the first spacecraft to orbit any body other than the moon, sun or earth;Following in the same year were the first uncontrolled impact (mars 2) and first …Nasa’s real-time portal for mars exploration, featuring the latest news, images, and discoveries from the red planet.