Mars is in the Solar System.
Mars . Mars is the site of Olympus Mons , the largest volcano and second-highest known mountain in the Solar System , and of Valles Marineris , one of the largest canyons in the Solar System . Mars , the fourth planet in the solar system , has been featured in the Doctor Who fictional universe on a number of occasions . Solar System . The four smaller inner planets , Mercury , Venus , Earth and Mars , are terrestrial planets , being primarily composed of rock and metal . The asteroid belt , which lies between the orbits of Mars and Jupiter , mostly contains objects composed , like the terrestrial planets , of rock and metal .