premise: Mars is the site of Valles Marineris, one of the largest canyons in the Solar System.
hypothesis: 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 . Valles Marineris ( Latin for Mariner Valleys , named after the Mariner 9 Mars orbiter of 1971 -- 72 which discovered it ) is a system of canyons that runs along the Martian surface east of the Tharsis region . At more than 4000 km long , 200 km wide and up to 7 km deep , Valles Marineris is one of the largest canyons of the Solar System , surpassed in length only by the rift valleys of Earth .