Valles Marineris, Viking 1 image. This massive system of canyons near the equator on Mars was named after the Mariner 9 mission that led to its discovery in 1971. The entire canyon system is some 4000 kilometres long, 200 kilometres wide and up to 7 kilometres deep, dwarfing similar canyons on Earth. Viking 1 and its twin probe Viking 2 collected about 52,000 images of Mars. Each Viking also had a lander unit which relayed back information from the Martian surface.