Candor and Ophir Chasmata . ... Credit Copyright: Viking Project , NASA Explanation: First imaged by the Mariner 9 spacecraft, Valles Marineris , the grand canyon of Mars, is a system of enormous depressions called chasmata that stretch some 4,000 kilometers along the Martian equator. Looking north over the canyon's central regions , Candor chasma lies in the foreground of this spectacular view with the steep walls of Ophir chasma near the top. ... NASA Official: Jay Norris. ...