This view was taken by one of the Viking Orbiters. The canyon is some 4000 kilometres long and over 6 kilometres deep in places. Two Viking spacecraft were launched towards Mars in 1975, each carrying a lander spacecraft and an orbiter. Both succesfully landed their probes on Mars to study the Martian environment, soil constituents and to search for simple life forms - none were found.
© National Aeronautics & Space Administration / Science & Society