The Viking lander view of Mars

In July 1976, the lander from NASA's Viking 1 probe set down on the western slopes of Chryse Planitia. It soon began its programmed search for Martian micro-organisms and sent back incredible colour panoramas of its surroundings. Scientists learned that the Mars sky was pinkish in colour, not dark blue as they originally thought. The sky is pink due to sunlight reflecting off the reddish dust particles in the thin atmosphere. The lander set down among a field of red sand and boulders stretching out as far as its cameras could image.