View of the surface of the planet Mars, 1976.
© National Aeronautics & Space Administration / Science & Society
Very little surface detail can be seen in this photograph taken by the Viking 1 Orbiter. Two Viking spacecraft were launched towards Mars by NASA 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. No evidence of life was found, but more recent studies of the Martian landscape suggest that in the past abundant surface water may have been present, which could have enabled life to exist. Today Mars has a very thin atmosphere, mainly of carbon dioxide, and no liquid surface water appears to exist. The planet's red colour is due to the presence of large quantities of iron oxide on its surface.