This color picture of Mars was made from three frames shuttered nine seconds apart by the Viking 1 Orbiter on June 18. Each of the three pictures was taken through a different filter - red, green and violet. Color reconstruction was done at the Image Processing Facility of the U. S. Geological Survey in Flagstaff, Arizona. Just below the center of the picture and near the morning terminator is the large impact basin Argyre. Interior of the basin is bright, suggesting ground frost or a ground haze. Bright area south of Argyre probably is an area of discontinuous frost cover near the south pole. The pole, itself, is in the dark at lower left. North of Argyre, the "Grand Canyon" of Mars, called Vallis Marineris, can be seen near the terminator. Markings elsewhere on the planet are mostly due to differences in brightness; however, color differences are present, suggesting compositional differences. Area at the top is the eastern side of the Tharsis volcanic region and is bright because of cloud activity. Photograph and caption published in Winds of Change, 75th Anniversary NASA publication (page 107), by James Schultz.
