For GIF formatted image files, the color variations have been enhanced by a factor of two, and the large-scale brightness variations (mostly due to sun-angle variations) have been normalized by large-scale filtering.
The large bright colored area, located in the upper left area of the image is known as Arabia. The dark area to the right of Arabia, called Syrtis Major Planus, is a low-relief volcanic shield of probable basaltic composition. Bright white areas to the south, including the Hellas impact basin at extreme lower right, are covered by carbon dioxide frost. Regions to the west and south of Syrtis Major are heavily cratered and relatively old. The dark feature coming around the western horizon is known as Sinus Sabaeus. Image Processing by Jody Swann/Tammy Becker/Alfred McEwen, using the PICS (Planetary Image Cartography System) image processing system developed at the U.S. Geological Survey in Flagstaff, Arizona.
