Global Color View of Mars. - stock photo

June 8, 1998 - Global Color View of Mars. About 1000 Viking Orbiter red- and violet-filter images have been processed to provide global color coverage of Mars at a scale of 1 km/pixel. Individual image frames acquired during a single spacecraft revolution were first processed through radiometric calibration, cosmetic cleanup, geometric control, reprojection, and mosaicing. All of the mosaics are geometrically tied to the Mars Digital Image Mosaic, a black-and-white base map with a scale of 231 m/pixel. Photometric normalization was applied to remove atmospheric effects and normalize the variations in illumination and viewing angles. Finally, these normalized mosaics were combined into global mosaics. Global coverage is about 98% complete in the red-filter mosaic and 95% complete in the violet-filter mosaic. Gaps were filled by interpolation. A green-filter image was synthesized from an average of the red and violet filter data to complete a 3-color set. The Viking Orbiters acquired green-filter images for about half of the Martian surface. The final mosaic has been reprojected into several map projections. The orthographic view shown here is centered at 20 degrees latitude and 60 degrees longitude and is most like the view seen through a telescope. The color balance is close to natural color for the bright reddish regions such as Tharsis and Arabia, but the data have been stretched such that the relatively dark regions appear darker and less reddish than their natural appearance. The color and brightness variations on Mars are related to the composition or physical structure of the surface materials - volcanic lava flows, wind- and water-deposited sedimentary rocks, ice caps. The north polar cap is visible in this projection at the top of the image, the great equatorial canyon system (Valles Marineris) below center, and four huge Tharsis volcanoes at left. Also note heavy impact cratering of the highlands and the younger, less heavily cratered terrains elsewhere.