This crescent phase picture of Mars was taken by Viking 2 on August 5 from a distance of about 400,000  kilometers (250,000 miles) as it was approaching the planet for its  orbit insertion  maneuver.  Viking 2 went into orbit around the  planet at 5:30 A.M., PDT today. The view is of the  morning side. Toward the top of the picture, the four dark  spots are the huge volcanoes of the Tharsis region.  They appear dark partly because clouds and haze cover this  region at this time of day, and the volcanoes stand higher  than the clouds. In the bottom part of the picture, at the tip of  the crescent, is  a bright circular feature, the large impact basin, Argyre.  This basin shows up brightly because its floor is covered with frost.
NASA (digital w/colortable by Jcpag2010)
1976-08-07
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