Mars taken by Mariner 7 showing the planet with unusual clarity although it is nearly one million miles distance from camera . The south polar gap , the concentration of extensive dark regions in the southern hemsiphere , and the much brighter " desert " area in the northern hemisphere are apparent . The sharpness and irregularity of contacts between the dark and light areas are shown with unusual clarity . Dark spot in the bright area to the east is a reference mark in the camers system , not a feature of Mars. 3 August 1969