Mariner-7 far-encounter pictures 38, 47 and 57 (left to right) made respectively from distances of 716,000 , 630,000 and 535,000 miles. Picture 38 features the dark solis lacus , half way from the centre to the bottom. Known the "eye of mars" it has been identified in some of the earliest drawings of the planet. Picture 47 shows a wealth of detailed bright structure around the huge crater Nix Olympia . The region is observed to change its brightness but not its structure from day to day . In picture 57 the irregualr northern border of the south polar cap can be distinguished . It is now spring in the southern hemisphere and the cap border is slowly shrinking in size 4 August 1969