[1] Mariner 9 –
Gigantic volcanic mountain on Mars – called Nix Olympica – was photographed by Mariner 9 in late January as the great Martian dust storm subsided. The clearing atmosphere reveals a mountain 500 kilometres (310 miles) across at the base. Steep cliffs drop off from the mountain flanks to a surrounding great plain. The main crater at the summit, a complex multiple volcanic vent, is 65 kilometres (40 miles) in diameter. The mountain is more than twice as broad as the most massive volcanic pile on Earth. (The mountain that forms the Hawaiian Islands is 224 kilometres (140 miles) across and rises nine kilometres (30,000 feet) from the floor of the Pacific to the summit crater, Mauna Loa.) Pressure mapping by Mariner 9’s ultraviolet spectrometer indicates a six-kilometre elevation just part way up the Nix Olympica slope. Continued ultraviolet and infrared measurements may show that the summit crater stands as high as Mauna Loa.
From NASA caption.

[2] Viking 1-10 - One of two television cameras aboard the Viking 1 Orbiter took this picture of an “island” in a channel complex in Mars’ Chryse region. The picture, which covers an area of about 2000 square kilometres (775 square miles), was taken June 22 during the first photo-recommaissance of the prime landing site for Viking 1. The “tail” of the island may have been shaped by flowing water in Mars’ geological past. The crater rim materials also have been etched out by erosion. The channel floor is very rough at the limit of resolution of the picture. Resolution is about 100 metres (300 feet). The picture was taken from a range of 1631 kilometres (1012 miles).
From NASA caption.

[3] The three high resolution fames at upper left, upper right, and lower right were acquired by Mariner 9 on November 19, November 28, and December 1, respectively. The same local area is viewed in each case, but from somewhat different directions, and is indicated with a dark arrow on the accompanying low resolution view. The location of the South Pole of Mars, and the direction of the prime meridian, are shown in white. In the high resolution frames, the maximum dimension corresponds to approximately 400 kilometers (250 miles) on the Martian surface. The low resolution view is printed at 10 times greater scale. At most, only an inch or so of the carbon dioxide frost composing the cap could be expected to have sublimated in such a brief time. Uniform disappearance of thin frost over such a large area indicates this portion of Mars is exceedingly smooth. Underlying low relief or distinctive character appears to be emerging in the bend of the sinuous dark band.
From NASA caption.

[4] This dramatic view of the entire south polar cap of Mars was obtained by Mariner 9 during its fifth orbit of the planet. The larger of the two major remnants is laced with fine, dark, frost-free markings reflecting a topographic pattern apparently unique to this area of Mars. The cap – about 200 miles in diameter – is centred near 85oS, 30oW and the geographic pole (90oS), which is not covered by frost at this season, is at lower right in the mosaic. The overlapping wide-angle pictures were taken from south to north (lower left to upper right).
From NASA caption.