Goals: Identical to Mariner 6, which was launched 31 days earlier, Mariner 7 had the same goal: to study the surface and atmosphere of Mars during a close flyby.
Accomplishments: The Mariner 7 mission benefited from its reprogrammable command system. When scientists, intrigued by Mariner 6's pictures of the Martian south pole, asked that Mariner 7 take extra pictures of that area, controllers were able to comply. The spacecraft took 93 far- and 33 near-encounter images, showing heavily cratered terrain very similar to images recorded by Mariner 6. The south polar cap was identified as mostly carbon dioxide.