Mariner 7, following Mariner 6's flyby on July 31, has its closest approach at a distance of 3,524 kilometers (2,190 miles). This mission is the first dual mission to a planet.

By chance, both craft fly over cratered regions and miss both the giant northern volcanoes and the equatorial grand canyon that are discovered later. Their approach pictures do, however, show that the dark features on the surface long seen from Earth are not canals, as once interpreted in the 1800s.

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