Mariner 6The unmanned NASA/JPL space probe Mariner 6 makes its closest flyby of planet Mars, coming as close as just over 2100 miles from the Martian surface. While measuring the composition of the Martian atmosphere and trying to analyze its surface from space, Mariner 6 passes over densely cratered terrain, not spotting the huge canyons and volcanoes that will later become synonymous with Mars. Mariner 6’s identical twin, Mariner 7, is just days behind it, and ground controllers rewrite Mariner 7’s flight plan to get closer looks at surface features first spotted by Mariner 6.