As part of NASA's wider Mariner program, Mariner 6 and Mariner 7 (Mariner Mars 69A and Mariner Mars 69B) completed the first dual mission to Mars in 1969. Mariner 6 was launched from Launch Complex 36B at Cape Kennedy and Mariner 7 from Launch Complex 36A at Cape Kennedy. The craft flew over the equator and south polar regions, analyzing the atmosphere and the surface with remote sensors, and recording and relaying hundreds of pictures. The mission's goals were to study the surface and atmosphere of Mars during close flybys, in order to establish the basis for future investigations, particularly those relevant to the search for extraterrestrial life, and to demonstrate and develop technologies required for future Mars missions. Mariner 6 also had the objective of providing experience and data which would be useful in programming the Mariner 7 encounter 5 days later.

On July 29, 1969, less than a week before closest approach, NASA Jet Propulsion Laboratory lost contact with Mariner 7. The center regained the signal via the backup low-gain antenna and were able to start using the high gain antenna again shortly after Mariner 6's close encounter. It was thought leaking gases from a battery (which later failed) had caused the anomaly. Based on the observations made by Mariner 6, Mariner 7 was reprogrammed in flight to take further observations of areas of interest and actually returned more pictures than Mariner 6, despite the battery's failure.

By chance, both flew over cratered regions and missed both the giant northern volcanoes and the equatorial grand canyon discovered later. Their approach pictures did, however, photograph about 20 percent of the planet's surface, showing the dark features long seen from Earth, but none of the canals mistakenly observed by ground-based astronomers. In total 198 photos were taken and transmitted back to Earth, adding more detail than the earlier mission, Mariner 4. Both craft also studied the atmosphere of Mars.

Closest approach for Mariner 6 occurred July 31, 1969, at 05:19:07 UT at a distance of 3,431 kilometres (2,132 mi) above the martian surface. Closest approach for Mariner 7 occurred August 5, 1969 at 05:00:49 UT at a distance of 3,430 kilometres (2,130 mi) above the martian surface.

The ultraviolet spectrometer onboard Mariners 6 and 7 was constructed by the Laboratory for Atmospheric and Space Physics.

The engineering model of Mariners 6 and 7 still exists, and is owned by the Jet Propulsion Laboratory. It is currently on loan to the Laboratory for Atmospheric and Space Physics, and is on display in the lab's lobby.

The craft are now defunct in heliocentric orbits.

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