* Astronomy

On July 29, 1969, less than a week before closest approach to Mars, 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.
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Mariner 7 made its closest flyby of Mars in 1969