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Friday, July 21, 2017
Mars 4, Soviet probe, launched 1973
The Soviets launched the Mars 4 probe on July 21, 1973 to orbit the Red Planet. Shortly before it reached Mars, two of its on-board computers failed and it passed within 2000km of the Martian surface on February 10, 1974. It did send back some information, but little of it was useful.