Data collected from Mariner 4's flyby on a modern map
A Mars flyby is when a spacecraft passes near the planet Mars, but does not enter orbit or land on it. Unmanned (no humans on board) space probes have used this method to collect data on Mars and other worlds. A spacecraft that is built for a flyby is also known as a "flyby bus" or "flyby spacecraft".
Two Mars flyby attempts were made in 1960 under Mars 1M (Mars 1960A and Mars 1960B).
The third attempt at a Mars flyby was the Soviet Mars 2MV-4 No.1, also called Mars 1962A or Sputnik 22, which launched in 1962 as part of the Mars program. but it was destroyed in low Earth orbit due to rocket failure.
Mars 1 also launched in 1962 but communications failed before it reached Mars.
Mars 4 achieved a flyby in 1974 and detected a night-side ionosphere, although by that time Mars was already orbited by other spacecraft.
Mars 6 and 7 were Mars landers carried by flyby buses.
References
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Page 15-16 in Chapter 3 of David S. F. Portree's Humans to Mars: Fifty Years of Mission Planning, 1950 - 2000, NASA Monographs in Aerospace History Series, Number 21, February 2001. Available as NASA SP-2001-4521.