Mariner 3/4

Mariner-Mars 1964

Mission Profile

Mariner 3 and 4 were twin NASA spacecraft designed to conduct the first flyby of Mars, launched in November 1964 aboard Atlas LV-3 Agena-B rockets. Mariner 3 failed when its fairing refused to open after launch, but Mariner 4 succeeded spectacularly, flying past Mars on 14 July 1965 and returning 21 close-up photographs of the Martian surface. These images revealed a heavily cratered, Moon-like surface far different from the canals imagined by 19th century astronomers, fundamentally reshaping scientific understanding of Mars. Mariner 4 also measured the thin Martian atmosphere, confirming surface pressure of only 4-7 millibars, eliminating hope for surface liquid water and significantly dampening expectations for Martian life.