Mariner 10 was the last
spacecraft of the
Mariner program, launched on
November 3,
1973; this was an
unmanned space mission (Mariners 11 and 12 were redesignated as
Voyager 1 and
Voyager 2). Mariner 10 was launched ~2
years after
Mariner 9 and its mission was to
explore Mercury and
Venus. Mariner 10 made use of a "
gravitational slingshot", using Venus to bend its flight path. Using a near-
ultraviolet filter, it produced
photographs of the Venusian
chevron clouds[?] and performed other
atmospheric studies. On
March 29 and
September 21, 1974, and
March 16,
1975; Mariner 10 passed by Mercury and was able to
map 40-45% of the planet. No spacecraft has since returned to Mercury.