NASA’s Mariner 2 became the first successful planetary flyby mission in 1962.
Launched on August 27, 1962, Mariner 2 traveled toward Venus. It passed Venus on December 14, 1962, at a distance of about 34,800 kilometers. The spacecraft then continued transmitting data, proving that an interplanetary mission could operate successfully beyond Earth’s orbit.
Mariner 2 measured Venus’s temperature, atmosphere, and magnetic environment. Its observations showed that Venus was extremely hot, challenging earlier ideas that the planet might have Earth-like conditions. The mission also detected the solar wind, helping establish that this stream of charged particles continuously flows from the Sun.
Several earlier planetary attempts had failed, including the Soviet Venera 1 mission and NASA’s Mariner 1 launch failure. Mariner 4 later performed the first successful flyby of Mars in 1965, so it was not the first planetary flyby overall.