Developed together, the twin Mariner 1 and 2 spacecraft were based on the Ranger lunar probe and planned for a joint mission to our closest neighboring planet. The probes featured seven instruments for studying Venus’ atmosphere, temperature, and magnetic field. On July 22, 1962, Mariner 1 launched, but the spacecraft was destroyed only minutes into its first flight when its rocket went off course. Mariner 2’s launch on Aug. 27 was successful, though, and it set off for Venus. (En route, it confirmed the existence of the solar wind proposed by Eugene Parker in 1958.)
Finally, after a journey of 110 days and 182 million miles (293 million kilometers), the craft arrived at Venus. On Dec. 14, 1962, it executed the first successful interplanetary mission, flying by at about 21,000 miles (34,000 km) and scanning the planet for 42 minutes. Among other data, Mariner 2 showed that Venus was extremely hot, with the heat coming from its surface, though its atmosphere remained cold. Mariner 2 also revealed that the venusian atmosphere was very dense and pressurized far beyond Earth’s. These conditions, as well as the lack of a magnetic field, showed that Venus was inhospitable.
