Mariner 2 became the first spacecraft to conduct a successful planetary flyby when it passed Venus in 1962.
NASA launched Mariner 2 on 27 August 1962. After travelling for more than three months, it flew past Venus on 14 December at a distance of about 34,800 kilometres. Its instruments measured Venus’s temperature and detected the solar wind beyond Earth’s orbit.
The mission showed that interplanetary spacecraft could operate reliably over great distances and transmit scientific data back to Earth. Mariner 2 also provided evidence that Venus was extremely hot, challenging some earlier ideas that its atmosphere might resemble Earth’s.
Mariner 1 was intended to perform the same mission but was lost shortly after launch because of a guidance-related failure. Mariner 4, launched later, became the first spacecraft to return close-up images of Mars.