Mariner 2NASA’s unmanned Mariner 2 probe is the first unmanned spacecraft to successfully reach and take measuresments of another planet in the solar system. Passing by Venus at a distance of 25,000 miles, Mariner 2 detects a cool atmosphere with a blistering hot surface underneath it – quickly dispelling any hopes of finding life there. Mariner 2 isn’t equipped with any cameras, which is just as well: unless any cameras had ultraviolet filters, they would have seen nothing but featureless clouds at Venus. Mariner 2 continues on into a solar orbit, shutting down early in 1963.