Trajectory of the Mariner 10 probe. Computer graphic of the flight path of the unmanned Mariner 10 probe sent by NASA to Mercury. It launched from Earth (upper right) in November 1974 and passed close to Venus (centre left) in February 1974. This adjusted its orbit so that it flew past Mercury in March 1974, September 1974, and March 1975. Mercury is less than 60 million kilometres from the Sun. Mariner 10 mapped nearly half of Mercury's surface and measured its temperatures in the day (187 degrees Celsius) and at night (-183 degrees Celsius). Contact with Mariner 10 ended on 24 March 1975. The next mission to Mercury, the MESSENGER probe, launched in August 2004 and will arrive in 2011.