How many spacecraft have been to Mercury?
Two spacecraft have visited the planet Mercury so far. The first was called Mariner 10. During 1974 and 1975, Mariner 10 flew by Mercury three times and mapped about half of the planet's surface. Mariner 10 also discovered Mercury's thin atmosphere and detected its magnetic field. More recently, Messenger went into orbit around Mercury in 2011, and completed mapping of 100% of Mercury's surface in 2013. BepiColombo is planned for launch in 2015 and planned to enter orbit around Mercury in 2022.