The Exploration of Mercury by Spacecraft

The planet Mercury is sufficiently close to the Sun to pose a major challenge to spacecraft exploration. The Mariner 10 spacecraft flew by Mercury three times in 1974-1975 but viewed less than half of the surface. With the three flybys of Mercury by the MESSENGER spacecraft in 2008-2009 and the insertion of that probe into orbit about Mercury in 2011, our understanding of the innermost planet substantially improved. In its four years of orbital operations, MESSENGER revealed a world more geologically complex and compositionally distinctive, with a more dynamic magnetosphere and more diverse exosphere-surface interactions, than expected. With the launch of the BepiColombo dual-orbiter mission, the scientific understanding of the innermost planet has moved another major step forward.