The MESSENGER mission to Mercury: scienti(c objectives and implementation

Mercury holds answers to several critical questions regarding the formation and evolution of the terrestrial planets. These questions include the origin of Mercury’s anomalously high ratio of metal to silicate and its implications for planetary accretion processes, the nature of Mercury’s geological evolution and interior cooling history, the mechanism of global magnetic (eld generation, the state of Mercury’s core, and the processes controlling volatile species in Mercury’s polar deposits, exosphere, and magnetosphere. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission has been designed to Ay by and orbit Mercury to address all of these key questions. After launch by a Delta 2925H-9.5, two Aybys of Venus, and two Aybys of Mercury, orbit insertion is accomplished at the third Mercury encounter. The instrument payload includes a dual imaging system for wide and narrow (elds-of-view, monochrome and color imaging, and stereo; X-ray and combined gamma-ray and neutron spectrometers for surface chemical mapping; a magnetometer; a laser altimeter; a combined ultraviolet–visible and visible-near-infrared spectrometer to survey bothexosph eric species and surface mineralogy; and an energetic particle and plasma spectrometer to sample charged species in the magnetosphere. During the Aybys of Mercury, regions unexplored by Mariner 10 will be seen for the (rst time, and new data will be gathered on Mercury’s exosphere, magnetosphere, and surface composition. During the orbital phase of the mission, one Earth year in duration, MESSENGER will complete global mapping and the detailed characterization of the exosphere, magnetosphere, surface, and interior. c