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R. L. McNutt, Jr. (APL/JHU), S. C. Solomon (DTM/CIW), MESSENGER Team
Mercury holds answers to several critical questions regarding the formation and evolution of the terrestrial planets. Determining the composition of Mercury, with its anomalously high ratio of metal to silicate, will provide a unique window on the processes by which planetesimals in the primitive solar nebula accreted to form planets. Documenting the global geological history will elucidate the role of terrestrial planet size as a governor of magmatic and tectonic history. Characterizing the magnetic field and the size and state of Mercury’s core will advance our understanding of the energetics and lifetimes of magnetic dynamos in solar system bodies. Determining the volatile species in Mercury's polar deposits, exosphere, and magnetosphere will provide insight into volatile inventories, sources, and sinks in the inner solar system. The MESSENGER mission to fly by and orbit Mercury will accomplish all of these key objectives. After launch by a Delta II 7925H, an Earth flyby, two flybys of Venus, and two flybys of Mercury, orbit insertion is accomplished at the third Mercury encounter. The instrument payload includes a dual imaging system for wide and narrow fields-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 UV-visible and visible-near-infrared spectrometer to survey both exospheric species and surface mineralogy; and an energetic particle and plasma spectrometer to sample charged species in the magnetosphere. During the flybys of Mercury, regions unexplored by Mariner 10 will be seen for the first 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.