Geophysical investigations of earth, moon and mercury

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This proposal comprises studies of the magnetic fields of Mercury, the Moon and Earth, along with studies of Mercury's crust and lithosphere. These topics provide information on the interior structure and evolution of inner solar system planets and moons. Investigations of Mercury will use data from NASA's MESSENGER mission, from 3 flybys in 2008 and 2009, and from orbit in 2011-2012. The studies proposed will allow discrimination of crustal and core sources for the magnetic field, and evaluation of proposed core dynamo models. The combined use of topography, gravity, and image data will allow studies of the thickness of Mercury's crust and lithosphere over time, and investigations of the evolution of large impact basins. Satellite observations of the lunar magnetic field, along with strong magnetizations observed in some Apollo samples indicate the presence of remanent magnetization in the lunar crust; however the origin and timing of the magnetizing field is not understood. Both a core dynamo and impact (shock) processes have been suggested. Proposed studies aim to understand whether the Moon had a core dynamo and if so when. If shock has played a major role in the acquisition of crustal remanence on the Moon, why is this record so different from at Mars, and what implications does this have for Mercury? The structure and evolution of Earth's magnetic field is key to understanding the geodynamo and Earth's deep interior, but many aspects of it remain poorly documented. Proposed studies will map the changes in strength and direction of the field over the past 2.5 Myr, by integrating different types of rock magnetic records, and developing global magnetic field models.