Magnetic Field Investigations of Mars and Mercury

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The proposed research program aims to understand the magnetic field environments of Mercury and Mars. At Mercury and Mars, magnetic fields arise from “internal sources” such as fluid motions in the metallic core and/or magnetization of crustal rocks, and from “external sources” such as current systems generated high above the planet’s surface. The resulting environments provide fundamental clues about each planet’s interior, its evolution and its interaction with the solar wind (the stream of charged particles that flows outward from the sun). Past and present interactions with the solar wind have important consequences. For example, the remarkable history of surface water on Mars is tied partly to the resilience of the planet’s atmosphere against erosion by the solar wind. In contrast, on Mercury, direct bombardment of the surface is possible but not yet fully quantified. This process can modify the surface (space weathering), and eject atoms and molecules to form a tenuous atmosphere (exosphere). Finally, time-variations in external magnetic fields (e.g., driven by the solar wind) can generate electrical currents in the planetary interior that produce secondary magnetic fields. Such fields are a unique probe of interior electrical conductivity structure.