Geophysical Investigations of Mars and Mercury

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My research focuses on geophysical investigations of terrestrial planets, moons and small bodies in our solar system. The proposed research program is broadly aimed at exploiting data returned from recent space missions to address key knowledge gaps related to the histories and current states of Mars and Mercury. Common to the investigations are fundamental constraints offered by observed magnetic fields on planetary interior structure and evolution, as well as on atmospheric and magnetospheric processes. 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, processes occurring in the upper atmosphere and the space environment around the planet, and how these internal and external processes interact to shape a planet's evolution. We will investigate the nature and history of Mercury's crustal magnetic field using orbital data from the MESSENGER mission (2011-2015). Investigations of crustal magnetic fields will elucidate the distribution and origin of magnetization in the crust and the history of the core dynamo. A novel aspect of the proposed program is to quantify whether enhanced magnetizations associated with some craters reflect impact-delivered iron enhancements. This can provide an innovative way to constrain the impactor population at Mercury: namely, the relative proportions of iron-bearing versus iron-free impactors. We will also develop thermal evolution models for Mercury, that are critically motivated by the challenge of satisfying three constraints on Mercury's early evolution: extensive early effusive volcanism, substantial planetary contraction and a dynamo. Studies of Mars aim to understand the nature and origin of time variations in the Martian surface magnetic field, measured for the first time by the InSight lander on Mars (Dec. 2018 - present). We will use these data, together with satellite observations from the MAVEN mission (Nov. 2014 - present), to probe the planet's interior electrical conductivity structure, that in turn is related to interior temperature, composition and volatile content. A further aspect involves using crustal field models, surface geology and the record of impact craters to elucidate the history of the Martian dynamo as well as the depths of crustal magnetization. The proposed research program is a key, practical approach to investigating important physical processes that govern the evolution of planets in our own and other solar systems. Funded personnel will contribute to international planetary missions and receive high-level training in planetary physics, computing and data analysis, preparing them for a broad range of opportunities in academia, government or private industry.