Magnetic Field Investigations of Mars and Mercury

点击翻译按钮获取中文摘要

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. ******We will investigate the nature and history of Mercury's internal magnetic field using orbital data from the MESSENGER mission (2011-2015). We will characterize the internal core field to provide critical constraints on state-of-the-art dynamo models. Investigations of crustal magnetic fields will elucidate the distribution and origin of magnetization in the crust and the history of the dynamo. Finally, the proposed work will also identify and understand time-variations in the external field environment and determine how these dynamics couple to Mercury's interior. ******Studies of Mars will use satellite observations returned by the Mars Global Surveyor (1997-2006) and MAVEN (2014 – present) missions, as well as the first-ever surface measurements of Mars' magnetic field from the InSight mission (2016 onwards). Our work will characterize external magnetic fields, probe the electrical conductivity structure of the crust and mantle, and provide improved models for the crustal magnetic field. It will contribute to understanding the structure and origin of the ionosphere (uppermost atmosphere) as well as to constraining the unknown and contentious volatile content of the crust and mantle. ******The proposed magnetic field studies are a key, practical approach to investigating important physical processes that govern the evolution and habitability 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.