by Prof. Catherine Johnson
from Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia
Wednesday, Feb. 23, 2022 from 4:10pm - 5:30pm (EST)
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Planetary magnetic fields provide indirect, but fundamental, constraints on the internal structure and evolution of terrestrial planetary bodies. The presence of a global magnetic field, generated in a metallic core today or in the past, is intimately tied to core composition, structure, and the cooling history of a planet. Crustal magnetization yields a record of the net effects of the dynamo history, silicate iron mineralogy and processes that have modified the crust over time. The interaction of a planet, its atmosphere and any crustal or core magnetic field with the solar wind results in time-varying fields that can be global or local in spatial scale, and periodic or transient in nature. These can induce electrical currents in the planets interior that result in secondary magnetic fields. Such secondary induced fields are sensitive probes of interior electrical conductivity structure that in turn depends on temperature and composition, in particular volatile content. Over the past decade new data sets, sensitive laboratory techniques and advances in modeling have clearly shown that Mercury, Venus, Earth, Mars, and the Moon each possess unique magnetic field characteristics, providing key insights into the diversity of planetary histories in our own Solar System and beyond. Here I will review some recent discoveries, highlighting outstanding puzzles.
Catherine Johnson is a Professor of Geophysics at the University of British Columbia, Vancouver and a Senior Scientist at the Planetary Science Institute, Tucson. Her research focuses on understanding the structure and interior evolution of terrestrial planets, moons and asteroids. She was a Participating Scientist on the MESSENGER (Mercury) mission and is currently a Co-Investigator on the InSight (Mars) and OSIRIS-REx (asteroid Bennu) missions. She is a fellow of the AGU and in 2019 was the recipient of the Price Medal of the Royal Astronomical Society and the IAGA Shen Kuo Award. When not nerding out on planets other than Earth she loves gardening, cooking, hiking and teaching yoga.