EPS Colloquium – Catherine Johnson, University of British Columbia, Vancouver

The Enigmatic Innermost Planet: A Magnetic Field Perspective

Mercury is the only inner solar system planet other than Earth to possess a present-day magnetic field and evidence for crustal magnetization, yet both the core and crustal fields are quite different from their terrestrial counterparts. 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 Mercury’s thermal evolution. 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 Mercury’s global magnetic field with the solar wind also induces secondary magnetic fields that are sensitive probes of interior electrical conductivity structure. In this talk, I will review what we have learned about Mercury’s magnetic field from the MESSENGER mission (2008-2015) and the broader implications for Mercury’s thermal and crustal evolution. I will highlight outstanding puzzles, that can be addressed by future experiments, modeling, and observations. In particular I will touch on questions that can be addressed by the Bepi-Colombo mission that is scheduled to go into orbit around Mercury in November 2026.

To be added to the EPS colloquium mailing list, please contact Caroline Carr at carolinecarr@fas.harvard.edu.

Catherine Johnson is a Professor of Geophysics and Distinguished University Scholar 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, a Co-Investigator on the InSight (Mars) and OSIRIS-REx (asteroid Bennu) missions. She is a member of the U. S. National Academy of Sciences, the American Academy of Arts and Sciences, and a fellow of the Royal Society of Canada and the AGU. When not nerding out on planets other than Earth she loves gardening, cooking, hiking and teaching yoga.