EEPS Colloquium: Catherine Johnson

Catherine Johnson, Planetary Scientist and Professor of Geophysics

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.  Mercury’s global core field might be expected to be stronger and more complex than Earth’s given the planet’s large core, yet the opposite is true.  Why?   This strange core field has a unique and dynamic interaction with the solar wind allowing us to probe interior electrical conductivity structure.  At Mars and Moon, the crustal magnetic field provides information on prior dynamo timing, but at Mercury the story appears to be more complicated, with tantalizing hints that crustal magnetic fields may be diagnostic of variations in crustal iron content not seen in spectral observations of the surface.   Here, 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.

Host: Scott VanBommel

EEPS colloquia are made possible by the William C. Ferguson Fund

_{Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington}