Speaker/Affiliation: Ji-In Jung, Stanford University
Title: Evolution of the Lunar Dynamo
When: Friday, February 13 12:00pm PST
Location: EMS B214
Abstract: Lunar crustal magnetism revealed by orbital measurements and paleomagnetic analyses of Apollo samples overturned the long-held view of the Moon as magnetically inert. Paleointensity estimates suggest surface fields as strong as ~40–110 μT between ~3.9 and 3.5 Ga, declining to ~10–20 μT by ~3.2 Ga and ceasing by ~0.9 Ga. Yet the origin of such an intense and long-lived field remains unresolved: the Moon’s small core is unlikely to sustain a conventional convective dynamo or unconventional dynamo mechanisms. Adding to this uncertainty, some studies suggest that strong remanent magnetizations in Apollo samples may reflect secondary overprints from impacts or spacecraft-related fields rather than a core-generated dynamo. Further challenges arise from the poor magnetic recording properties of lunar samples. Whether the Moon truly hosted a global magnetic field—and what mechanisms powered it—therefore remains a central open question in lunar science.
In this talk, we investigate the origin and variability of the lunar magnetic field by integrating recent paleomagnetic, rock-magnetic, and microscopy-based analyses. We focus on weakly magnetized Apollo samples from the high-field epoch (3.9–3.5 Ga), combining SEM, TEM, quantum diamond microscopy (QDM), and low-temperature magnetic measurements to evaluate their reliability as paleomagnetic recorders. We further present a suite of controlled laboratory experiments designed to test plausible secondary overprint mechanisms, including spacecraft-induced fields, pressure-related remagnetization, and lunar diurnal thermal cycling. Together, these results offer new insights into the Moon’s magnetic evolution and the dynamo mechanisms that may have driven it during its history.
