The Case of the Disappearing Dynamo: Constraining the decline of the Moon’s magnetic field through experimental analyses of Apollo samples

Dr. Beck Strauss

Monday, May 10, 2021 - 11:00
General Seminar
Dr. Beck Strauss, NIST

Recent paleomagnetic studies of lunar rocks have suggested that the Moon’s magnetic field reached peak intensities on the order of ≈77 µT between 3.85 and 3.56 Ga and subsequently declined to surface intensities of ≈4 µT by 3.19 Ga. However, this decline in the intensity of the lunar field has only been shown in a small number of samples, presenting challenges for constraint of its timing and thus the dynamo generation mechanisms that could be responsible.

We present microscopic and magnetic analyses of Apollo samples 12008, 12009, and 12015, three fine-grained mare vitrophyre basalts with high magnetic fidelity, indicating that these samples were not magnetized in conditions consistent with a planetary magnetic field exceeding ≈4-7 µT during their formation. We then use these three samples as a case study to explore fundamental questions about the relationship between magnetic mineralogy and recording fidelity in lunar rocks.