Paleomagnetic studies of Apollo samples indicate that the Moon generated a core dynamo lasting for at least 2 billion years. However, the geometry of the lunar magnetic field is still largely unknown because the original orientation of nearly all Apollo samples are unconstrained. Determining the direction of the lunar magnetic field over time could elucidate the mechanism by which the lunar dynamo was powered, whether the magnetic field underwent reversals, and whether the Moon experienced true polar wander. I will present measurements of the lunar magnetic field at 3.7 Ga as recorded by Apollo 17 mare basalts 75035 and 75055. These samples formed as part of basalt flows that make up wall-rock within Camelot crater in the Taurus-Littrow valley. Using layering in the parent boulder for 75055, we inferred its original paleohorizontal orientation on the lunar surface at the time of magnetization. We find that 75035 and 75055 record mean paleointensities of 37.3 ± 5.4 µT and 43.6 ± 4.6 µT, respectively. Furthermore, 75055 records a paleoinclination of 34 ± 11°. This inclination is consistent with, but does not require, a selenocentric axial dipole. Additionally, although true polar wander is also not required by our data, polar wander inferred from independent studies is consistent with our reported paleoinclination.
Speaker: Speaker: Claire Nichols, University of Oxford
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