Establishing a Lunar Origin for Paleomagnetic Records in Apollo Samples

Abstract

AbstractNumerous paleomagnetic studies attribute the magnetization preserved within Apollo samples to an ancient dynamo. However, other works propose that lunar rocks were instead magnetized by either transient impact‐related magnetic fields on the Moon or by the return spacecraft. To test whether lunar samples could have been magnetized during return to Earth, sample handling, or transport, we exposed lunar rocks to 5–10 mT fields for varying durations. We then determined how easily these magnetic overprints could be removed and how paleointensity estimates are affected by the overprints and their removal. We found that magnetic overprints were cleaned by alternating field (AF) demagnetization to ∼10–30 mT for nearly all samples and that acceptable paleointensities may be obtained from higher AF levels. Therefore, high coercivity (>30 mT) magnetizations observed within lunar rocks are generally not magnetic contamination and were initially acquired on the Moon.