The lunar magnetic field as recorded by Apollo return samples and implications about the lunar dynamo

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According to spacecraft magnetic field measurements and paleomagnetic studies on Apollo lunar samples, the lunar crust is locally magnetized. The leading hypothesis for the origin of this magnetization is that the Moon, in its past, sustained a lunar core dynamo. This dynamo is now extinct, and little is known about its strength, the duration of its activity and the mechanism that powered it. Shedding light on these questions can improve our understanding about the generation of dynamos on small planetary bodies.

In this talk, I will present results about the intensity of the lunar magnetic field obtained by laboratory measurements on rocks from the Apollo 16 and Apollo 17 missions, with ages ranging from 1.7 to 3.75 Gy old. I will discuss the results in the context of two issues surrounding lunar paleomagnetism. Firstly, the concern about whether the magnetic record of Apollo samples is of lunar origin, as opposed to spacecraft or terrestrial contamination. Secondly, the discrepancy between the Earth-like intensities inferred by paleomagnetic studies during the early phase of the lunar history and the intensities allowed by the available energy budget given Moon’s small metallic core. I will close the talk by discussing the potential of magnetic microscopy to shed further light on the evolution of the lunar dynamo.