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Article Dans Une Revue Journal of Geophysical Research. Planets Année : 2024

Constraints on the Spatial Distribution of Lunar Crustal Magnetic Sources From Orbital Magnetic Field Data

Résumé

Spacecraft measurements show that the crust of the Moon is heterogeneously magnetized. The sources of these magnetic anomalies are yet not fully understood, with most not being related to known geological structures or processes. Here, we use an inversion methodology that relies on the assumption of unidirectional magnetization, commonly referred to as Parker's method, to elucidate the origin of the magnetic sources by constraining the location and geometry of the underlying magnetization. This method has been used previously to infer the direction of the underlying magnetization but it has not been tested as to whether it can infer the geometry of the source. The performance of the method is here assessed by conducting a variety of tests, using synthetic magnetized bodies of different geometries mimicking the main geological structures potentially magnetized within the lunar crust. Results from our tests show that this method successfully localizes and delineates the two-dimensional surface projection of subsurface three-dimensional magnetized bodies, provided their magnetization is close to unidirectional and the magnetic field data are of sufficient spatial resolution and reasonable signal-to-noise ratio. We applied this inversion method to two different lunar magnetic anomalies, the Mendel-Rydberg impact basin and the Reiner Gamma swirl. For Mendel-Rydberg, our analysis shows that the strongest magnetic sources are located within the basin's inner ring, whereas for Reiner Gamma, the strongest magnetic sources form a narrow dike-like body that emanates from the center of the Marius Hills volcanic complex. Plain Language Summary Magnetometers onboard spacecraft have detected magnetic field signals originating from the lunar crust. These signals are known as magnetic anomalies and are generated by rocks that are permanently magnetized. Lunar magnetic anomalies are distributed heterogeneously over the lunar surface and the geological processes that gave rise to them is under debate. By inferring the shape of the underlying magnetized material, we can constrain these processes and shed light on the Moon's geological history. In this study, we evaluate the ability of a methodology up to now used to infer the direction of the magnetization, to recover the location and shape of the magnetized material. Through a series of tests, we show that this method can constrain the shape of the source of a magnetic anomaly, provided that the respective part of the crust is magnetized along a common direction. We then apply the method to two lunar magnetic anomalies. The inferred shape and location are in good agreement with the associated geological features and suggest that one originated by an impact event and the other by volcanic activity. Future applications can focus on constraining the origin of the many lunar magnetic anomalies that are not associated with visible geological features.
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Dates et versions

hal-04471841 , version 1 (21-02-2024)

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Joana S Oliveira, Foteini Vervelidou, Mark A Wieczorek, Marina Díaz Michelena. Constraints on the Spatial Distribution of Lunar Crustal Magnetic Sources From Orbital Magnetic Field Data. Journal of Geophysical Research. Planets, 2024, 129 (2), ⟨10.1029/2023je008125⟩. ⟨hal-04471841⟩
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