Crustal Magnetization Source Depths North of the Caloris Basin, Mercury

Abstract Magnetic measurements collected by the MESSENGER spacecraft showed that Mercury has a crustal magnetic field in addition to a core magnetic field. Within the region of data availability, this crustal magnetic field is strongest in the vicinity of the Caloris impact basin. Two origin hypotheses have been proposed for this observation: magmatic intrusions/buried tectonic features, or Caloris ejecta material. We present a local spherical harmonic spectral analysis of the magnetic data north of the Caloris Basin. Our results yield a best‐fitting source depth between 10 and 72 km below the surface. Source depths shallower than 2.5 km differ by more than one standard deviation from an optimal spectral misfit. Models for Mercury's thermal state at 4 Ga limit the source depth to 40 km for iron as magnetic carrier. Magmatic intrusions at depths between 10 and 40 km may be an explanation for the magnetic sources.