Assessing the Crustal Source Depth and Cause of Magnetization North of Caloris Planitia, Mercury

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Date
2023
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University of Alabama Libraries
Abstract

The Mercury Surface, Space ENvironment, Geochemistry, and Ranging (MESSENGER) spacecraft made history as the first to orbit Mercury, the innermost planet of our solar system. During its low-altitude orbits, MESSENGER recorded magnetic signals originating from the crust of Mercury. Initial analysis of these measurements revealed short-scale features that were consistent across orbits. However, the underlying geological processes responsible for these observed crustal magnetic field features remain uncertain. One hypothesis is that the magnetic features were formed in the ejecta blankets of impactors. According to this hypothesis, the impactor material would mix with the crustal material, settle as the ejecta blanket, cool, and then become magnetized in an active core magnetic field. As Mercury's crust typically contains a low amount of magnetic carriers, the introduction of impactor material could locally enhance the presence of magnetic minerals. In this study, I aim to test this hypothesis by investigating the depth of the magnetic sources within a specific region in Mercury's northern hemisphere. The chosen region spans latitudes 48° N to 70° N, and longitudes 115° E to 225° E. This region is north of Caloris Planitia, the largest impact crater on Mercury. My findings reveal that the depth to magnetization in the study region is between 50 km to 60 km and thus significantly exceeds the estimated maximum thickness of the ejecta blanket, which is less than one km. This outcome suggests that the original hypothesis may be incomplete. Whereas the magnetic field observed in the study region may still be associated with the Caloris impact, it is likely influenced by the impact's effects at greater depths rather than solely being caused by the ejecta blanket near the surface.

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Electronic Thesis or Dissertation
Keywords
Caloris Planitia, crustal magnetic fields, magnetization, Mercury, source depth
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