Compositional Enhancement of Crustal Magnetization on Mars

Abstract

Satellite and ground-based measurements have demonstrated that Mars' ancient crust was magnetized during its formation and/or cooling and that currently there is no detectable core dynamo (Acuña et al., 1999; Connerney et al., 2004; Johnson et al., 2020). The geographic extent and uniformity of the magnetic field indicates that a steady ambient field persisted for at least a few hundred million years, implying an ancient internally generated magnetic field (Acuña et al., 1999). The Terra Sirenum-Terra Cimmeria (TSTC) region hosts particularly strong remanent magnetization, generating crustal fields predicted to be up to a few thousand nanotesla, more than an order of magnitude stronger than magnetic anomalies observed on other terrestrial planets or the Moon (Figure 1; Langlais et al., 2019). Possible explanations for the strongly magnetized crust in TSTC include one or more of the following: (1) a strong ancient magnetic field; (2) magnetized crust of a large depth/volume (3) magnetic minerals particularly well-suited for recording magnetization, for example, with a strong saturation magnetization; and/ or (4) a magnetized unit with a lithology rich in magnetic minerals (Dunlop & Arkani-Hamed, 2005; Stevenson, 2001).

Early crustal processes revealed by the ejection site of the oldest martian meteorite

“…Since this terrain is overprinted by the Hellas and Argyre basins' ejecta materials, formed earlier than ~4.1 Ga, this region is likely a relic of the most ancient crust 40 , which is confirmed by the location of the NWA 7034 ejection site. The compositional effect of the crust on the magnetic intensity 41 suggests that TCTS remained largely unaffected by demagnetizing processes since the pre-Noachian, and that surface material has not been mixed with the surrounding Noachian regolith. This is consistent with a thick crustal block 40 , whose distinct formation and evolution possibly reflect the first stage of differentiation occurring very early in the history of the planet.…”

Exploring Martian Magnetic Fields with a Helicopter

“…However, the source depth uncertainties in such models are large (Gong & Wieczorek 2021). Locally, magnetization has been shown to be at least partially surficial in the Medusa Fossae formation, particularly Lucus Planum (Mittelholz et al 2020a;Ojha & Mittelholz 2023), and in comparison with orbital spectrometer data, composition has been shown to correlate with higher magnetic fields (AlHantoobi et al 2021).…”

High Remanent Magnetization Measured in Hydrothermally Altered Lavas

“…An oxidizing environment could also enhance titanomagnetite (Johnson & Merrill, 1973). Compositional iron enrichment is also thought to be a cause for strong crustal magnetization on the Terra Cimmeria‐Sirenum region of Mars (AlHantoobi et al., 2020; Ojha et al., 2021). Alteration‐related enhancement in magnetization is also thought to have played a role at the Haughton impact structure where post‐impact hydrothermal alteration led to the crystallization of magnetite (Zylberman et al., 2017).…”