The Relationship of Martian Crustal Remnant Magnetism and Mineralogy
Abstract
Orbital magnetometers and the InSight lander discovered strong crustal magnetic fields (~10 microtesla) in some regions of Mars despite the lack of a detectable core dynamo. This strong crustal magnetism is unexplained given that previous models of Mars' ancient core dynamo are of approximate strength of Earth's current field and would not produce such strong remanent magnetization if Earth-like lithologies are assumed. However, the crust of Mars is more iron-rich than Earth's crust, which may lead to rocks with significant proportions of magnetic phases such as magnetite, hematite, pyrrhotite, and titanomagnetite.
In this study, we explore the relationship between the strength of Mars crustal magnetization and its composition (e.g., iron content, silica content, etc.). Using the recent Langlais (2019) model for Mars crustal magnetism and maps of surface composition from the Gamma Ray Spectrometer and Thermal Emission Spectrometer we computed the Pearson's correlation coefficient for different regions on Mars. We find that in six regions where Mars' crustal field is particularly strong, there is a strong positive Pearson's correlation coefficient between magnetic field strength and iron content (between 0.83 and 0.89, where XX is indicative of a strong positive correlation). These regions are also reduced in silica and have elevated thermal inertia. Previous mapping of Mars places these regions within the early Noachian crust, possibly from when Mars' core dynamo was active. A potential scenario to explain these observations is thermoremanent magnetization of iron-rich basalt with abundant single-domain magnetic carriers such as magnetite and thus high magnetic susceptibility. The combination of compositional indicators and strong magnetic anomalies indicate that there is a regional enhancement of the magnetic field that may be due to mineralogy. Mars' ancient core dynamo therefore need not produce Earth-strength surface intensities. Instead, the rocks may be much better recorders of the magnetic field than typical lithologies available on Earth.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMGP31A..05A
- Keywords:
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- 1507 Core processes;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1510 Dynamo: theories and simulations;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1517 Magnetic anomalies: modeling and interpretation;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1527 Paleomagnetism applied to geologic processes;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1560 Time variations: secular and longer;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 1595 Planetary magnetism: all frequencies and wavelengths;
- GEOMAGNETISM AND PALEOMAGNETISM;
- 5440 Magnetic fields and magnetism;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS