Compositional Enhancement of Crustal Magnetization on Mars

Martian orbital and lander measurements revealed strong (∼1–2 orders of magnitude greater than Earth) crustal magnetic anomalies and the lack of an active detectable core dynamo. This strong crustal magnetization remains unexplained given that models of an ancient core dynamo on Mars predict surface field strengths comparable to modern Earth. We explored the relationship between Mars' crustal magnetization and its composition in multivariate space. We identified that 530 and 1,000 nm absorptions (from orbital spectrometers) have unique correlations with crustal magnetization in the Terra Sirenum-Terra Cimmeria region and ∼13% of the variance of the magnetization can be attributed to these correlations. Because we do not expect the topmost material, detectable by the orbital spectrometers, to retain magnetization from an ancient core dynamo, we propose this material is compositionally similar to the bulk rock below it, which is more likely to retain magnetization. Therefore, the observed variance is a lower limit.