Scales of Martian Crustal Magnetization Constrained by MAVEN, InSight, and Zhurong

While Mars does not possess a currently active geodynamo, remanent crustal magnetization has been found across the planet and contains records of the origin, scale, and timing of Martian magnetization. The first in situ measurements of the Martian magnetic field on the planet's surface, at the InSight and Zhurong landing sites, allow for better constraints on magnetization coherence and depth scales near the surface, as crustal fields are closely related to a variety of geological and topographic features. We develop Monte Carlo models of the Martian crustal magnetization near the two landing sites on small-scales (50 km) to meso-scales (100$-$1,000 km) to compute altitude profiles of the magnetic field intensity. We compare our simulations with the Langlais et al. (2019, https://doi.org/10.1029/2018je005854) crustal field model and surface measurements, indicating that power law distributions more accurately describe Martian altitude profiles compared to Gaussian models. Observations are best explained by fractal parameter $\beta$ values near 2.7 and coherence scales roughly 250 km near InSight, with larger coherence scales and possibly thicker crustal magnetization near Zhurong. Motivated by these length scales, we create additional magnetization models based on the geological units near each lander to relate them to different time periods of Martian history. Our results suggest at least one polar field reversal in Martian history based on the simulated magnetization near the North-South dichotomy boundary. Furthermore, we propose that the Martian geodynamo might have weakened or suspended during the late Noachian, followed by revitalization of the core dynamo during the Hesperian period.