Bounding the Unknowns of Martian Crustal Heat Flow From a Synthesis of Regional Geochemistry and Insight Mission Data

Abstract

The thermal evolution of terrestrial planets is primarily modulated by the distribution of heat-producing elements (HPE) within the crust and mantle. Chemical data from Martian meteorites suggest that Mars differentiated early, which led to an early partitioning of incompatible heat-producing elements in the crust from the mantle. Previous estimates of Martian crustal heat flow that used the bulk regolith abundances of HPEs from the Gamma‐Ray Spectrometer (GRS) suite on Mars Odyssey spacecraft have further corroborated this view of Mars, albeit with poorly known crustal column representativeness. Here we couple the GRS-derived chemical maps of Mars with estimates of crustal thickness and density from the InSight lander to revise the estimated Martian crustal heat flow. The mean crustal heat flow values range from 2.6 to 6.6 mW m^-2 for Insight’s end-member crustal thickness models. We also estimate uncertainty in the crustal heat flow from other factors such as the distribution of HPE with depth and the Uranium content of the crust. Our results suggest that the mean crustal heat flow varies substantially across models, with the highest mean values being associated with higher densities and constant crustal enrichment with depth. Further work is needed to constrain the crustal thickness of Mars, as the largest uncertainties in heat flow calculations reside in the crustal thickness models, not geochemical variability. The results from this work corroborate previous estimates of a strong fractionation of heat-producing elements into the Martian crust.