Characterizing Martian Primary Crustal Compositions With Gamma Ray Spectroscopy

Abstract Mars's global‐scale chemical maps of the midlatitudes, derived from Mars Odyssey gamma and neutron spectroscopy, have constrained martian geology across a multitude of processes. However, the chemical maps are often used to analyze pre‐defined regions based on mapped geology and/or mineralogy. Previous mapping works have relied on first‐principles methods like principal component analyses and k‐means clustering. In response, we adapt dimensionality reduction and multivariate clustering methods to analyze the spatial variability of nine key elements in martian geochemical maps. We identify seven individually contiguous chemical provinces, nearly exclusively in the highlands. We then conduct geochemical analysis coupled with first order petrological modeling to assess the histories for individually delineated provinces. We identified two new regions where one is consistent with minimal chemical weathering and represents a ∼3.7 Ga old crustal block preserving compositional evidence of fractional crystallization, suggestive of Mars's primary crust sequestering early as a magma ocean solidified.