^1,2Sean Czarnecki,¹Craig Hardgrove,³Liz Rampe,²Patrick Gasda
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2025JE009199]
¹Arizona State University, Tempe, AZ, USA
²Los Alamos National Laboratory, Los Alamos, NM, USA
³NASA JohnsonSpace Center, Houston, TX, USA
Published by arrangement with John Wiley & Sons

Both water and organic matter are required for the development and persistence of life.Phyllosilicates (clay minerals) have high surface areas that easily sorb water and organic matter. The Curiosityrover has investigated several hundred meters of stratigraphy in Gale crater, including where clays weredetected from orbit. Previous results have suggested that subsurface hydration is greatest in units with the mostabundant clays, suggesting that these minerals may be hydrated. Organics have also been found throughout Galecrater. Smectites are the most common and abundant phyllosilicates in Gale crater samples and can expand andsorb water and organics in interlayer sites. The most common organic sorption processes on Earth typicallyinvolve water or hydroxyl, so hydrated phyllosilicates are good candidates for organic preservation. Usingnewly derived subsurface hydration results with previously published mineralogy and geochemistry, we derivedmodeled constraints on the abundances of hydrated amorphous phases, “excess” water, and “excess” cations.These “excess” phases are not accounted for by published crystalline phase abundances or by amorphous phasesconstrained here. We found correlations between smectites and both “excess” water and “excess” cationabundances, indicating that smectites in Gale crater are hydrated and that cation bridging could be a mechanismfor sorption of organics. Our results also show the persistence of amorphous sulfates, opal‐A, and volcanic orimpact glass, which indicate low water‐rock interactions. Increased abundances of sulfates and glass instratigraphically higher samples may indicate lower water availability and environmental aridification duringthe time these units were being deposited.