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Constraining the Hydration of Clay Minerals and Abundances of Amorphous Phases in Gale Crater, Mars.

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Title: Constraining the Hydration of Clay Minerals and Abundances of Amorphous Phases in Gale Crater, Mars.
Authors: Czarnecki, Sean1,2 (AUTHOR) sczarnecki@lanl.gov, Hardgrove, Craig1 (AUTHOR), Rampe, Liz3 (AUTHOR), Gasda, Patrick2 (AUTHOR)
Source: Journal of Geophysical Research. Planets. May2026, Vol. 131 Issue 5, p1-24. 24p.
Subject Terms: *Clay minerals, *Sorption, Gale Crater (Mars), Amorphous substances, Mars (Planet), Smectite, Hydration, Water-rock interaction
Company/Entity: Curiosity (Spacecraft)
Abstract: 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 Curiosity rover has investigated several hundred meters of stratigraphy in Gale crater, including where clays were detected from orbit. Previous results have suggested that subsurface hydration is greatest in units with the most abundant clays, suggesting that these minerals may be hydrated. Organics have also been found throughout Gale crater. Smectites are the most common and abundant phyllosilicates in Gale crater samples and can expand and sorb water and organics in interlayer sites. The most common organic sorption processes on Earth typically involve water or hydroxyl, so hydrated phyllosilicates are good candidates for organic preservation. Using newly derived subsurface hydration results with previously published mineralogy and geochemistry, we derived modeled 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 phases constrained here. We found correlations between smectites and both "excess" water and "excess" cation abundances, indicating that smectites in Gale crater are hydrated and that cation bridging could be a mechanism for sorption of organics. Our results also show the persistence of amorphous sulfates, opal‐A, and volcanic or impact glass, which indicate low water‐rock interactions. Increased abundances of sulfates and glass in stratigraphically higher samples may indicate lower water availability and environmental aridification during the time these units were being deposited. Plain Language Summary: Water and organic matter are required for the development of life. Clay minerals have high surface areas that easily bind both water and organic matter. The Curiosity rover has investigated regions of Gale crater where clays were previously detected. Previous results suggest that hydration is greatest in the most clay‐rich regions, and that these clays may be hydrated. The most common organic binding processes on Earth typically involve water, so hydrated clays are good candidates for organic preservation. Using new hydration results with previous results, we constrained the abundances of amorphous materials, "excess" water, and other "excess" elements. "Excess" water is not accounted for by published mineral abundances or by poorly structured minerals constrained here. We found correlations between clays and both "excess" water and other "excess" elements, indicating that clays in Gale crater are hydrated and that this water could bind organics through these other "excess" elements. Our results also show significant amounts of certain poorly structured minerals which tend to be altered by water, indicating low water activity over time. Increased amounts of some poorly structured minerals higher up Gale crater's central mound may indicate lower water availability and environmental drying during the time Gale crater was being filled with sediment. Key Points: A correlation between "excess" hydration and smectite abundances indicates that smectites in Gale crater are hydratedCorrelations between "excess" cations and smectite abundances suggest that cation bridging may bind water and organics to smectitesAmorphous phase abundances indicate low water‐rock interactions in the syn‐ and post‐depositional history of Gale crater [ABSTRACT FROM AUTHOR]
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Abstract: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 Curiosity rover has investigated several hundred meters of stratigraphy in Gale crater, including where clays were detected from orbit. Previous results have suggested that subsurface hydration is greatest in units with the most abundant clays, suggesting that these minerals may be hydrated. Organics have also been found throughout Gale crater. Smectites are the most common and abundant phyllosilicates in Gale crater samples and can expand and sorb water and organics in interlayer sites. The most common organic sorption processes on Earth typically involve water or hydroxyl, so hydrated phyllosilicates are good candidates for organic preservation. Using newly derived subsurface hydration results with previously published mineralogy and geochemistry, we derived modeled 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 phases constrained here. We found correlations between smectites and both "excess" water and "excess" cation abundances, indicating that smectites in Gale crater are hydrated and that cation bridging could be a mechanism for sorption of organics. Our results also show the persistence of amorphous sulfates, opal‐A, and volcanic or impact glass, which indicate low water‐rock interactions. Increased abundances of sulfates and glass in stratigraphically higher samples may indicate lower water availability and environmental aridification during the time these units were being deposited. Plain Language Summary: Water and organic matter are required for the development of life. Clay minerals have high surface areas that easily bind both water and organic matter. The Curiosity rover has investigated regions of Gale crater where clays were previously detected. Previous results suggest that hydration is greatest in the most clay‐rich regions, and that these clays may be hydrated. The most common organic binding processes on Earth typically involve water, so hydrated clays are good candidates for organic preservation. Using new hydration results with previous results, we constrained the abundances of amorphous materials, "excess" water, and other "excess" elements. "Excess" water is not accounted for by published mineral abundances or by poorly structured minerals constrained here. We found correlations between clays and both "excess" water and other "excess" elements, indicating that clays in Gale crater are hydrated and that this water could bind organics through these other "excess" elements. Our results also show significant amounts of certain poorly structured minerals which tend to be altered by water, indicating low water activity over time. Increased amounts of some poorly structured minerals higher up Gale crater's central mound may indicate lower water availability and environmental drying during the time Gale crater was being filled with sediment. Key Points: A correlation between "excess" hydration and smectite abundances indicates that smectites in Gale crater are hydratedCorrelations between "excess" cations and smectite abundances suggest that cation bridging may bind water and organics to smectitesAmorphous phase abundances indicate low water‐rock interactions in the syn‐ and post‐depositional history of Gale crater [ABSTRACT FROM AUTHOR]
ISSN:21699097
DOI:10.1029/2025JE009199