X‐Ray Amorphous Sulfur‐Bearing Phases in Sedimentary Rocks of Gale Crater, Mars

The Curiosity rover in Gale crater is investigating a mineral transition observed from orbit – an older “clay unit” to younger “sulfate hypothesized reflect the aridification of Mars’ climate. Below this transition, detected crystalline Ca-sulfates with minor Fe-sulfates but also found that some fraction rock’s bulk SO3 often poorly constrained X-ray amorphous component. Here, we characterize abundances and compositions sulfur-bearing phases 19 drilled samples using mass balance approach, subset 5 evolved SO2 gas measured by SAM instrument. We find ∼20-90 wt% sample’s state phase are consistent mixtures Mg-S, Fe-S, possibly Ca-S phases, likely sulfates or sulfites. These reside bedrock, perhaps as cementing agents deposited detrital sediments during early diagenesis, diagenetic alteration halos after lithification late diagenesis. presence highly soluble Mg-sulfates rocks suggests negligible fluid flow through bedrock post-Mg-sulfate deposition. probably became dehydration current Martian atmosphere inside CheMin materials contribute orbital spectral detections sulfates, so our results help form multiple hypotheses be tested sulfate unit important for understanding evolution surface environment at crater.