¹Rhianna D.Moore,¹Anna Szynkiewicz
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2022.115342]
¹Dept. of Earth and Planetary Sciences, University of Tennessee, Knoxville, TN, United States of America
Copyright Elsevier

The Meridiani Planum region on Mars has extensive sulfate-rich sedimentary deposits (~20 wt% SO42−) that are hypothesized to have formed from regional groundwater upwelling that led to the precipitation of secondary Fe-, Mg-, Ca-sulfate minerals and cementation of basaltic sediments. However, the primary source of sulfur (S) for these abundant secondary sulfate minerals is unclear. Therefore, in this study the contributions of volcanic S via surface water and groundwater were investigated in the terrestrial basaltic analogs of Hawaii and Iceland to determine the importance of active volcanism and climate on S cycling as well as the resulting timescale of aqueous activity in the Meridiani Planum region. SO42− fluxes (contributions) were calculated in metric tons/yr using historical data from online repositories and normalized to the catchment area to determine the SO42− load in metric tons/yr/km2. Our results show that the SO42− load is greatly affected by climate, typically ranging from ~7.3 to 170 metric tons/yr/km2 under wetter conditions and ~ 2.6 to 43 metric tons/yr/km2 under dry conditions. Active S degassing and accompanying S-rich mineralization from current hydrothermal activity greatly increased the SO42− loads (~2.8 to 170 metric tons/yr/km2) compared to non-active catchments (2.6 to 13 metric tons/yr/km2). Younger basaltic bedrock with greater permeability and groundwater-rock interactions was also found to be important, resulting in higher SO42− loads (~26 to 170 metric tons/yr/km2) compared to older, less permeable catchments (~2.6 to 12 metric tons/yr/km2). Based on these terrestrial SO42− loads in Hawaii and Iceland, we calculated a range of possible loads and timescales of SO42− transport in Meridiani Planum under variable environmental conditions. Results show that the smallest SO42− loads and longest timescales would occur in Meridiani under dry, non-volcanically active conditions, typically requiring ~16 to 65 Ma of an active aqueous system, as in the older catchments of Hawaii and Iceland. Conversely, the largest SO42− fluxes and shortest timescales would occur under wet, volcanically active conditions, requiring ~1.0 to 6.9 Ma, as in the younger catchments of Hawaii and Iceland. Our results suggest that moderately wet conditions with some active hydrothermal S input would be needed to transport and deposit the equivalent mass of SO42− currently present in the sulfate-rich deposits of Meridiani Planum.