Midlatitudinal hydrated sulfates on Mars may influence brine pH, atmospheric humidity, and collectively water activity. These factors affect the habitability of the planetary subsurface and the preservation of relict biomolecules. Regolith at grain sizes smaller than gravel, constituting the bulk of the Martian subsurface at regional scales, may be a primary repository of chemical alteration, mechanical alteration, and biosignatures. The Mars Odyssey Gamma Ray Spectrometer with hundreds of kilometers of lateral resolution and compositional sensitivity to decimeter depth provides unique insight into this component of the regolith, which we call soil. Advancing the globally compelling association between H2O and S established by our previous work, we characterize latitudinal variations in the association between H and S, as well as in the hydration state of soil. Represented by H2O:S molar ratios, the hydration state of candidate sulfates increases with latitude in the northern hemisphere. In contrast, hydration states generally decrease with latitude in the south. Furthermore, we observe that H2O concentration may affect the degree of sulfate hydration more than S concentration. Limited H2O availability in soil-atmosphere exchange and in subsurface recharge could explain such control exerted by H2O on salt hydration. Differences in soil thickness, ground ice table depths, atmospheric circulation, and insolation may contribute to hemispheric differences in the progression of hydration with latitude. Our observations support chemical association of H2O with S in the southern hemisphere as suggested by Karunatillake et al. (2014), including the possibility of Fe sulfates as a key mineral group.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/621428 |
| Date | 07 1900 |
| Creators | Karunatillake, Suniti, Wray, James J., Gasnault, Olivier, McLennan, Scott M., Deanne Rogers, A., Squyres, Steven W., Boynton, William V., Skok, J. R., Button, Nicole E., Ojha, Lujendra |
| Contributors | Univ Arizona, Dept Planetary Sci, Geology and Geophysics; Louisiana State University; Baton Rouge Louisiana USA, Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA, Université de Toulouse [UPS; OMP; IRAP]; Toulouse France, Department of Geosciences; Stony Brook University; Stony Brook New York USA, Department of Geosciences; Stony Brook University; Stony Brook New York USA, Department of Astronomy; Cornell University; Ithaca New York USA, Department of Planetary Sciences; University of Arizona; Tucson Arizona USA, Geology and Geophysics; Louisiana State University; Baton Rouge Louisiana USA, Geology and Geophysics; Louisiana State University; Baton Rouge Louisiana USA, Earth and Atmospheric Sciences; Georgia Institute of Technology; Atlanta Georgia USA |
| Publisher | AMER GEOPHYSICAL UNION |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | Article |
| Rights | ©2016. American Geophysical Union. All Rights Reserved. |
| Relation | http://doi.wiley.com/10.1002/2016JE005016 |
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