A Caltech Library Service

Large sulfur isotope fractionations in Martian sediments at Gale crater

Franz, H. B. and Fischer, W. W. and Grotzinger, J. P. and Farley, K. A. (2017) Large sulfur isotope fractionations in Martian sediments at Gale crater. Nature Geoscience, 10 (9). pp. 658-662. ISSN 1752-0894.

[img] PDF - Supplemental Material
See Usage Policy.


Use this Persistent URL to link to this item:


Variability in the sulfur isotopic composition in sediments can reflect atmospheric, geologic and biological processes. Evidence for ancient fluvio-lacustrine environments at Gale crater on Mars and a lack of efficient crustal recycling mechanisms on the planet suggests a surface environment that was once warm enough to allow the presence of liquid water, at least for discrete periods of time, and implies a greenhouse effect that may have been influenced by sulfur-bearing volcanic gases. Here we report in situ analyses of the sulfur isotopic compositions of SO_2 volatilized from ten sediment samples acquired by NASA’s Curiosity rover along a 13 km traverse of Gale crater. We find large variations in sulfur isotopic composition that exceed those measured for Martian meteorites and show both depletion and enrichment in ^(34)S. Measured values of δ^(34)S range from −47 ± 14‰ to 28 ± 7‰, similar to the range typical of terrestrial environments. Although limited geochronological constraints on the stratigraphy traversed by Curiosity are available, we propose that the observed sulfur isotopic signatures at Gale crater can be explained by equilibrium fractionation between sulfate and sulfide in an impact-driven hydrothermal system and atmospheric processing of sulfur-bearing gases during transient warm periods.

Item Type:Article
Related URLs:
URLURL TypeDescription ReadCube access ItemPlanetary Data System
Fischer, W. W.0000-0002-8836-3054
Grotzinger, J. P.0000-0001-9324-1257
Farley, K. A.0000-0002-7846-7546
Additional Information:© 2017 Macmillan Publishers Limited, part of Springer Nature. Received 27 September 2016; Accepted 12 July 2017; Published online 07 August 2017. This work was funded by NASA’s Mars Exploration Program. The authors thank T. B. Griswold for assistance with figure preparation, B. Franz for editorial support, J. Farquhar for manuscript review, J. Farquhar and A. J. Kaufman for facilitating isotopic analyses of calibrants, and the technical team at the NASA GSFC Planetary Environments Laboratory for laboratory support. Author Contributions: H.B.F. developed analytical methods, calculated and interpreted sulfur isotope ratios, performed calibration experiments, and wrote the manuscript and most of the Supplementary Information. A.C.M. wrote the mineralogy section of the Supplementary Information. H.B.F., A.C.M. and C.A.K. performed supporting laboratory EGA studies. C.F. contributed to analysis of calibration data. D.L.E. calculated theoretical equilibrium fractionation factors for relevant sulfur-bearing species. H.B.F., J.W.D. and R.P. performed ground-truth isotopic analyses of calibrants. All authors participated in discussion of results and/or editing of the manuscript. The authors declare no competing financial interests. Data availability: All SAM data are available at the Geosciences Node of NASA's Planetary Data System:
Funding AgencyGrant Number
Issue or Number:9
Record Number:CaltechAUTHORS:20170921-091550876
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:81667
Deposited By: Tony Diaz
Deposited On:21 Sep 2017 18:09
Last Modified:03 Oct 2019 18:45

Repository Staff Only: item control page