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Published June 2016 | metadata_only
Journal Article

High concentrations of manganese and sulfur in deposits on Murray Ridge, Endeavour Crater, Mars


Mars Reconnaissance Orbiter HiRISE images and Opportunity rover observations of the ~22 km wide Noachian age Endeavour Crater on Mars show that the rim and surrounding terrains were densely fractured during the impact crater-forming event. Fractures have also propagated upward into the overlying Burns formation sandstones. Opportunity's observations show that the western crater rim segment, called Murray Ridge, is composed of impact breccias with basaltic compositions, as well as occasional fracture-filling calcium sulfate veins. Cook Haven, a gentle depression on Murray Ridge, and the site where Opportunity spent its sixth winter, exposes highly fractured, recessive outcrops that have relatively high concentrations of S and Cl, consistent with modest aqueous alteration. Opportunity's rover wheels serendipitously excavated and overturned several small rocks from a Cook Haven fracture zone. Extensive measurement campaigns were conducted on two of them: Pinnacle Island and Stuart Island. These rocks have the highest concentrations of Mn and S measured to date by Opportunity and occur as a relatively bright sulfate-rich coating on basaltic rock, capped by a thin deposit of one or more dark Mn oxide phases intermixed with sulfate minerals. We infer from these unique Pinnacle Island and Stuart Island rock measurements that subsurface precipitation of sulfate-dominated coatings was followed by an interval of partial dissolution and reaction with one or more strong oxidants (e.g., O_2) to produce the Mn oxide mineral(s) intermixed with sulfate-rich salt coatings. In contrast to arid regions on Earth, where Mn oxides are widely incorporated into coatings on surface rocks, our results demonstrate that on Mars the most likely place to deposit and preserve Mn oxides was in fracture zones where migrating fluids intersected surface oxidants, forming precipitates shielded from subsequent physical erosion.

Additional Information

© 2016 Mineralogical Society of America. Open Access, thanks to the authors' funding. Article available to all readers via GSW (http://ammin.geoscienceworld.org) and the MSA web site. Manuscript received October 20, 2015; Manuscript accepted February 5, 2016; First Published on June 02, 2016. Manuscript handled by Richard April. We thank the Opportunity Project Team at the NASA/Caltech Jet Propulsion Laboratory and scientists from many institutions who made possible the collection of data included in this paper. We thank Paolo Bellutta for help in localizing APXS fields of view and Susan Slavney and Jennifer Ward for careful review and editing of text and figures. Bonnie Redding, U.S. Geological Survey, kindly generated the MI anaglyphs. We also thank NASA for the support needed to operate Opportunity and collect and analyze the data included in this paper and the Mars Fundamental Research Program support to J.G. Catalano. The NASA Planetary Data System Geosciences Node houses the data included in this paper and we thank them for their efforts. See http://pds-geosciences.wustl.edu/. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

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August 20, 2023
August 20, 2023