Observations of high manganese layers by the Curiosity rover at the Kimberley, Gale crater, Mars

Wednesday, 17 December 2014: 5:15 PM
Nina Lanza1, Roger C Wiens1, Woodward W Fischer2, John P Grotzinger2, Agnes Cousin1, Melissa S Rice3, Benton C Clark4, Raymond E Arvidson5, Joel Hurowitz6, Ralf Gellert7, Scott M McLennan6, Sylvestre Maurice8, Nicolas Mangold9, Stephane Le Mouelic10, Ryan B Anderson11, Marion Nachon12, Ann Ollila13, Mariek E Schmidt14, Jeffrey A Berger15, Jennifer G Blank16, Samuel M Clegg1, Olivier Forni8, Craig J Hardgrove17, Keian Hardy18, Jeffrey Roy Johnson19, Noureddine Melikechi20, Horton E Newsom21, Violaine Sautter10, Javier Martín-Torres22 and Maria-Paz Zorzano22, (1)Los Alamos National Laboratory, Los Alamos, NM, United States, (2)Caltech, Pasadena, CA, United States, (3)California Institute of Technology, Pasadena, CA, United States, (4)Space Science Institute Boulder, Boulder, CO, United States, (5)Washington University in St Louis, St. Louis, MO, United States, (6)Stony Brook University, Stony Brook, NY, United States, (7)University of Guelph, Guelph, ON, Canada, (8)IRAP, Toulouse, France, (9)LPGN Laboratoire de Planétologie et Géodynamique de Nantes, Nantes Cedex 03, France, (10)CNRS, Paris Cedex 16, France, (11)USGS Astrogeology Science Center, Flagstaff, AZ, United States, (12)University of Nantes, Nantes, France, (13)Chevron Corporation Houston, Houston, TX, United States, (14)Brock University, St Catharines, ON, Canada, (15)University of Western Ontario, Earth Science, London, ON, Canada, (16)NASA Ames Research Center, Moffett Field, CA, United States, (17)Arizona State University, Tempe, AZ, United States, (18)US Naval Academy, Annapolis, MD, United States, (19)Applied Physics Laboratory, Laurel, MD, United States, (20)Delaware State University, Dover, DE, United States, (21)Univ New Mexico, Albuquerque, NM, United States, (22)Centro de Astrobiologia, Madrid, Spain
The Curiosity rover spent sols 606-630 analyzing an outcrop in a region dubbed the Kimberley. Three rock targets at this location were found to have Mn concentrations strongly elevated above that of martian primary crust: Stephen (sols 611, 619, 630), Neil (sol 619), and Mondooma (sol 625). Stephen and Neil are adjacent to one another and appear as more resistant, fin-like layers subparallel to sedimentary bedding, and are interpreted as bedding-parallel mineralized fractures. Mondooma is located in the same bedrock unit a few meters away and has a similar geological context. After dust cleaning by ChemCam, Stephen and Neil exhibited dark, shiny surfaces. The dust-cleared surface of Mondooma is also dark and exhibits an angular, shallow fracture pattern. ChemCam observations indicate high Mn concentrations (~20-40 wt% MnO) for all three targets in which Mn abundances are higher in the first shots and decrease systematically with succeeding shots (i.e. increasing depths). The Alpha Particle X-ray Spectrometer (APXS) also analyzed Stephen (sols 627, 629) and observed elevated manganese abundances (~4 wt% MnO) that are the highest detected by that instrument in Gale thus far. APXS data show that Stephen also exhibits relatively high Ni abundances (~1000 ppm) that correlate with Mn. The difference between the two instruments’ measurements is likely due to differences in interaction volumes and footprint areas (1.7 cm APXS versus ~400 μm ChemCam). In addition to these three high Mn targets, other fin-like features are observed throughout the unit. Based on morphology and chemistry, these thin Mn-rich fins likely represent fracture-filling authigenic minerals emplaced by secondary fluids percolating through the strata. The appearance and correlation between Mn and Ni strongly suggest the presence of Mn-oxide phase(s). Mn-oxides are important because they require extremely strong oxidants and sufficient volumes of liquid water to form. Environments of Mn cycling on Earth are uniformly habitable and Mn-oxides provide for the microbial respiration of a wide variety of reduced compounds. Thus, these results suggest that Mars may have hosted a broader range of habitable environments than previously recognized.