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Title: Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater

Abstract

The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. Our study of the Bagnold dunes focuses on the ChemCam chemical results and also presents findings on the grain size distributions based on the ChemCam RMI and MAHLI images. These active dunes are composed of grains that are mostly <250 μm. Their composition is overall similar to that of the aeolian deposits analyzed all along the traverse (“Aeolis Palus soils”). Nevertheless, the dunes contain less volatiles (Cl, H, S) than the Aeolis Palus soils, which appears to be due to a lower content of volatile-rich fine-grained particles (<100 μm), or a lower content of volatile-rich amorphous component, possibly as a result of: 1) a lower level of chemical alteration; 2) the removal of an alteration rind at the surface of the grains during transport; 3) a lower degree of interaction with volcanic gases/aerosols; or 4) physical sorting that removed the smallest and most altered grains. Analyses of the >150 μm grain-size dump piles have shown that coarser grains (150-250 μm) are enriched in the mafic elements Fe and Mn, suggesting a larger content in olivine compared to smaller grains (<150 μm) of the Bagnold dunes. Furthermore, themore » chemistry of soils analyzed in the vicinity of the dunes indicates that they are similar to the dune material. Altogether these observations suggest that the olivine content determined by X-ray diffraction of the <150 μm grain-size sample should be considered as a lower limit for the Bagnold dunes.« less

Authors:
 [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1]; ORCiD logo [4]; ORCiD logo [3]; ORCiD logo [5]; ORCiD logo [6];  [1];  [1]; ORCiD logo [7]; ORCiD logo [8]; ORCiD logo [1];  [1]; ORCiD logo [8]
  1. Univ. of Toulouse (France). Inst. for Research in Astrophysics and Planetology (IRAP)
  2. Towson Univ., MD (United States). Dept. of Physics Astronomy and Geosciences
  3. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  4. Applied Physics Lab., Laurel, MD (United States)
  5. German Aerospace Center (DLR), Berlin (Germany)
  6. Univ. of Loraine, Nancy (France)
  7. National Museum of Natural History, Paris (France)
  8. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Research Org.:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE; National Aeronautics and Space Administration (NASA)
OSTI Identifier:
1396139
Report Number(s):
LA-UR-17-27677
Journal ID: ISSN 2169-9097
Grant/Contract Number:
AC52-06NA25396
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Planets
Additional Journal Information:
Journal Volume: 122; Journal Issue: 10; Journal ID: ISSN 2169-9097
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Planetary Sciences

Citation Formats

Agnes, Cousin, Dehouck, Erwin, Meslin, Pierre-Yves, Forni, Olivier, Williams, Amy J., Stein, Nathan, Gasnault, Olivier, Bridges, Nathan, Ehlmann, Bethany, Schröder, Susanne, Payré, Valérie, Rapin, William, Pinet, Patrick, Sautter, Violaine, Lanza, Nina, Lasue, Jérémie, Maurice, Sylvestre, and Wiens, Roger C.. Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater. United States: N. p., 2017. Web. doi:10.1002/2017JE005261.
Agnes, Cousin, Dehouck, Erwin, Meslin, Pierre-Yves, Forni, Olivier, Williams, Amy J., Stein, Nathan, Gasnault, Olivier, Bridges, Nathan, Ehlmann, Bethany, Schröder, Susanne, Payré, Valérie, Rapin, William, Pinet, Patrick, Sautter, Violaine, Lanza, Nina, Lasue, Jérémie, Maurice, Sylvestre, & Wiens, Roger C.. Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater. United States. doi:10.1002/2017JE005261.
Agnes, Cousin, Dehouck, Erwin, Meslin, Pierre-Yves, Forni, Olivier, Williams, Amy J., Stein, Nathan, Gasnault, Olivier, Bridges, Nathan, Ehlmann, Bethany, Schröder, Susanne, Payré, Valérie, Rapin, William, Pinet, Patrick, Sautter, Violaine, Lanza, Nina, Lasue, Jérémie, Maurice, Sylvestre, and Wiens, Roger C.. 2017. "Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater". United States. doi:10.1002/2017JE005261.
@article{osti_1396139,
title = {Geochemistry of the Bagnold dune field as observed by ChemCam and comparison with other aeolian deposits at Gale Crater},
author = {Agnes, Cousin and Dehouck, Erwin and Meslin, Pierre-Yves and Forni, Olivier and Williams, Amy J. and Stein, Nathan and Gasnault, Olivier and Bridges, Nathan and Ehlmann, Bethany and Schröder, Susanne and Payré, Valérie and Rapin, William and Pinet, Patrick and Sautter, Violaine and Lanza, Nina and Lasue, Jérémie and Maurice, Sylvestre and Wiens, Roger C.},
abstractNote = {The Curiosity rover conducted the first field investigation of an active extraterrestrial dune. Our study of the Bagnold dunes focuses on the ChemCam chemical results and also presents findings on the grain size distributions based on the ChemCam RMI and MAHLI images. These active dunes are composed of grains that are mostly <250 μm. Their composition is overall similar to that of the aeolian deposits analyzed all along the traverse (“Aeolis Palus soils”). Nevertheless, the dunes contain less volatiles (Cl, H, S) than the Aeolis Palus soils, which appears to be due to a lower content of volatile-rich fine-grained particles (<100 μm), or a lower content of volatile-rich amorphous component, possibly as a result of: 1) a lower level of chemical alteration; 2) the removal of an alteration rind at the surface of the grains during transport; 3) a lower degree of interaction with volcanic gases/aerosols; or 4) physical sorting that removed the smallest and most altered grains. Analyses of the >150 μm grain-size dump piles have shown that coarser grains (150-250 μm) are enriched in the mafic elements Fe and Mn, suggesting a larger content in olivine compared to smaller grains (<150 μm) of the Bagnold dunes. Furthermore, the chemistry of soils analyzed in the vicinity of the dunes indicates that they are similar to the dune material. Altogether these observations suggest that the olivine content determined by X-ray diffraction of the <150 μm grain-size sample should be considered as a lower limit for the Bagnold dunes.},
doi = {10.1002/2017JE005261},
journal = {Journal of Geophysical Research. Planets},
number = 10,
volume = 122,
place = {United States},
year = 2017,
month = 6
}

Journal Article:
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  • The Mars Science Laboratory Curiosity rover performed coordinated measurements to examine the textures and compositions of aeolian sands in the active Bagnold dune field. The Bagnold sands are rounded to subrounded, very fine- to medium- sized (~45-500 µm) with ≥6 distinct grain colors. In contrast to sands examined by Curiosity in a dust-covered, inactive bedform called Rocknest and soils at other landing sites, Bagnold sands are darker, less red, better sorted, have fewer silt-sized or smaller grains, and show no evidence for cohesion. Nonetheless, Bagnold mineralogy and Rocknest mineralogy are similar with plagioclase, olivine, and pyroxenes in similar proportions comprisingmore » >90% of crystalline phases, along with a substantial amorphous component (35% ± 15%). Yet, Bagnold and Rocknest bulk chemistry differ. Bagnold sands are Si-enriched relative to other soils at Gale crater, and H 2O, S, and Cl are lower relative to all previously measured martian soils and most Gale crater rocks. Mg, Ni, Fe, and Mn are enriched in the coarse-sieved fraction of Bagnold sands, corroborated by VNIR spectra that suggest enrichment of olivine. Together, patterns in major element chemistry and volatile release data indicate two distinctive volatile reservoirs in martian soils: (1) amorphous components in the sand-sized fraction (represented by Bagnold) that are Si-enriched, hydroxylated alteration products and/or impact or volcanic glasses; and (2) amorphous components in the fine fraction (<40 µm; represented by Rocknest and other bright soils) that are Fe-, S-, and Cl-enriched with low Si and adsorbed and structural H 2O.« less
  • The Mars Science Laboratory rover Curiosity encountered potassium-rich clastic sedimentary rocks at two sites in Gale Crater, the waypoints Cooperstown and Kimberley. These rocks include several distinct meters thick sedimentary outcrops ranging from fine sandstone to conglomerate, interpreted to record an ancient fluvial or fluvio-deltaic depositional system. Furthermore, from ChemCam Laser-Induced Breakdown Spectroscopy (LIBS) chemical analyses, this suite of sedimentary rocks has an overall mean K 2O abundance that is more than 5 times higher than that of the average Martian crust. The combined analysis of ChemCam data with stratigraphic and geographic locations then reveals that the mean K 2Omore » abundance increases upward through the stratigraphic section. Chemical analyses across each unit can be represented as mixtures of several distinct chemical components, i.e., mineral phases, including K-bearing minerals, mafic silicates, Fe-oxides, and Fe-hydroxide/oxyhydroxides. Possible K-bearing minerals include alkali feldspar (including anorthoclase and sanidine) and K-bearing phyllosilicate such as illite. Mixtures of different source rocks, including a potassium-rich rock located on the rim and walls of Gale Crater, are the likely origin of observed chemical variations within each unit. Physical sorting may have also played a role in the enrichment in K in the Kimberley formation. The occurrence of these potassic sedimentary rocks provides additional evidence for the chemical diversity of the crust exposed at Gale Crater.« less
  • At Gale crater, Mars, ChemCam acquired its first laser-induced breakdown spectroscopy (LIBS) target on Sol 13 of the landed portion of the mission (a Sol is a Mars day).
  • The Chemistry Camera (ChemCam) instrument onboard Curiosity can detect minor and trace elements such as lithium, strontium, rubidium, and barium. Their abundances can provide some insights about Mars' magmatic history and sedimentary processes. We focus on developing new quantitative models for these elements by using a new laboratory database (more than 400 samples) that displays diverse compositions that are more relevant for Gale crater than the previous ChemCam database. These models are based on univariate calibration curves. For each element, the best model is selected depending on the results obtained by using the ChemCam calibration targets onboard Curiosity. New quantificationsmore » of Li, Sr, Rb, and Ba in Gale samples have been obtained for the first 1000 Martian days. Comparing these data in alkaline and magnesian rocks with the felsic and mafic clasts from the Martian meteorite NWA7533—from approximately the same geologic period—we observe a similar behavior: Sr, Rb, and Ba are more concentrated in soluble- and incompatible-element-rich mineral phases (Si, Al, and alkali-rich). Correlations between these trace elements and potassium in materials analyzed by ChemCam reveal a strong affinity with K-bearing phases such as feldspars, K-phyllosilicates, and potentially micas in igneous and sedimentary rocks. However, lithium is found in comparable abundances in alkali-rich and magnesium-rich Gale rocks. This very soluble element can be associated with both alkali and Mg-Fe phases such as pyroxene and feldspar. Here, these observations of Li, Sr, Rb, and Ba mineralogical associations highlight their substitution with potassium and their incompatibility in magmatic melts.« less
  • The Curiosity rover's campaign at Pahrump Hills provides the first analyses of lower Mount Sharp strata. We report ChemCam elemental composition of a diverse assemblage of post-depositional features embedded in, or cross-cutting, the host rock. ChemCam results demonstrate their compositional diversity, especially compared to the surrounding host rock: (i) Dendritic aggregates and relief enhanced features, characterized by a magnesium enhancement and sulfur detection, and interpreted as Mg-sulfates; (ii) A localized observation that displays iron enrichment associated with sulfur, interpreted as Fe-sulfate; (iii) Dark raised ridges with varying Mg- and Ca-enriched compositions compared to host rock; (iv) Several dark-toned veins withmore » calcium enhancement associated with fluorine detection, interpreted as fluorite veins. (v) Light-toned veins with enhanced calcium associated with sulfur detection, and interpreted as Ca-sulfates. The diversity of the Pahrump Hills diagenetic assemblage suggests a complex post-depositional history for fine-grained sediments for which the origin has been interpreted as fluvial and lacustrine. Assessment of the spatial and relative temporal distribution of these features shows that the Mg-sulfate features are predominant in the lower part of the section, suggesting local modification of the sediments by early diagenetic fluids. Conversely, light-toned Ca-sulfate veins occur in the whole section and cross-cut all other features. A relatively late stage shift in geochemical conditions could explain this observation. The Pahrump Hills diagenetic features have no equivalent compared to targets analyzed in other locations at Gale crater. Only the light-toned Ca-sulfate veins are present elsewhere, along Curiosity's path, suggesting they formed through a common late-stage process that occurred at over a broad area.« less