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Title: Constraints on iron sulfate and iron oxide mineralogy from ChemCam visible/near-infrared reflectance spectroscopy of Mt. Sharp basal units, Gale Crater, Mars

Relative reflectace point spectra (400–840 nm) were acquired by the Chemistry and Camera (ChemCam) instrument on the Mars Science Laboratory (MSL) rover Curiosity in passive mode (no laser) of drill tailings and broken rock fragments near the rover as it entered the lower reaches of Mt. Sharp and of landforms at distances of 2–8 km. Freshly disturbed surfaces are less subject to the spectral masking effects of dust, and revealed spectral features consistent with the presence of iron oxides and ferric sulfates. Here, we present the first detection on Mars of a ~433 nm absorption band consistent with small abundances of ferric sulfates, corroborated by jarosite detections by the Chemistry and Mineralogy (CheMin) X-ray diffraction instrument in the Mojave, Telegraph Peak, and Confidence Hills drilled samples. The disturbed materials near the Bonanza King region also exhibited strong 433 nm bands and negative near-infrared spectral slopes consistent with jarosite. ChemCam passive spectra of the Confidence Hills and Mojave drill tailings showed features suggestive of the crystalline hematite identified by CheMin analyses. The Windjana drill sample tailings exhibited flat, low relative reflectance spectra, explained by the occurrence of magnetite detected by CheMin. Passive spectra of Bonanza King were similar, suggesting the presencemore » of spectrally dark and neutral minerals such as magnetite. Long-distance spectra of the “Hematite Ridge” feature (3–5 km from the rover) exhibited features consistent with crystalline hematite. The Bagnold dune field north of the Hematite Ridge area exhibited low relative reflectance and near-infrared features indicative of basaltic materials (olivine, pyroxene). Light-toned layers south of Hematite Ridge lacked distinct spectral features in the 400–840 nm region, and may represent portions of nearby clay minerals and sulfates mapped with orbital near-infrared observations. The presence of ferric sulfates such as jarosite in the drill tailings suggests a relatively acidic environment, likely associated with flow of iron-bearing fluids, associated oxidation, and/or hydrothermal leaching of sedimentary rocks. Combined with other remote sensing data sets, mineralogical constraints from ChemCam passive spectra will continue to play an important role in interpreting the mineralogy and composition of materials encountered as Curiosity traverses further south within the basal layers of the Mt. Sharp complex.« less
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [4] ;  [4] ;  [6] ;  [7] ;  [8] ;  [9] ;  [10] ;  [3] ; ORCiD logo [11]
  1. Johns Hopkins Univ., Laurel, MD (United States)
  2. Arizona State Univ., Tempe, AZ (United States)
  3. Planetary Science Inst., Tucson, AZ (United States)
  4. California Inst. of Technology (CalTech), Pasadena, CA (United States). Jet Propulsion Lab.
  5. Univ. of Winnipeg, MB (Canada)
  6. Univ. of Toulouse (France). Inst. for Research in Astrophysics and Planetology (IRAP), National Centre for Scientific Research (CNRS)
  7. Univ. of Copenhagen (Denmark). The Niels Bohr Inst.
  8. Univ. of Nantes (France). Lab. of Planetology and Geodynamics
  9. Univ. of Toulouse (France). Institute for Research in Astrophysics and Planetology (IRAP). National Centre for Scientific Research (CNRS)
  10. NASA Johnson Space Center, Houston, TX (United States)
  11. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0003-004X
Grant/Contract Number:
AC52-06NA25396; 1350588
Accepted Manuscript
Journal Name:
American Mineralogist
Additional Journal Information:
Journal Volume: 101; Journal Issue: 7; Journal ID: ISSN 0003-004X
Mineralogical Society of America
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
National Aeronautics and Space Administration (NASA)
Country of Publication:
United States
58 GEOSCIENCES; Planetary Sciences
OSTI Identifier: