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ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars

Johnson, Jeffrey R. and Bell, J. F., III and Bender, S. and Blaney, D. and Cloutis, E. and DeFlores, L. and Ehlmann, B. and Gasnault, O. and Gondet, B. and Kinch, K. and Lemmon, M. and Le Mouélic, S. and Maurice, S. and Rice, M. and Wiens, R. C. (2015) ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars. Icarus, 249 . pp. 74-92. ISSN 0019-1035.

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The spectrometers on the Mars Science Laboratory (MSL) ChemCam instrument were used in passive mode to record visible/near-infrared (400–840 nm) radiance from the martian surface. Using the onboard ChemCam calibration targets’ housing as a reflectance standard, we developed methods to collect, calibrate, and reduce radiance observations to relative reflectance. Such measurements accurately reproduce the known reflectance spectra of other calibration targets on the rover, and represent the highest spatial resolution (0.65 mrad) and spectral sampling (<1 nm) visible/near-infrared reflectance spectra from a landed platform on Mars. Relative reflectance spectra of surface rocks and soils match those from orbital observations and multispectral data from the MSL Mastcam camera. Preliminary analyses of the band depths, spectral slopes, and reflectance ratios of the more than 2000 spectra taken during the first year of MSL operations demonstrate at least six spectral classes of materials distinguished by variations in ferrous and ferric components. Initial comparisons of ChemCam spectra to laboratory spectra of minerals and Mars analog materials demonstrate similarities with palagonitic soils and indications of orthopyroxene in some dark rocks. Magnesium-rich “raised ridges” tend to exhibit distinct near-infrared slopes. The ferric absorption downturn typically found for martian materials at <600 nm is greatly subdued in brushed rocks and drill tailings, consistent with their more ferrous nature. Calcium-sulfate veins exhibit the highest relative reflectances observed, but are still relatively red owing to the effects of residual dust. Such dust is overall less prominent on rocks sampled within the “blast zone” immediately surrounding the landing site. These samples were likely affected by the landing thrusters, which partially removed the ubiquitous dust coatings. Increased dust coatings on the calibration targets during the first year of the mission were documented by the ChemCam passive measurements as well. Ongoing efforts to model and correct for this dust component should improve calibration of the relative reflectance spectra. This will be useful as additional measurements are acquired during the rover’s future examinations of hematite-, sulfate-, and phyllosilicate-bearing materials near the base of Mt. Sharp that are spectrally active in the 400–840 nm region.

Item Type:Article
Related URLs:
URLURL TypeDescription
Johnson, Jeffrey R.0000-0002-5586-4901
Bell, J. F., III0000-0002-2006-4074
Blaney, D.0000-0002-4267-7939
Cloutis, E.0000-0001-7301-0929
Ehlmann, B.0000-0002-2745-3240
Gasnault, O.0000-0002-6979-9012
Rice, M.0000-0002-8370-4139
Wiens, R. C.0000-0002-3409-7344
Additional Information:© 2014 Elsevier Inc. Received 8 October 2013; Revised 5 February 2014; Accepted 23 February 2014; Available online 13 March 2014. The authors wish to thank the entire engineering and science teams who were integral in landing the Curiosity rover successfully, and in operating a complicated science instrument package efficiently to maximize the science return. In particular, the diligence of the downlink and uplink teams is truly appreciated, as is the generosity of the ChemCam team in agreeing to use the instrument in a manner distinct from its main purpose. The results demonstrated the excellent sensitivity of the instrument’s spectrometers and the benefits of flexibility when operating instruments on Mars. K. Seelos (JHU/APL) provided the CRISM spectrum, and A. Ody (Université Paris-Sud, Orsay, France) provided the bright and dark OMEGA spectra. S. Clegg (LANL) provided the list of ChemCam targets assigned to specific geologic units. Helpful reviews were provided by M. Lane and an anonymous reviewer. J.R. Johnson was funded by the Mars Science Laboratory Participating Scientist program. The French contribution to MSL is supported by the Centre National d’Etudes Spatiales (CNES). Work by K. Kinch was supported by the Danish Council for Independent Research/Natural Sciences (FNU Grant 12-127126).
Funding AgencyGrant Number
Mars Science Laboratory Participating Scientist ProgramUNSPECIFIED
Centre National d’Études Spatiales (CNES)UNSPECIFIED
Danish Council for Independent Research-Natural Sciences12-127126
Subject Keywords:Mars; Mars, surface; Spectroscopy
Record Number:CaltechAUTHORS:20141218-112209706
Persistent URL:
Official Citation:Jeffrey R. Johnson, J.F. Bell III, S. Bender, D. Blaney, E. Cloutis, L. DeFlores, B. Ehlmann, O. Gasnault, B. Gondet, K. Kinch, M. Lemmon, S. Le Mouélic, S. Maurice, M. Rice, R.C. Wiens, MSL Science Team, ChemCam passive reflectance spectroscopy of surface materials at the Curiosity landing site, Mars, Icarus, Volume 249, 15 March 2015, Pages 74-92, ISSN 0019-1035, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53020
Deposited By: Tony Diaz
Deposited On:18 Dec 2014 19:34
Last Modified:09 Mar 2020 13:19

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