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Modeling near-infrared reflectance spectra of clay and sulfate mixtures and implications for Mars

Stack, K. M. and Milliken, R. E. (2015) Modeling near-infrared reflectance spectra of clay and sulfate mixtures and implications for Mars. Icarus, 250 . pp. 332-356. ISSN 0019-1035.

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High-resolution mapping by visible and near-infrared orbital spectrometers has revealed a diversity of hydrated mineral deposits on the surface of Mars. Quantitative analysis of mineral abundances within these deposits has the potential to distinguish depositional and diagenetic processes. Such analysis can also provide important constraints on the nature of putative global and local-scale mineralogical transitions on Mars. However, the ability of models to extract quantitative mineral abundances from spectra of mixtures relevant to sedimentary rocks remains largely untested. This is particularly true for clay and sulfate minerals, which often occur as fine-grained components of terrestrial sedimentary rocks and are known to occur in a number of sedimentary deposits on Mars. This study examines the spectral properties of a suite of mixtures containing the Mg-sulfate epsomite mixed with varying proportions of smectitic clay (saponite, nontronite, and montmorrilonite). The goal of this work is to test the ability of checkerboard (linear) and intimate (non-linear) mixing models to obtain accurate estimates of mineral abundances under ideal and controlled laboratory conditions. The results of this work suggest that: (1) spectra of clay–sulfate mixtures can be reproduced by checkerboard and intimate mixing models to within 2% absolute reflectance or single scattering albedo, (2) clay and epsomite abundance can be modeled to within 5 wt.% when particle diameter is optimized, and (3) the lower threshold for modeling clay in spectra of clay–epsomite mixtures is approximately 10 wt.%, below which the models often fail to recognize the presence of clay.

Item Type:Article
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Stack, K. M.0000-0003-3444-6695
Milliken, R. E.0000-0003-3240-4918
Additional Information:© 2014 Elsevier Inc. Received 27 May 2014; Revised 4 December 2014; Accepted 7 December 2014; Available online 16 December 2014. George Rossman and Elizabeth Miura-Boyd are gratefully acknowledged for assisting with FTIR analysis and Thomas Bristow is thanked for his help in obtaining several of the clay mineral standards used in this study. This manuscript was greatly improved by comments from Christina Viviano-Beck and an anonymous reviewer. This work was funded by a NASA grant (Award # JPL.1271814) and a NASA Astrobiology Institute grant (MIT Subaward # 5710002515) to J. Grotzinger.
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Subject Keywords:Mars, surface; Spectroscopy; Infrared observations
Record Number:CaltechAUTHORS:20150112-080233651
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Official Citation:K.M. Stack, R.E. Milliken, Modeling near-infrared reflectance spectra of clay and sulfate mixtures and implications for Mars, Icarus, Volume 250, April 2015, Pages 332-356, ISSN 0019-1035, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:53542
Deposited By: Tony Diaz
Deposited On:13 Jan 2015 01:57
Last Modified:09 Mar 2020 13:19

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