¹P. A. Bland,²G. S. Collins,²T. M. Davison,³N. M. Abreu,⁴F. J. Ciesla,²A. R. Muxworthy, ²J. Moore
¹Department of Applied Geology, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia
²Impacts & Astromaterials Research Centre (IARC), Department of Earth Science & Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, UK
³Earth Science Program, Pennsylvania State University—Du Bois Campus, Du Bois, Pennsylvania 15801, USA N. M. Abreu
⁴Department of Geophysical Science, University of Chicago, 5734 South Ellis Avenue, Chicago, Illinois 60430, USA

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Reference
Bland PA, Collins GS, Davison TM, Abreu NM, Ciesla FJ, Muxworthy AR, Moore J (2014) Pressure–temperature evolution of primordial solar system solids during impact-induced compaction. Nature Communications 5, 5451
Link to Article [doi:10.1038/ncomms6451]

¹K.M. Stack, ²R.E. Milliken
¹Department of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
²Department of Geological Sciences, Brown University, Providence, RI, 02912

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.

Reference
Stack KM, Milliken RE (2014) Modeling near-infrared reflectance spectra of clay and sulfate mixtures and implications for Mars. Icarus (in Press)
Link to Article [doi:10.1016/j.icarus.2014.12.009]

Copyright Elsevier

¹Christopher R. Webster et al. (>10)*
¹Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.
*Find the extensive, full author and affiliation list on the publishers website

Reports of plumes or patches of methane in the Martian atmosphere that vary over monthly timescales have defied explanation to date. From in situ measurements made over a 20-month period by the Tunable Laser Spectrometer (TLS) of the Sample Analysis at Mars (SAM) instrument suite on Curiosity at Gale Crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 ppbv at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet (UV) degradation of accreted interplanetary dust particles (IDP’s) or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period, we observed elevated levels of methane of 7.2 ± 2.1 (95% CI) ppbv implying that Mars is episodically producing methane from an additional unknown source.

Reference
Webster CR et al. (2014) Mars methane detection and variability at Gale crater. Science (in Press)
Link to Article [Science DOI: 10.1126/science.1261713]

Reprinted with permission from AAAS