¹Javier Cuadros, ¹Joe R. Michalski, ²Vesselin Dekov, ³Janice L. Bishop
¹Department of Earth Sciences, Natural History Museum, Cromwell Road, London SW7 5BD, U.K.
²Laboratoire de Géochimie et Métallogénie, Département Géosciences Marines, IFREMER, Z.I. Pointe du diable, BP 70, 29280 Plouzané, France
³SETI Institute, Mountain View, California 94043, U.S.A.

With the arrival of Curiosity on Mars, the MSL has started its ground validation of some of the phyllosilicate characterization carried out with remote sensing near-IR spectroscopy from orbital instruments. However, given the limited range of action of the rover, phyllosilicate identification and characterization will have to rely mainly on orbital near-IR data. Investigation of Earth analogs can greatly assist interpretation of martian spectra and enable more robust analyses. In this contribution, Mg/Fe-rich clays from submarine hydrothermal origin that had been thoroughly characterized previously were investigated with near-IR reflectance spectroscopy. The clays are mixed-layer glauconite-nontronite, talc-nontronite, talc-saponite, and nontronite samples. The hydroxyl bands in the range 2.1–2.35 μm were decomposed into their several individual components to investigate correlations between the octahedral chemistry of the samples and the normalized intensity of several bands. Good correlations were found for the samples of exclusive dioctahedral character (glauconite-nontronite and nontronite), whereas poor or no correlations emerged for the samples with one (talc-nontronite) or two (talc-saponite) trioctahedral layer components, indicating a more complex spectral response. Because these bands analyzed are a combination of the fundamental OH stretching and OH bending vibrations, the response of these fundamental bands to octahedral chemistry was considered. For 2:1 dioctahedral phyllosilicates, Fe and Mg substitution for Al displaces both fundamental bands to lower wavenumbers (longer wavelengths), so that their effect on the position of the combination band is coherent. In contrast, for trioctahedral clays, Al and Fe3+ substitution of octahedral Mg displaces the OH stretching band to lower wavenumber values, and the OH bending band to higher wavenumber values, resulting in partial or total mutual cancelation of their effects. As a result, clays with near-IR spectra indicating Mg-dominated octahedral compositions may in fact contain abundant Fe and some Al substitution. Thus, remote-sensing near-IR mineralogical and chemical identification of clays on Mars appears relatively straightforward for dioctahedral clay minerals but more problematic for trioctahedral clays, for which it may require a more detailed investigation of their near-IR spectra.

Reference
Cuadros J, Michalski JR, Dekov V, Bishop JL (2016) Octahedral chemistry of 2:1 clay minerals and hydroxyl band position in the near-infrared: Application to Mars. American Mineralogist 101, 554-563
Link to Article [doi:10.2138/am-2016-5366]
Copyright: The Mineralogical Society of America

¹Christopher D. K. Herd, ²Robert W. Hilts, ²Aaron W. Skelhorne,¹Danielle N. Simkus
¹Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, Alberta, Canada
²Department of Physical Sciences, MacEwan University, Edmonton, Alberta, Canada

The curation and handling of volatile-bearing astromaterials is of prime importance in current and future plans for sample return missions to targets containing organic compounds, ices, or other volatile components. We report on the specific curation constraints required for the preservation of the Tagish Lake meteorite, a C2 ungrouped chondrite that contains significant concentrations of organic matter, including compounds of prebiotic interest or volatile in character, and which was recovered from a frozen lake surface a few days after its fall. Here, we review the circumstances of the meteorite’s handling, its complement of intrinsic and contaminant organic compounds, and an unusual reaction between some of the specimens and the Al foil in which they were enclosed. From our results, we derive the requirements for curation of the meteorite, and describe a specialized facility that enables its curation and handling. The Subzero Facility for Curation of Astromaterials consists of a purified Ar glove box enclosed within a freezer chamber, and enables investigations relevant to curation of samples at or below −10 °C. We provide several recommendations based on insights obtained from the commissioning and initial use of the facility that are relevant to collection of freshly fallen meteorites, curation of volatile-bearing meteorites and other astromaterials, and planning and implementation of curation plans for future sample return missions to volatile-bearing targets.

Reference
Herd CDK, Hilts RW, Skelhorne AW, Simkus DN (2016) Cold curation of pristine astromaterials: Insights from the Tagish Lake meteorite. Meteoritics & Planetary Science (in Press)
Link to Article [DOI: 10.1111/maps.12603]
Published by arrangement with John Wiley & Sons