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Phyllosilicates, one of the five major structural types of silicates, have highly variable structures and very complex chemistry. This manuscript reports the first comprehensive Raman spectroscopic study of the five major groups of phyllosilicates. We first demonstrate that phyllosilicates have a unique Raman spectral pattern that can be used to distinguish them from orthosilicate, chain silicate, ring silicate, and framework silicate with different degrees of silicate polymerization. Second, we distinguish characteristics of Raman spectral features associated with phyllosilicates of the different stacking sequences and show how minor changes in chemical compositions and structural details in some phyllosilicates can affect their Raman spectral patterns, peak positions, and peak widths. From this study, we extract several empirical rules that can help to identify and characterize phyllosilicates based on in situ Raman spectroscopic measurements. These results are significant for planetary surface exploration, especially Mars, where the existence of phyllosilicates as a result of alteration of primary minerals has been indicated by Vis-Near IR spectroscopy used in orbital remote sensing and recently by X-ray diffraction in surface exploration. The spectral data collected from this study are also useful for laboratory study of terrestrial phyllosilicate samples. Copyright © 2015 John Wiley & Sons, Ltd.

Ferric sulfates with various hydration degrees were found on Mars by surface exploration and orbital remote sensing. The processes that they experienced during their formation and alteration relate to Martian hydrologic history and thus have been important topics for laboratory investigations. This study reports three sets of dehydration experiments conducted on Na-jarosite, ferricopiapite, and rhomboclase under two relative humidity conditions (5–6% RH and 10–11% RH) at two temperatures (50 and 95 °C), for which laser Raman spectroscopy and gravimetric measurements were the only two techniques used, in situ and non-invasively, to monitor the progress of these experiments. Our dehydration experiments show that OH-bearing Na-jarosite is relatively stable at 95 °C and RH

Laser Raman spectroscopy (LRS) has been proposed for in situ characterization of molecular species in planetary surface exploration, and three laser Raman spectrometers are included in the science payloads of two under-development missions to Mars (ESA-ExoMars2018 and NASA-Mars2020). We report the first rover test of a laser Raman spectrometer developed for flight, the Mars Micro-beam Raman Spectrometer (MMRS) in the Atacama Desert (Chile). The MMRS was integrated on the Zoe rover and analyzed subsurface samples brought up by a 1 m drill and delivered by a carousel. The MMRS demonstrated robust performance over 50-km traverse on rugged terrains. From MMRS data, igneous minerals, carbonates, sulfates and carbonaceous materials were unambiguously identified. Quantified distributions of major minerals and carbonaceous materials are extracted from MMRS results, which can be used to imply the regional geological evolution, and potential bioactivities. MMRS in the field performed as well as an LRS laboratory instrument when MMRS was focused satisfactorily. The discovery of stable γ-anhydrite, in large quantity (20% in a sample), in the Atacama soils raises an important question of its stability in the field in a natural environment that is worth further laboratory experimental investigation. Copyright © 2015 John Wiley & Sons, Ltd.

A planetary environment and analysis chamber (PEACh) has been developed at Washington University in St. Louis, in order to perform in situ multiple spectroscopic measurements on geological samples under relevant planetary environmental conditions and to support future planetary missions, with particular interest on Mars. The pressure in the chamber can range from ambient to 3 × 10−2 mbar. The simulated atmospheric composition and pressure are regulated via a combination of needle and ball valves connecting the chamber with containers filled with premixed gas. The temperature of the samples can be controlled in a range from ambient to − 100 °C. The in situ analytical techniques implemented (and to be implemented) are laser Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), near-IR reflectance spectroscopy, mid-IR attenuated total reflectance spectroscopy, and microscopic imaging. The coordinated spectroscopic sensing on the same geological sample under well-controlled atmospheric conditions in the PEACh establishes a way to link the results from the laboratory experiments to the spectral data obtained by landed and orbital planetary exploration missions, which will facilitate understanding the surface processes by which mineral phases occur and their association with atmospheric changes. Copyright © 2011 John Wiley & Sons, Ltd.

The identification of iron sulfates on Mars by the Mars Exploration Rovers (MERs) and the Mars Reconnaissance Orbiter emphasized the importance of studying iron sulfates in laboratory simulation experiments. The copiapite group of minerals was suggested as one of the potential iron sulfates occurring on the surface and subsurface on Mars, so it is meaningful to study their spectroscopic features, especially the spectral changes caused by cation substitutions. Four copiapite samples with cation substitutions (Fe3+, Al3+, Fe2+, Mg2+) were synthesized in our laboratory. Their identities were confirmed by powder X-ray diffraction (XRD). Spectroscopic characterizations by Raman, mid-IR, vis-NIR and laser-induced-breakdown spectroscopy (LIBS) were conducted on those synthetic copiapite samples, as these technologies are being (and will be) used in current (and future) missions to Mars. We have found a systematic ν1peak shift in the Raman spectra of the copiapite samples with cation substitutions, a consistent atomic ratio detection by LIBS, a set of systematic XRD line shifts representing structural change caused by the cation substitutions and a weakening of selection rules in mid-IR spectra caused by the low site symmetry of (SO4)2− in the copiapite structures. The near-infrared (NIR) spectra of the trivalent copiapite species show two strong diagnostic water features near 1.4 and 1.9 µm, with two additional bands near 2.0 µm. In the vis-NIR spectra, the position of an electronic band shifts from 0.85 µm for ferricopiapite to 0.866 µm for copiapite, and this shift suggests the appearance of a Fe2+ electronic transition band near 0.9 µm. Copyright © 2010 John Wiley & Sons, Ltd.

Using the Raman point-count procedure that we anticipate using in planetary surface exploration, we have identified and characterized the major, minor and trace mineral phases in rock chips of a Martian meteorite, EETA 79001. Raman spectra are shown for pyroxene, olivine, maskelynite (shocked, isotropized feldspar), chromite, magnetite, ilmenite, ulvospinel, pyroxferroite, merrillite, apatite, anatase, an Fe sulfide, calcite and hematite. Raman spectra provide information on compositional variations of pyroxene, olivine and FeTiCr oxides and modal proportions of the rock. The maskelynite-free mineral mode obtained on rough rock surfaces is consistent with modes obtained by optical microscopy on a thin section of lithology A of this meteorite. Compositions and variations in compositions of major silicate minerals (pyroxene and olivine) on the basis of Raman peak positions are consistent with those obtained in previous studies by electron probe microanalysis. The variations in composition of the silicate minerals represent different stages of crystallization during the formation of this rock near the Martian surface. Copyright © 2004 John Wiley & Sons, Ltd.