Amorphous zinc borate as a simple standard for baseline correction in Raman spectra

In this paper, our research group proposes a simple solution to a usual problem that appears in the Raman analysis of some substances, which is the presence of weak Raman signals, probably in combination with a high‐intensity luminescence background, affected by the presence of distortions in the baseline. Under this condition, the spectroscopist has to face spectra hard to edit and correct and thus hard to study. There are already some standard solutions that allow the correction of spectra from relative intensity to absolute intensity that also solves this problem and also allow quantitative analyses. But these solutions imply expensive standards or devices that could not be a worthy option when not working in absolute intensity or the Raman analyses stay at qualitative level and a quantitative study is not needed. The alternative Do It Yourself solution proposed in this paper is based on the use of amorphous zinc borate, an easy‐to‐find substance, which after a simple processing allows us to correct the baseline of Raman spectra qualitatively, offering a useful and economic reference when an absolute intensity correction is not needed. In order to evaluate the effectiveness of this procedure, some spectra were corrected using amorphous zinc borate and then compared the signal‐to‐noise ratio of some Raman signals before and after this correction. Copyright © 2017 John Wiley & Sons, Ltd.MINECO ESP2014-56138-C3-1-

Surface and microstructural failures of PET-Coated ECCS plates by salmon-polymer interaction

Producción CientíficaThe new types of knowledge-intensive, multilayer containers consist of steel plates protected against corrosion by nanometric electrolytic chromium (Cr0) and chromium oxide (Cr2O3) layers chemically bonded to polyethylene terephthalate (PET) polymer coating to preserve food. It was observed that after emptying the cans, the salmon adhered to the polymer coating, changing its color, and that this adhesion increased with longer storage times. This work was aimed at determining the product-container interactions and their characterization by X-ray diffraction (XRD), confocal Raman and micro-Raman imaging and scanning electron microscopy (SEM) analysis. The zones of adhesion showed surface changes, variations in crystallinity and microstructural degradation of the PET coating. In addition, localized damages altering the functional properties of the multilayer system were observed as microcracking in the chromium layers that protect the steel. The degradation undergone was evaluated and characterized at a surface and microstructural level to establish the failure mechanisms, which were mainly associated with the activity of the adhered muscle and its biochemical components. Finally, a recommendation is done to preserve the useful life and functionality of cans for the preservation and efficient use of resources with an impact on recycling and environmental conservancy.The authors gratefully acknowledge the Fondecyt Program of Conicyt Chile for the financial support through Grant No. 1130634 and the special contribution of University Austral of Chile

Survival of Moss Reproductive Structures under Simulated Martian Environmental Conditions and Extreme Thermal Stress: Vibrational Spectroscopic Study and Astrobiological Implications

The principal goal of astrobiology is the search for extraterrestrial life forms. A key aspect is the study of the ability of different kinds of terrestrial organisms to support simulated extraterrestrial environmental conditions. Mosses are multicellular green plants, poorly studied from an astrobiological perspective. In this paper, we report experimental results obtained using two species of moss, which demonstrate that both the spores of the moss Funaria hygrometrica as well as the desiccated vegetative gametophyte shoots of the moss Tortella squarrosa (=Pleurochaete squarrosa) were capable of resisting Simulated Martian Environmental Conditions (SMEC): Mars simulated atmospheric composition 99.9% CO2, and 0.6% H2O with a pressure of 7 mbars, -73 ºC and UV irradiation of 30 mW cm-2 in a wavelength range of 200-400 nm under a limited short time of exposition of 2 hours. After being exposed to SMEC and then transferred to an appropriate growth medium, the F. hygrometrica spores germinated, producing typical gametophyte protonemal cells and leafy shoots. Likewise, detached leaves from SMEC-exposed gametophyte shoots of T. squarrosa retained the ability to produce new protonemata and shoots under suitable growth conditions. Furthermore, we studied the tolerance of these moss structures to a thermal stress of 100 °C for 1 h; in both cases the spores and shoots were capable of resisting this heat treatment. Our study using FT-Raman and FT-IR vibrational spectroscopy demonstrated that neither spores nor shoots apparently suffered significant damage in their biomolecular makeup after being subject to these stress treatments. The implications of these findings for the search of life on Mars are discussed

In situ Raman characterization of minerals and degradation processes in a variety of cultural and geological heritage sites

Wetest the capabilities of in situ Raman spectroscopy for non-destructive analysis of degradation processes in invaluable masterpieces, as well as for the characterization of minerals and prehistoric rock-art in caves. To this end, we have studied the mechanism of decay suffered by the 15th-century limestone sculptures that decorate the retro-choir of Burgos Cathedral (N Spain). In situ Raman probe detected hydrated sulfate and nitrateminerals on the sculptures, which are responsible for the decay of the original limestone. In addition, in situ Raman analyses were performed on unique speleothems in El Soplao Cave (Cantabria, N Spain) and in the Gruta de las Maravillas (Aracena, SWSpain). Unusual cavemineralswere detected in El Soplao Cave, such as hydromagnesite (Mg5(CO3)4(OH)2·4H2O), as well as ferromanganese oxides in the black biogenic speleothems recently discovered in this cavern. In the Gruta de las Maravillas, gypsum (CaSO4·2H2O) was identified for the first time, as part of the oldest cave materials, so providing additional evidence of hypogenic mechanisms that occurred in this cave during earlier stages of its formation. Finally, we present preliminary analyses of several cave paintings in the renowned “Polychrome Hall” of Altamira Cave (Cantabria, N. Spain). Hematite (Fe2O3) is the most abundant mineral phase, which provides the characteristic ochre-reddish color to the Altamira bison and deer paintings. Thus, portable Raman spectroscopy is demonstrated to be an analytical technique compatible with preserving our cultural and natural heritage, since the analysis does not require physical contact between the Raman head and the analyzed items

Raman-Mössbauer-XRD studies of selected samples from “Los Azulejos” outcrop: A possible analogue for assessing the alteration processes on Mars

The outcrop of “Los Azulejos” is visible at the interior of the Cañadas Caldera in Tenerife Island (Spain). It exhibits a great variety of alteration processes that could be considered as terrestrial analogue for several geological processes on Mars. This outcrop is particularly interesting due to the content of clays, zeolite, iron oxides, and sulfates corresponding to a hydrothermal alteration catalogued as “Azulejos” type alteration. A detailed analysis by portable and laboratory Raman systems as well as other different techniques such as X ray diffraction (XRD) and Mössbauer spectroscopy has been carried out (using twin-instruments from Martian lander missions: Mössbauer spectrometer MIMOS-II from the NASA-MER mission of 2001 and the XRD diffractometer from the NASA-MSL Curiosity mission of 2012). The mineral identification presents the following mineral species: magnetite, goethite, hematite, anatase, rutile, quartz, gregoryite, sulphate (thenardite and hexahydrite), diopside, feldspar, analcime, kaolinite and muscovite. Moreover, the in-situ Raman and Micro-Raman measurements have been performed in order to compare the capabilities of the portable system specially focused for the next ESA Exo-Mars mission. The mineral detection confirms the sub-aerial alteration on the surface and the hydrothermal processes by the volcanic fluid circulations in the fresh part. Therefore, the secondary more abundant mineralization acts as the color agent of the rocks. Thus, the zeolite-illite group is the responsible for the bluish coloration, as well as the feldspars and carbonates for the whitish and the iron oxide for the redish parts. The XRD system was capable to detect a minor proportion of pyroxene, which is not visible by Raman and Mössbauer spectroscopy due to the “Azulejos” alteration of the parent material on the outcrop. On the other hand, Mössbauer spectroscopy was capable of detecting different types of iron-oxides (Fe3+/2+-oxide phases). These analyses emphasize the strength of the different techniques and the working synergy of the three different techniques together for planetary space missions.The work was supported by the MICINN with the Project AYA-2008-04529.Peer reviewe

ExoMars Raman Laser Spectrometer (RLS): development of chemometric tools to classify ultramafic igneous rocks on Mars

Producción CientíficaThis work aims to evaluate whether the multi-point analysis the ExoMars Raman Laser Spectrometer (RLS) will perform on powdered samples could serve to classify ultramafc rocks on Mars. To do so, the RLS ExoMars Simulator was used to study terrestrial analogues of Martian peridotites and pyroxenites by applying the operational constraints of the Raman spectrometer onboard the Rosalind Franklin rover. Besides qualitative analysis, RLS-dedicated calibration curves have been built to estimate the relative content of olivine and pyroxenes in the samples. These semi-quantitative results, combined with a rough estimate of the concentration ratio between clino- and ortho-pyroxene mineral phases, were used to classify the terrestrial analogues. XRD data were fnally employed as reference to validate Raman results. As this preliminary work suggests, ultramafc rocks on Mars could be efectively classifed through the chemometric analysis of RLS data sets. After optimization, the proposed chemometric tools could be applied to the study of the volcanic geological areas detected at the ExoMars landing site (Oxia Planum), whose mineralogical composition and geological evolution have not been fully understoodProyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-RProyecto MINECO Retos de la Sociedad. Ref. ESP2017-87690-C3-1-

Insights into speleothems from lava tubes of the Galapagos Islands (Ecuador): mineralogy and biogenecity

Different types of hard and soft speleothems (stalactites, stalagmites, columns, crusts, flowstones, micro-gours and botryoidal coralloids) have been observed throughout lava tubes in the Galapagos archipelago, Ecuador. Three lava tubes were studied in this work: Gallardo and Royal Palm volcanic caves (Santa Cruz Island) and Sucre Cave (Isabela Island). The studied speleothems were mainly formed by opal, calcite and clay minerals, including plagioclase and pyroxenes from the basaltic host rock. Rarely, iron oxides, gypsum were found in some speleothems, which were interpreted as alteration products of the primary volcanic materials. Field emission scanning electron microscopy revealed abundant filamentous 17th International Vulcanspeleology Symposium 2 bacteria, and reticulated filaments similar to those recently observed in others lava tubes around the world. These filaments are associated with EPS and mineral deposits rich in Si, Ca or Fe. The identified minerals and the evidence of biosignatures suggest a biological contribution to speleothem development within Gallardo, Royal Palm and Sucre lava tubes

Semi‐quantification of binary saline solutions by Raman spectroscopy: Implications for Europa

Producción CientíficaThe Europa lander is a concept for a potential future planetary exploration mission which purpose is to characterize the icy shell of Europa and to search for organics. To achieve this objective, the current concept of the lander includes a Raman spectrometer, such as RLS instrument, that could be able to analyze (sub) surface targets in their solid and liquid form. Knowing that ice and brines of Europa are potentially enriched by sulfate and chlorides, this work seeks to evaluate if Raman spectroscopy could be used to semi quantify the saline content of water solutions using space-like instrumentation. To do so, MgSO4 and MgCl2 were used to prepare three sets of water solutions. Raman analyses were then performed by the laboratory simulator of the ExoMars Raman Laser Spectrometer (RLS), which has been defined as the threshold system for the Europa Lander. After data analysis, two different semi-quantification approaches were tested, and their results compared. Although univariate calibration curves proved to successfully quantify the content of SO42− and Cl− anions dissolved in mono-analyte water solutions, this strategy provided very poor results when applied to binary saline mixtures. Overcoming this issue, the non-linearity prediction ability of Artificial Neural Networks (ANNs) in combination with bandfitting allows to successfully resolve the complexity of the vibrational perturbation suffered by the OH region, which is caused by the cross interaction of H2O molecules with different anions.Ministerio de Economía y Competitividad, Grant/Award Number: PID2019-107442RBC31

Raman semi-quantification on Mars: ExoMars RLS system as a tool to better comprehend the geological evolution of martian crust

Producción CientíficaThis work presents the latest chemometric tools developed by the RLS science team to optimize the scientific outcome of the Raman system onboard the ExoMars 2022 rover. Feldspar, pyroxene and olivine samples were first analyzed through the RLS ExoMars Simulator to determine the spectroscopic indicators to be used for a proper discrimination of mineral phases on Mars. Being the main components of Martian basaltic rocks, lepidocrocite, augite and forsterite were then used as mineral proxies to prepare binary mixtures. By emulating the operational constraints of the RLS, Raman datasets gathered from laboratory mixtures were used to build external calibration curves. Providing excellent coefficients of determination (R2 0.9942÷0.9997), binary curves were finally used to semi-quantify ternary mixtures of feldspar, pyroxene and olivine minerals. As Raman results are in good agreement with real concentration values, this work suggests the RLS could be effectively used to perform semi-quantitative mineralogical studies of the basaltic geological units found at Oxia Planum. As such, crucial information about the geological evolution of Martian Crust could be extrapolated. In light of the outstanding scientific impact this analytical method could have for the ExoMars mission, further methodological improvements to be discussed in a dedicated work are finally proposed.Consejo Europeo de Investigación (grant 687302)Ministerio de Economía, Industria y Competitividad (grants PID2019-107442RB-C31 and RDE2018-102600-T

Application of chemometrics on Raman spectra from Mars: Recent advances and future perspectives

Producción CientíficaThe SuperCam and SHERLOC instruments onboard the NASA/Perseverancerover are returning the first Raman spectra to be ever collected from anotherplanet. Similarly, the RLS instrument onboard the ESA/Rosalind Franklinrover will collect Raman spectra from powdered rocks sampled from thesubsurface of Mars. To optimize the scientific exploitation of Raman spectrareturned from planetary exploration missions, tailored chemometric tools arebeing developed that take into account the analytical capability of the men-tioned Raman spectrometers. In this framework, the ERICA research groupis using laboratory simulators of SuperCam and RLS to perform representa-tive laboratory studies that will enhance the scientific outcome of bothMars2020 and ExoMars missions. On one hand, preliminary studies provedthe chemometric analysis of RLS datasets could be used to obtain a reliablesemi-quantitative estimation of the main mineral phases composing Martiangeological samples. On the other hand, it was proved the data fusion ofRaman and LIBS spectra gathered by SuperCam could be used to enhancethe discrimination of mineral phases from remote geological targets. Besidesdescribing the models developed by the ERICA group, this work presents anoverview of the complementary chemometric approaches so far tested in thisfield of study and propose further improvements to be addressed in thefuture.Ministerio de Economía y Competitividad, Beca/Concesión Número:PID2019-107442RBC31European Union’s Horizon 2020 research and innovation program. grant agreement no. 68730