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Clays are fine‐grained rocks that form in the presence of water. Their occurrence typically depends on a combination of geological setting and geochemical conditions. The widespread and diverse clay deposits identified on Mars indicate that the planet experienced multiple episodes of water activity, especially in the early period. The characterisation of Martian clays will reveal key information on geological history, the past climatic conditions and the overall habitability of Mars. Among the analytical techniques typically utilised for such mineralogical characterisation, Raman spectroscopy will be applied for the first time during several robotic exploration missions of Mars in the 2020s. In this study, various clay‐rich samples from Westerwald, Germany were analysed to help inform mission operations and interpretation of data returned by the miniaturised Raman instruments. The samples, as verified by infrared spectroscopy, constitute kaolinites, Al‐rich smectites and Fe/Mg‐rich smectites, which are relevant to the clay mineralogy expected at Martian landing sites (Jezero crater and Oxia Planum). Despite the levels of fluorescence experienced during Raman measurements of the clay‐rich powder samples when using a 532 nm laser, the Raman signatures of phyllosilicates were identified for kaolinite and several different types of smectite (e.g. montmorillonite, nontronite, saponite) in these complex dispersions. Following these measurements, identification of various accessory minerals disseminated in the clay matrix was also achieved using the micro‐Raman system. Finally, a brief discussion concerning the analytical strategies for successful clay analyses using miniaturised Raman instruments is provided. [ABSTRACT FROM AUTHOR]

The scientific aims of the ExoMars Raman laser spectrometer (RLS) include identifying biological signatures and evidence of mineralogical processes associated with life. The RLS instrument was optimised to identify carbonaceous material, including reduced carbon. Previous studies suggest that reduced carbon on the Martian surface (perhaps originating from past meteoric bombardment) could provide a feedstock for microbial life. Therefore, its origin, form, and thermal history could greatly inform our understanding of Mars' past habitability. Here, we report on the Raman analysis of a Nakhla meteorite analogue (containing carbonaceous material) that was subjected to shock through projectile impact to simulate the effect of meteorite impact. The characterisation was performed using the RLS Simulator, in an equivalent manner to that planned for ExoMars operations. The spectra obtained verify that the flight‐representative system can detect reduced carbon in the basaltic sample, discerning between materials that have experienced different levels of thermal processing due to impact shock levels. Furthermore, carbon signatures acquired from the cratered material show an increase in molecular disorder (and we note that this effect will be more evident at higher levels of thermal maturity). This is likely to result from intense shearing forces, suggesting that shock forces within basaltic material may produce more reactive carbon. This result has implications for potential (past) Martian habitability because impacted, reduced carbon may become more biologically accessible. The data presented suggest the RLS instrument will be able to characterise the contribution of impact shock within the landing site region, enhancing our ability to assess habitability. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is a commonly applied technique for identifying the molecular nature of the constituents of solid samples. However, the quantification of the intensity associated with a particular molecular solute in solid dispersions requires analytical strategies to integrate the possible microheterogeneity in terms of composition. Many quantitative applications of solid dispersions rely on large spectral datasets. However, analytical procedures with limited data acquisition must be developed in preparation for future robotic planetary exploration missions or for field applications on earth, both of which involve miniaturised instrumentation. Based on statistical models, we evaluate the minimum number of spectra required to deliver robust data for quantitative measurements associated with differing concentrations of β‐carotene or L‐cysteine dispersed in gypsum. In this respect, reference materials were prepared, and we investigated an analytical methodology based on a large, automated multipoint scanning approach enabling the representative interrogation of the samples. We demonstrate from a comprehensive and reproducible model that the intensity associated with different organic contents within a mineral matrix can be estimated from a reduced number of spectra. Calibration curves were established for our reference dispersions of L‐cysteine in gypsum in the range 1–10 wt%, using both confocal benchtop and nonconfocal miniaturised portable instruments. We propose a reference system and a Raman analytical strategy, that is, adaptable for planetary exploration constraints, and which allows quantitative comparison of performance of instrumentation in terms of signal detection. [ABSTRACT FROM AUTHOR]

The Raman Laser Spectrometer (RLS) is one of the three Pasteur Payload instruments located within the rover analytical laboratory drawer (ALD), for ESA's Aurora exploration programme, ExoMars 2020 mission. The instrument will analyse the crushed surface and subsurface samples that are positioned below the Raman optical head by the ALD carousel. The RLS engineering and qualification model (EQM) was delivered to ESA at the end of 2017, after a wide technical and scientific test characterization campaign. The scientific campaign comprised instrument calibration and detailed evaluation of the scientific requirements and overall performance. For spectral calibration, continuous emission standard lamps (such as Hg‐Ar, Ne, and Xe) were utilized, as well as Raman spectra of pure liquids typically used as standards (cyclohexane and carbon tetrachloride (CCl4)). In addition, Raman spectra of the RLS calibration target (CT), a small disc of polyethylene terephthalate (PET) were obtained at various temperatures. This target, placed inside the rover, will be used for both Instrument health checks and calibration activities throughout Mars operations. For the scientific requirements and performance evaluations, several liquid and solid samples were analysed under a wide range of ambient conditions. The obtained spectral band parameters (peak position, relative peak intensity, peak width, and peak profile) were evaluated. Also, the instrument response (in terms of SNR) was characterized at different integration times and detector operating temperatures. In this paper, we provide a description of the development, verification, functional test, and overall scientific performance of the RLS instrument developed for ExoMars. Particular attention is placed on the performance of the EQM, which is the most representative instrument, in terms of engineering and functionality, of the flight model (FM) and in addition is used for performing all the mechanical, thermal, and radiation tests necessary for space qualification (for planetary applications). The data presented and analysed here, comprise part of the overall dataset obtained during the full instrument characterization campaign conducted at INTA before and during delivery and integration of the EQM in the rover ALD at TAS‐I facilities (Torino, Italy). The results obtained confirm that the full functionality and scientific performance of the RLS instrument was maintained after integration. [ABSTRACT FROM AUTHOR]

Raman spectroscopy has been identified as a powerful tool for astrobiology and remote robotic planetary exploration. It can be used to identify and characterise rock matrices, mineral inclusions and organic molecules and is demonstrably effective at identifying biomarkers, or indicators of biological activity. The ExoMars rover, jointly operated by the European and Russian Federal Space Agencies, will carry the first Raman spectrometer into space when it launches in 2018 and two further Raman instruments have recently been announced as part of the payload onboard the National Aeronautics and Space Administration's Mars 2020 rover. Each of these spectrometers however will, by necessity, have poorer resolution than the most sophisticated laboratory instruments because of mass, volume and power constraints and the space readiness of the requisite technologies. As a result, it is important to understand the minimum instrument specification required to achieve the scientific objectives of a mission, in terms of parameters such as spectral resolution and laser footprint size. This requires knowledge of the target minerals and molecules between which there may be ambiguity when identifying bands in spectra from geological samples. Here, we present spectra from a number of Mars analogue samples that include a range of such molecules, highlighting where such confusion may occur and identifying the most useful bands for differentiation. It is recommended that a Raman spectrometer achieves a resolution of at least 3 cm−1 and covers a spectral range from 100 to 4000 cm−1 in order to differentiate between all of the target molecules presented here. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]