The Raman Laser Spectrometer (RLS) on board the ESA/Roscosmos ExoMars 2020 mission will provide precise identification of the mineral phases and the possibility to detect organics on the Red Planet. The RLS will work on the powdered samples prepared inside the Pasteur analytical suite and collected on the surface and subsurface by a drill system. Raman spectroscopy is a well-known analytical technique based on the inelastic scattering by matter of incident monochromatic light (the Raman effect) that has many applications in laboratory and industry, yet to be used in space applications. Raman spectrometers will be included in two Mars rovers scheduled to be launched in 2020. The Raman instrument for ExoMars 2020 consists of three main units:(1) a transmission spectrograph coupled to a CCD detector; (2) an electronics box, including the excitation laser that controls the instrument functions; and (3) an optical head with an autofocus mechanism illuminating and collecting the scattered light from the spot under investigation. The optical head is connected to the excitation laser and the spectrometer by optical fibers. The instrument also has two targets positioned inside the rover analytical laboratory for onboard Raman spectral calibration. The aim of this article was to present a detailed description of the RLS instrument, including its operation on Mars. To verify RLS operation before launch and to prepare science scenarios for the mission, a simulator of the sample analysis chain has been developed by the team. The results obtained are also discussed. Finally, the potential of the Raman instrument for use in field conditions is addressed. By using a ruggedized prototype, also developed by our team, a wide range of terrestrial analog sites across the world have been studied. These investigations allowed preparing a large collection of real, in situ spectra of samples from different geological processes and periods of Earth evolution. On this basis, we are working to develop models for interpreting analog processes on Mars during the mission.

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A comprehensive micro-Raman spectroscopic analysis of the Nakhla and Vaca Muerta meteorites is reported. The major and minor mineral components were identified from comparison with mineralogical standards and literature databases. The compositions of pyroxenes and olivines were obtained using only this technique and correlation data between band parameters and the chemical composition of reference materials existing in the literature. The presence of calcite in both meteorite specimens was noted; its identification inside eucrite grains in the Vaca Muerta meteorite is particularly noteworthy. Their spectral parameters show strong similarities. Aragonite associated with calcite is reported for the first time in Vaca Muerta meteorite. Spectra of siderite, which appears associated with clinopyroxenes, are also reported in Nakhla meteorite. Iron oxides were analysed in detail in both meteorites. Magnetite is the main oxide phase observed in Nakhla and goethite, lepidocrocite and magnetite in Vaca Muerta. In both cases haematite was not observed. A comparison of the spectral parameters of these mineral phases observed in both meteorites was made and their possible origin as secondary minerals is discussed. This study stresses the potential of Raman spectroscopy in the mineralogical characterization of meteorites on a very small scale and also the potential applications of Raman spectroscopy for use on landers or rovers on the surface of Mars or other planetary bodies.

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