Development of non-destructive analytical strategies based on Raman spectroscopy and complementary techniques for Mars Sample Return tested on Northwest Africa 1950 Martian meteorite

The Mars Sample Return (MSR) is a near future mission to return samples from the surface of Mars to the Earth. The field operations to carry out data collection, selection of the samples, and sampling procedure, mainly related to the CanMars MSR analog mission, are well-studied and published. In contrast, studies related to the methodology implemented to characterize the mineralogy of the returned samples are scarcer and focused on biosignature detection. This work presents a non-destructive analytical methodology based on Raman microscopy (single point and imaging), micro-energy dispersive X-ray fluorescence imaging analysis, and scanning electron microscopy coupled to energy dispersive spectroscopy that could be used as a first analytical characterization for the Martian samples that will be returned to the Earth in the upcoming MSR mission, before any destructive analysis. The analytical methodology has been tested on a fragment of the Northwest Africa 1950 Martian meteorite, which gives us a mineralogical characterization of the meteorite. This methodology also allowed to define several chemical reactions taking place in some of the mineral phases (olivines and ilmenite) of the meteorite. In addition to the geochemical characterization of the samples, the fact that this methodology allows to assess the chemical transformations in several minerals gives important clues for describing mineral processes and geological evolution that took place on Mars. This work also shows the advantages and disadvantages that each of the techniques employed has when performing a mineralogical characterization, the information that each one can provide and the importance of combining them. This work has been financially supported through the RamOnMars project: “Contribution of the Raman spectroscopy to the exploration of Mars and Martian Moons: ExoMars, Mars 2020, and MMX missions” (Grant ESP2017-87690-C3-1-R), funded by the Spanish Ministry of Science and Innovation (MICINN) and the European Regional Development Fund (FEDER) and by the Spanish Agency for Research (AEI-MINECO/FEDER) through the Project Science and Instrumentation for the Study of (bio)geochemical processes in Mars (Sigue-Mars), Grant no. RED2018-102600-T. C. García-Florentino is grateful to the Basque Government for her Postdoctoral Grant. J. Huidobro is grateful to the Basque Government for her Predoctoral contract. I. Torre-Fdez acknowledges his predoctoral contract from the University of the Basque Country (UPV/EHU). J. Aramendia is grateful to the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 754513 and The Aarhus University Research Foundation for her fellowship. The authors thank the General Service of Electron Microscopy and Materials Microanalysis Laboratory from the SGIker (UPV/EHU, MICINN, GV/EJ, ERDF and ESF) of the University of the Basque Country for their collaboration in the analyses.