Geochemical characterization of the Martian analogues Enekuri and Fruiz, located in the Basque-Cantabrian Basin, by spectroscopic techniques.

This work presents the geochemical characterization of two Martian analogues located in the Basque-Cantabrian Basin: Enekuri and Fruiz. In contrast to previous works carried out on the coastline analogues Meñakoz and Armintza (Biscay, Spain), these new outcrops are not in contact with sea-water nowadays. Hence, the weathering processes observed in Enekuri and Fruiz (inland) are different from those observed in Armintza and Meñakoz (coastline). In this way, among all the mineral phases found the only ones in common between inland and coastline outcrops are albite and chlorites, minerals that were formed in aqueous conditions. Understanding the differences presented in both types of outcrops could help to interpret the future results from the missions Mars2020 and the ExoMars2022, since coastline outcrops are affected by sea-water weathering and inland outcrops are altered by the high biological activity.

Interrelationships in the Gypsum-Syngenite-Görgeyite System and Their Possible Formation on Mars.

Calcium sulfates are known to be potential reservoirs of organic compounds and have been detected on Mars. However, not all data that indicate the presence of sulfates collected by the Mars Exploration Rovers (Spirit and Opportunity) and Curiosity rover can be explained by the different calcium sulfate polymorphs, and therefore, mixtures of calcium sulfates with other single sulfates must be considered. In addition, the presence of mixed calcium sulfates supports the data and indicates that the molar ratio of sulfate/calcium is >1. To obtain adequate spectroscopic information of mixed-cation sulfates to be used in the interpretation of data from Mars in the next few years, the thermodynamically stable syngenite (K2Ca(SO4)2·H2O) and görgeyite (K2Ca5(SO4)6·H2O) mixed-cation sulfates have been studied along with the interrelationships in the gypsum-syngenite-görgeyite system to understand their possible formation on Mars. Raman spectroscopy and Visible-Near Infrared-Shortwave Infrared (VisNIR) spectroscopy have been used for their characterization to increase the databases for the two future Mars exploration missions, Mars2020 and ExoMars2022, where both techniques will be implemented. These VisNIR data can also help with the interpretation of spectral data of salt deposits on Mars acquired by the OMEGA and CRISM spectrometers onboard the Mars Express and Mars Reconnaissance orbiters. This work demonstrates that syngenite (K2Ca(SO4)2·H2O) easily precipitates without the need for hydrothermal conditions, which, depending on the ion concentrations, may precipitate in different proportions with gypsum. Furthermore, in this study, we also demonstrate that, under hydrothermal conditions, görgeyite (K2Ca5(SO4)6·H2O) would also be highly likely to form and may also be identified on Mars together with syngenite and gypsum.

ExoMars Raman Laser Spectrometer: A Tool for the Potential Recognition of Wet-Target Craters on Mars.

In the present work, near-infrared, laser-induced breakdown spectroscopy, Raman, and X-ray diffractometer techniques have been complementarily used to carry out a comprehensive characterization of a terrestrial analogue selected from the Chesapeake Bay impact structure (CBIS). The obtained data clearly highlight the key role of Raman spectroscopy in the detection of minor and trace compounds, through which inferences about geological processes occurred in the CBIS can be extrapolated. Beside the use of commercial systems, further Raman analyses were performed by the Raman laser spectrometer (RLS) ExoMars Simulator. This instrument represents the most reliable tool to effectively predict the scientific capabilities of the ExoMars/Raman system that will be deployed on Mars in 2021. By emulating the analytical procedures and operational restrictions established by the ExoMars mission rover design, it was proved that the RLS ExoMars Simulator can detect the amorphization of quartz, which constitutes an analytical clue of the impact origin of craters. Beside amorphized minerals, the detection of barite and siderite, compounds crystallizing under hydrothermal conditions, helps indirectly to confirm the presence of water in impact targets. Furthermore, the RLS ExoMars Simulator capability of performing smart molecular mappings was successfully evaluated.