RESUMEN

In this work, a geological sample of great astrobiological interest was studied through analytical techniques that are currently operating in situ on Mars and others that will operate in the near future. The sample analyzed consisted of an oncoid, which is a type of microbialite, collected in the Salar Carachi Pampa, Argentina. The main peculiarity of microbialites is that they are organo-sedimentary deposits formed by the in situ fixation and precipitation of calcium carbonate due to the growth and metabolic activities of microorganisms. For this reason, the Carachi Pampa oncoid was selected as a Martian analog for astrobiogeochemistry study. In this sense, the sample was characterized by means of the PIXL-like, SuperCam-like and SHERLOC-like instruments, which represent instruments on board the NASA Perseverance rover, and by means of RLS-like and MOMA-like instruments, which represent instruments on board the future ESA Rosalind Franklin rover. It was possible to verify that the most important conclusions and discoveries have been obtained from the combination of the results. Likewise, it was also shown that Perseverance rover-like remote-sensing instruments allowed a first detailed characterization of the biogeochemistry of the Martian surface. With this first characterization, areas of interest for in-depth analysis with Rosalind Franklin-like instruments could be identified. Therefore, from a first remote-sensing elemental identification (PIXL-like instrument), followed by a remote-sensing molecular characterization (SuperCam and SHERLOC-like instruments) and ending with an in-depth microscopic analysis (RLS and MOMA-like instruments), a wide variety of compounds were found. On the one hand, the expected minerals were carbonates, such as aragonite, calcite and high-magnesium calcite. On the other hand, unexpected compounds consisted of minerals related to the Martian/terrestrial surface (feldspars, pyroxenes, hematite) and organic compounds related to the past biological activity related to the oncoid (kerogen, lipid biomarkers and carotenes). Considering samples resembling microbialites have already been found on Mars and that one of the main objectives of the missions is to identify traces of past life, the study of microbialites is a potential way to find biosignatures protected from the inhospitable Martian environment. In addition, it should be noted that in this work, further conclusions have been obtained through the study of the results as a whole, which could also be carried out on Mars.

RESUMEN

The SuperCam instrument, onboard the Perseverance rover (Mars 2020 mission) is designed to perform remote analysis on the Martian surface employing several spectroscopic techniques such as Laser Induced Breakdown Spectroscopy (LIBS), Time-Resolved Raman (TRR), Time-Resolved Fluorescence (TRF) and Visible and Infrared (VISIR) reflectance. In addition, SuperCam also acquires high-resolution images using a color remote micro-imager (RMI) as well as sounds with its microphone. SuperCam has three main subsystems, the Mast Unit (MU) where the laser for chemical analysis and collection optics are housed, the Body Unit (BU) where the different spectrometers are located inside the rover, and the SuperCam Calibration Target (SCCT) located on the rover's deck to facilitate calibration tests at similar ambient conditions as the analyzed samples. To perform adequate calibrations on Mars, the 22 mineral samples included in the complex SCCT assembly must have a very homogeneous distribution of major and minor elements. The analysis and verification of such homogeneity for the 5-6 replicates of the samples included in the SCCT has been the aim of this work. To verify the physic-chemical homogeneity of the calibration targets, micro Energy Dispersive X-ray Fluorescence (EDXRF) imaging was first used on the whole surface of the targets, then the relative abundances of the detected elements were computed on 20 randomly distributed areas of 100 × 100 µm. For those targets showing a positive Raman response, micro-Raman spectroscopy imaging was performed on the whole surface of the targets at a resolution of 100 × 100 µm. The %RSD values (percent of relative standard deviation of mean values) for the major elements measured with EDXRF were compared with similar values obtained by two independent LIBS set-ups at spot sizes of 300 µm in diameter. The statistical analysis showed which elements were homogeneously distributed in the 22 mineral targets of the SCCT, providing their uncertainty values for further calibration. Moreover, nine of the 22 targets showed a good Raman response and their mineral distributions were also studied. Those targets can be also used for calibration purposes of the Raman part of SuperCam using the wavenumbers of their main Raman bands proposed in this work.

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RESUMEN

The landing site of the next planetary mission lead by ESA (ExoMars 2022) will be Oxia Planum. This location has been chosen due to different reasons, among them, the existence of sedimentary rocks that could host remains of organic matter. The fact that this type of rocks coexists with volcanic ones makes of high importance the study of the processes and the possible interactions that could happen among them. Therefore, in this research work the Armintza outcrop (Biscay, North of Spain) is proposed as an Oxia Planum analogue since it has the dichotomy of volcanic and sedimentary rock layers that is expected on the landing site of the ExoMars 2022 mission. As Raman and visible near infrared spectroscopies will be in the payload of the rover of that mission, they have been used to characterize the samples collected in the Armintza outcrop. With the help of these techniques, feldspars (albite mainly) and phyllosilicates (kaolinite and dickite, together with micas and chlorite minerals) have been identified as the major products on the samples, together with some weathering products (carbonates, sulphates, oxides) and apatite. Moreover, remains of kerogen have been detected in the sedimentary layers in contact with the interlayered lava flows, confirming the capability of similar sedimentary-volcanic layers to trap and store organic remains for millions of years. After establishing which compounds have volcanic or sedimentary origin, and which must be considered alteration phases, we can consider Armintza as a good Oxia Planum analogue.

RESUMEN

This work proposes an innovative non-destructive analytical strategy, based on Confocal Raman micro-spectroscopy, High Resolution Raman Imaging and micro-X-Ray Fluorescence imaging, as part of the quick non-destructive techniques that could be used to characterize the Martian samples from the Mars Sample Return mission when back on Earth. Until that moment, Martian Meteorites are the only Martian samples in our hands to develop such Analytical Strategies. To demonstrate its capabilities, this analytical strategy has been applied to characterize the Dar al Gani 735 Martian Meteorite with the aim to identify the terrestrial and non-terrestrial alterations suffered by the meteorite as a very valuable complementary methodology to the more traditional petrographic analyses and single point measurements. The combination of these techniques allows extracting at the same time elemental, molecular and structural information of the studied area of the sample. The most relevant results on the analyzed DaG 735 shergottite thick samples revealed the presence of several altered mineral phases originated from the temperature and pressure conditions during the shock on Mars (anhydride, calcite and ilmenite), as well as from terrestrial weathering processes that degraded the meteorite from its landing on Earth (calcite and hematite in fractures together with gypsum, mirabilite and thenardite). As most of the conclusive results come from Raman spectroscopy, this study shows the potential of Raman spectroscopy as a key technique in the upcoming new explorations of Mars materials by the Rosalind Franklin rover (Exomars2022 mission from ESA) and the Perseverance rover (Mars2020 mission from NASA), where Raman spectrometers are mounted for the first time in an extra-terrestrial research in the field.