Examinando por Autor "Fornaro, T."

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Acceso Abierto
Constraining the preservation of organic compounds in Mars analog nontronites after exposure to acid and alkaline fluids.
(Nature Research Journals, 2020-09-15) Gil Lozano, C.; Fairén, Alberto G.; Muñoz Iglesias, V.; Fernández Sampedro, M.; Prieto Ballesteros, O.; Gago Duport, L.; Losa Adams, E.; Carrizo, D.; Bishop, J. L.; Fornaro, T.; Mateo Martí, Eva; European Research Council (ERC); Agencia Estatal de Investigación (AEI); European Commission (EC); 0000-0002-5536-2565; 0000-0003-1932-7591; 0000-0002-1159-9093; 0000-0003-3500-2850; 0000-0002-2278-1210; 0000-0002-2646-5995; Unidad de Excelencia Científica María de Maeztu Centro de Astrobiología del Instituto Nacional de Técnica Aeroespacial y CSIC, MDM-2017-0737
The presence of organic matter in lacustrine mudstone sediments at Gale crater was revealed by the Mars Science Laboratory Curiosity rover, which also identified smectite clay minerals. Analogue experiments on phyllosilicates formed under low temperature aqueous conditons have illustrated that these are excellent reservoirs to host organic compounds against the harsh surface conditions of Mars. Here, we evaluate whether the capacity of smectites to preserve organic compounds can be influenced by a short exposure to different diagenetic fluids. We analyzed the stability of glycine embedded within nontronite samples previously exposed to either acidic or alkaline fluids (hereafter referred to as "treated nontronites") under Mars-like surface conditions. Analyses performed using multiple techniques showed higher photodegradation of glycine in the acid-treated nontronite, triggered by decarboxylation and deamination processes. In constrast, our experiments showed that glycine molecules were preferably incorporated by ion exchange in the interlayer region of the alkali-treated nontronite, conferring them a better protection against the external conditions. Our results demonstrate that smectite previously exposed to fluids with different pH values influences how glycine is adsorbed into their interlayer regions, affecting their potential for preservation of organic compounds under contemporary Mars surface conditions.
Restringido
Detection and Degradation of Adenosine Monophosphate in Perchlorate-Spiked Martian Regolith Analog, by Deep-Ultraviolet Spectroscopy
(Mary Ann Liebert Publishers, 2021-01-25) Razzell Hollis, J.; Fornaro, T.; Rapin, W.; Wade, J.; Vicente Retortillo, Á.; Steele, A.; Bhartia, R.; Beegle, W.; Agenzia Spaziale Italiana (ASI)
The search for organic biosignatures on Mars will depend on finding material protected from the destructive ambient radiation. Solar ultraviolet can induce photochemical degradation of organic compounds, but certain clays have been shown to preserve organic material. We examine how the SHERLOC instrument on the upcoming Mars 2020 mission will use deep-ultraviolet (UV) (248.6 nm) Raman and fluorescence spectroscopy to detect a plausible biosignature of adenosine 5′-monophosphate (AMP) adsorbed onto Ca-montmorillonite clay. We found that the spectral signature of AMP is not altered by adsorption in the clay matrix but does change with prolonged exposure to the UV laser over dosages equivalent to 0.2–6 sols of ambient martian UV. For pure AMP, UV exposure leads to breaking of the aromatic adenine unit, but in the presence of clay the degradation is limited to minor alteration with new Raman peaks and increased fluorescence consistent with formation of 2-hydroxyadenosine, while 1 wt % Mg perchlorate increases the rate of degradation. Our results confirm that clays are effective preservers of organic material and should be considered high-value targets, but that pristine biosignatures may be altered within 1 sol of martian UV exposure, with implications for Mars 2020 science operations and sample caching.