Spectroscopic Studies of Molecular Systems Relevant in Astrobiology

In the Astrobiology context, the study of the physico-chemical interactions involving \u201cbuilding blocks of life\u201d in plausible prebiotic and space-like conditions is fundamental to shed light on the processes that led to emergence of life on Earth as well as to molecular chemical evolution in space. In this PhD Thesis, such issues have been addressed both experimentally and computationally by employing vibrational spectroscopy, which has shown to be an e\ufb00ective tool to investigate the variety of intermolecular interactions that play a key role in self-assembling mechanisms of nucleic acid components and their binding to mineral surfaces. In particular, in order to dissect the contributions of the di\ufb00erent interactions to the overall spectroscopic signals and shed light on the intricate experimental data, feasible computational protocols have been developed for the characterization of the spectroscopic properties of such complex systems. This study has been carried out through a multi-step strategy, starting the investigation from the spectroscopic properties of the isolated nucleobases, then studying the perturbation induced by the interaction with another molecule (molecular dimers), towards condensed phases like the molecular solid, up to the case of nucleic acid components adsorbed on minerals

Prominent autistic traits and subthreshold bipolar/mixed features of depression in severe anorexia nervosa

Autistic traits are associated with a burdensome clinical presentation of anorexia nervosa (AN), as is AN with concurrent depression. The aim of the present study was to explore the intertwined association between complex psychopathology combining autistic traits, subthreshold bipolarity, and mixed depression among people with AN

Life detection in Martian returned samples: correlation between analytical techniques and biological signatures

As soon as samples collected from Mars will be brought back to Earth, the samples will be placed inside a receiving facility to check for the presence of life. There is a large number of approaches that were proposed on the techniques to be used to investigate the presence of life and any biological risk in the returned samples. Another interesting approach was reported by Kminek in which suggestions were provided on how to organize the sample analysis sequence within the facility. Finally, another study suggested a long list of techniques capable of measuring biological signatures based on their general characteristics: global, morphological, mineralogical, organic, molecular and biochemical, isotopic analysis. Despite the effort of the cited studies, there is still the need of a critical approach to make an actual comparison between the techniques, with the aim to find a ranking. In this work, we focused on the construction of a correlation matrix with which to correlate biosignatures to analytical techniques. It is known that a number of techniques can detect biological signatures and, at the same time, each technique can be applied to multiple biological signatures. Using this method, it is possible to summarize all this information to be easily consulted, but also to define in a quantitative way how strong each correlation is

Analysis of organic compounds in Mars soil analog samples using SuperCam-Raman of Mars2020

One of the main objectives of the Perseverance rover is to find signs of ancient life in the Martian surface, seeking biosignatures and signs of past habitable conditions. This could be achieved with the finding of organic compounds related to life. Raman spectroscopy is among the techniques that the rover is capable of performing, which is able to detect and discern organic molecules. Perseverance carries in its payload two instruments that are able to use this technique, SuperCam for remote sensing and SHERLOC for proximity measurements. SuperCam is a long-distance instrument capable of performing several techniques (Raman, LIBS, luminescence, VISIR, microphone) in order to assess the chemical and molecular composition of rocks (mineral phases and organic molecules) from a distance up to 7 m. Therefore, it could detect organics, or traces of them, from a distance before the rover gets closer.In this work, a set of Mars soil analog samples were analyzed using the Flying Model-Body Unit / Engineering Qualification Model-Mast Unit (FM-BU/EQM-MU) setup of SuperCam. Specifically, the samples were prepared in the laboratory by adsorbing adenosine 5"-monophosphate, L-glutamic acid, L-phenylalanine, and phthalic acid with different known concentrations (5 wt%, 1 wt% and 0.1 wt%) on the clay mineral montmorillonite doped with 1 wt% of Mg-perchlorate. The preparation and characterization of those samples can be found in literature [1]. The analyses were carried out at a 2 m distance from the targets, with a laser spot size of around 300 µm at that distance. SuperCam showed excellent results for the pure compounds, before adsorption on the clay mineral. At 5 wt% concentration, the Raman signals of the organics were barely visible and at 1 wt% they were no longer visible. This fact means that if the laser of SuperCam hits an organic "hotspot" in a rock from a distance, it will be able to detect it as long as it has a concentration around 5 wt% or greater in the analyzed area, allowing SHERLOC to do further contact analysis afterwards. In addition, the SuperCam results were compared with those obtained with a commercial laboratory instrument (Renishaw inVia), obtaining the same main signals and only missing some minor secondary bands.[1] T. Fornaro, J. R. Brucato, G. Poggiali, M. A. Corazzi, M. Biczysko, M. Jaber, D. I. Foustoukos, R. M. Hazen, A. Steele, UV irradiation and Near Infrared characterization of laboratory Mars soil analog samples, Frontiers in Astronomy and Space Sciences, 2020, 7, 1-2

Ultraviolet Photoprocessing of Glycine Adsorbed on Various Space-Relevant Minerals

The discovery of amino acids such as glycine on meteorites and comets confirms the role of small bodies as transport and delivery vehicles of building blocks of life on Earth and possibly on other planetary bodies of our Solar System. Glycine is quite interesting because it is the simplest of the 20 biogenic amino acids, from which complex organic molecules might have originated in our evolved Solar System. To investigate the possible chemical evolution of this molecule in space, it is important to consider how the interaction with mineral matrices influences its photostability. Indeed, the presence of minerals can mediate the effects of electromagnetic radiation, catalyzing photoreactions, or protecting molecules against degradation. Such interactions are responsible for the preservation/degradation mechanisms of organic molecules in space environments. Laboratory simulations of UV processing may provide key insights into the survival of organic molecules in space environment and rocky surfaces, which is of particular relevance for current missions of sample return from asteroids, such as NASA OSIRIS-REx and JAXA Hayabusa 2, and in particular, upcoming space exploration missions on planetary surfaces, such as ESA-Roscosmos ExoMars 2022 and NASA Mars 2020. In this article, we report a laboratory study of UV irradiation of glycine adsorbed on various space relevant minerals: forsterite, antigorite, spinel, and pyrite. We monitored possible changes of glycine functional groups due to UV irradiation through in situ infrared (IR) spectroscopic analysis. Results show that degradation of glycine occurs with a half-life of 0.5–2 h depending on the mineral substrate. Appearance of new IR bands suggests the occurrence of catalytic reactions mediated by minerals and UV

Detection and Degradation of Adenosine Monophosphate in Perchlorate-Spiked Martian Regolith Analogue, by Deep-Ultraviolet Spectroscopy

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

Toward the design of alkynylimidazole fluorophores: computational and experimental characterization of spectroscopic features in solution and in poly(methyl methacrylate)

The possibilities offered by organic fluorophores in the preparation of advanced plastic materials have been increased by designing novel alkynylimidazole dyes, featuring different push and pull groups. This new family of fluorescent dyes was synthesized by means of a one-pot sequential bromination–alkynylation of the heteroaromatic core, and their optical properties were investigated in tetrahydrofuran and in poly(methyl methacrylate). An efficient in silico pre-screening scheme was devised as consisting of a step-by-step procedure employing computational methodologies by simulation of electronic spectra within simple vertical energy and more sophisticated vibronic approaches. Such an approach was also extended to efficiently simulate one-photon absorption and emission spectra of the dyes in the polymer environment for their potential application in luminescent solar concentrators. Besides the specific applications of this novel material, the integration of computational and experimental techniques reported here provides an efficient protocol that can be applied to make a selection among similar dye candidates, which constitute the essential responsive part of those fluorescent plastic materials

The photochemical evolution of polycyclic aromatic hydrocarbons and nontronite clay on early Earth and Mars

The photochemical evolution of polycyclic aromatic hydrocarbons (PAHs), an abundant form of meteoritic organic carbon, is of great interest to early Earth and Mars origin-of-life studies and current organic molecule detection efforts on Mars. Fe-rich clay environments were abundant on early Earth and Mars, and may have played a role in prebiotic chemistry, catalyzing the breakdown of PAHs and freeing up carbon for subsequent chemical complexification. Current Mars is abundant in clay-rich environments, which are most promising for harboring organic molecules and have comprised the main studied features by the Curiosity rover in search of them. In this work we studied the photocatalytic effects of the Fe-rich clay nontronite on adsorbed PAHs. We tested the effect of ultraviolet radiation on pyrene, fluoranthene, perylene, triphenylene, and coronene adsorbed to nontronite using the spike technique, and in situ diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy in a Mars simulation chamber. We studied the infrared vibrational PAH bands with first order reaction kinetics and observed an extensive decrease of bands of pyrene, fluoranthene, and perylene, accompanied by the formation of PAH cations, while triphenylene and coronene remained preserved. We further analyzed our irradiated samples with nuclear magnetic resonance (NMR). Our study showed certain PAHs to be degraded via the (photo)Fenton mechanism, even under a dry, hypoxic atmosphere. Using solar spectra representative of early Earth, early Mars, and current Mars surface illumination up to 400 nm, the processes occurring in our set up are indicative of the UV-induced photochemistry taking place in Fe-rich clay environments on early Earth and Mars

Constraining the preservation of organic compounds in Mars analog nontronites after exposure to acid and alkaline fluids

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 conditionsEuropean Commission | Ref. FP7 n. 307496European Commission | Ref. H2020 n. 818602Ministerio de Economía | Ref. MDM-2017-0737Ministerio de Economía | Ref. ESP2017-89053-C2-1-