18th EANA Conference European Astrobiology Network Association Abstract book 24-28 September 2018 Freie Universität Berlin, Germany Sponsors: Detectability of biosignatures in martian sedimentary systems A. H. Stevens1, A. McDonald2, and C. S. Cockell1 (1) UK Centre for Astrobiology, University of Edinburgh, UK ([email protected]) (2) Bioimaging Facility, School of Engineering, University of Edinburgh, UK Presentation: Tuesday 12:45-13:00 Session: Traces of life, biosignatures, life detection Abstract: Some of the most promising potential sampling sites for astrobiology are the numerous sedimentary areas on Mars such as those explored by MSL. As sedimentary systems have a high relative likelihood to have been habitable in the past and are known on Earth to preserve biosignatures well, the remains of martian sedimentary systems are an attractive target for exploration, for example by sample return caching rovers [1]. To learn how best to look for evidence of life in these environments, we must carefully understand their context. While recent measurements have raised the upper limit for organic carbon measured in martian sediments [2], our exploration to date shows no evidence for a terrestrial-like biosphere on Mars. We used an analogue of a martian mudstone (Y-Mars[3]) to investigate how best to look for biosignatures in martian sedimentary environments. The mudstone was inoculated with a relevant microbial community and cultured over several months under martian conditions to select for the most Mars-relevant microbes. We sequenced the microbial community over a number of transfers to try and understand what types microbes might be expected to exist in these environments and assess whether they might leave behind any specific biosignatures. We also pre-pared abiotic controls and samples with a single known species (Bacillus subtilis) under the same conditions to as-sess detection limits for the techniques under investigation. The dominant microbes in our incubations were similar to early colonisers, including a wide array of Proteobacteria, especially Alpha- and Gammaproteobacteria and including purple sulfur bacteria. Other notable genera that dominated the developing microbial communities were Chlorobiaceae, Geobacter and Oxalobactereaceae. Methanogenic archaea were also highly abundance in some transfers. We pressed the inoculated analogue material into pellets to simulate mudstone formation and then used a variety of biosignature detection techniques to test what was observable in our samples. Since the ExoMars rover will carry a Raman spectrometer, and the Mars 2020 rover another two, we used a Raman instrument to generate maps of the samples. The pellets were also analysed by GCMS, and LIMS as analogues of other rover instruments. No biological signatures were apparent in bulk GCMS analysis, in either carbon, nitrogen or sulfur abundance, or isotopic fractionation of carbon or sulfur. Raman and LIMS analysis showed some spatially distinct biological sig-natures, but these were not definitive and subject to interference from some of the minerals in the analogue mudrock. These results suggest a number of problems relating to biosignature detection in the context of martian sedimentary systems that should be taken into account for future missions. Developing strategies to avoid these problems will reduce the likelihood of false positives or negatives. References: [1] Hays, L.E., et al., Astrobiology, 2017. 17(4): p. 363-400. [2] Eigenbrode, J.L., et al., Science, 2018. 360(6393): p. 1096-1101. [3] Stevens, A.H., et al., Earth and Space Science, 2018. 5: p. 163-174. From quantum computational physics to the origins of life A. Marco Saitta and Fabio Pietrucci Sorbonne Université, Institut de Minéralogie, de Physique des Matériaux et de Cosmochimie, CNRS, MNHN, Paris France Presentation: Wednesday 15:15-15:30 Session: The building blocks of life Abstract: Computational approaches are nowadays a full, self-standing branch of chemistry, both for their quan-tum- based ("ab initio") accuracy, and for its multiscale extent. In prebiotic chemistry, however, due to the instrinsic complexity of the chemical problems, ab initio atomistic simulations have so far had a lim-ited impact, with the exception of a few relevant studies, including the elucidation of the chemical inter-actions between biomolecules with surfaces, such as ice and minerals, or the simulation of the effect of the pressure/temperature shock waves induced by meteorite impacts in the early Earth. Surprisingly, even the celebrated Miller experiments, which historically reported on the spontaneous formation of amino-acids from a mixture of simple molecules reacting under an electric discharge, have never been studied at the quantum atomistic level. Here we set the general problem of chemical networks within new topology-based concepts, using search algorithms and social network data analysis. This allows a very efficient definition of reaction coordinates even in the complex chemical environments which are typical of likely prebiotic scenarii. We thus report on the first ab initio computer simulations, based on quantum physics and a fully atomistic approach, of Miller- like experiments in the condensed phase. Our study [1] shows that glycine spontane-ously form from mixtures of simple molecules once an electric field is switched on. We identify formic acid and formamide [2] as key intermediate products of the early steps of the Miller reactions, and the crucible of formation of complex biological molecules, as confirmed by our recent experimental and theoretical study on high- energy chemistry of formamide [3]. From a broader chemical perspective, we show that formamide plays the role of hub of a complex reaction network in both the gas and the con-densed phase [4]. We are now going on a larger scale, studying the atomistic mechanisms of RNA nucle-otides synthesis [5], meteoritic amino acids [6] and sugars [7] in fully realistic prebiotic solution envi-ronments. All these results pave the way to novel computational approaches in the research of the chemi-cal origins of life. Figure 1: Left, pictorial representation of the reaction paths connecting A and B, with possible C or D intermediates. Right, example of a fully quantum atomistic simulation of the A-to-B degradation/synthesis reaction between one uridine mono-phosphate nucleotide and one uracil plus a phosphoribose, in explicit water solution. References: [1] Saitta AM and Saija F (2014) Proceedings of the National Academy of Sciences USA 111:13768-13773. [2] Saitta AM, Saija F, Pietrucci F, and Guyot F (2015) Proceedings of the National Academy of Sciences USA 112, E343-E343. [3] Ferus M et al. (2017) Proceedings of the National Academy of Sciences USA, 114:4306-4311. [4] Pietrucci F and Saitta AM (2015) Proceedings of the National Academy of Sciences USA 112, 15030-15035. [5] Perez-Villa A et al. (2017) submitted. [6] Pietrucci F et al. (2018) ACS Earth Space Chem, to appear. [7] Cassone G et al. (2018) Chem Comm 54, 3211. Are the Adaptations Used by Microorganisms at the Limits of Life "One-Size-Fits- All" or "Bespoke"? Adrienne Kish Muséum National d'Histoire Naturelle, France Presentation: Poster Session: Evolution of life and its environment Abstract: Planetary conditions, whether we consider Mars or the icy moons of Jupiter, are considered "extreme" by modern terrestrial standards, and thus hostile to life. Even conditions on the early are considered as extreme. We therefore often turn to modern extremophile microorganisms to explore the limits of life and to determine what molecular-level adaptations can be used by living cells to counteract the deleterious effects of extremes in temperatures, pH, irradiation levels, concentrations of salts and metals, and desiccation. When studying these organisms in the lab, there is a however tenancy to examine microbial adaptations to a single stress condition. While it represents good scientific methodology to examine one variable at a time, the results of these sorts of studies tend to be presented as "bespoke" adaptations of microorganisms to a single stress factor. The natural habitats of extremophile microorganisms, however, are most often a mix of multiple "extreme" conditions. High temperature waters often have a strong pH bias (acidic or alkaline), water at low temperatures requires elevated salt concentrations to remain liquid, and deep sea hydrothermal vents are a mix of temperature stresses, pH extremes, high concentrations of metals, and high hydrostatic pressures. This mix of stresses holds true for other planetary bodies as well, for both past and present conditions. Examination of the survival of modern microorganisms under multi-stress conditions reveals a subset of molecular adaptations used by cells can also be multi-purpose. Evolutionarily acquired adaptations to one stress may as a consequence increase resistance to other stresses, while other adaptions are part of a general stress response. In this context, adaptations to this mix of stresses can be regarded as less "bespoke" and more "off-the-rack". Taken even further, studies have shown that the adaptations of some terrestrial extremophiles enable their survival against conditions that never occur in their natural habitats (ionizing radiation, for example)1,2. Some adaptations, such as proteinaceous surface layers (S-layers) aid resistance against most stress conditions (extremes in temperature, osmotic pressure, high concentrations of metals, etc)3,4, and can even play a role in the