The crucial role of molecular emissions on LIBS differentiation of organic compounds of interest in astrobiology under a Mars simulated atmosphere

In this work, the influence of Martian atmosphere on the recombination mechanisms in laser-induced plasmas of organic compounds of interest in astrobiology has been closely examined. The proposed LIBS methodology reveals new insights concerning the influence of the surrounding atmosphere on the molecular emission of organics. The presence of nitrogen, even in the short concentration found in the low-pressure Mars environment, influences the plasma chemistry and the formation pathways leading to molecular species. Characteristic atomic and molecular emitters (C, H, C2, CN, NH, OH and CH) were inspected in a set of selected organic compounds considered as meaningful biomarkers. For comparative purposes, LIBS analysis was performed in both low-pressure air and Martian atmospheres. Statistical analysis (linear discriminant analysis; DFA) suggested that satisfactory differentiation among materials was feasible under Martian conditions when molecular emissions are computed in the classification algorithm. Atomic lines (C, H) only contribute a mere ~62% to the discriminating analysis, whereas the percentage of successful discrimination was considerably increased (up to 99%) by the progressive introduction of signals associated to molecular bands into the DFA analysis, thus confirming the major contribution of molecular information to the final sorting performance and the feasibility of discriminating closely related organic compounds by LIBS in the Martian atmosphere.his work was partially supported by Programa Operativo FEDER Andalucía 2014–2020, Consejería de Economía y Conocimiento de la Junta de Andalucía, Reference UMA18-FEDERJA-272 and by Project PID2020-119185GB-I00 from Ministerio de Ciencia e Innovación, Spain. The authors would also like to acknowledge the support of the SIGUE-Mars Research Network, the International Space Science Institute (ISSI) Bern and the International Space Science Institute (ISSI) Beijing. // Funding for open access charge: Universidad de Málaga / CBU

Detection of kerogens in sedimentary rocks by LIBS. Implications for the search for biosignatures on Mars.

Congreso Internacional dedicado a la aplicaciones de LIBSOil shale is a sedimentary rock that naturally contains organic matter. In its chemical composition presents a wide range of inorganic minerals including carbonates, silicates, etc. and kerogens – a mixture of fossil hydrocarbons. Kerogen is insoluble in normal organic solvents, being the most abundant source of organic matter on Earth [1,2]. Chemical composition of a particular kerogen differs as a function of the source microrganisms that participated to the sediment and may be classified into three categories [3]. Type I kerogen, produced by algae or eventually bacteria and is the less abundant; type II, derived from other aquatic organisms (phytoplankton and zooplankton); the most common on Earth is type III, generated from organic plant matter. To the best of our knowledge, this work demonstrates for the first time the detection of natural organic matter in different rock of oil shales with a total organic carbon content between (2.78 % and 15.06 %) using LIBS under Martian conditions. A linear correlation was found between the net CN intensity and the concentration of total organic material of the samples under CO2 and Martian atmosphere. The fact that natural organic matter can be detected and characterized by LIBS in this kind of sedimentary rock – known for suggesting the existence ancient life - through its emitting species such as CN or C2 is of great relevance in astrobiology. Results presented here, may provide essential understanding on the search for biosignatures on Mars and for the development of planetary exploration strategies.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec