Assessing the biogenic source of organic molecules in lava tubes: Potential for astrobiology and palaeoclimate

Comunicación oral presentada en el 1st European Meeting on Geomicrobiology of volcanic caves. días 2-3 de marzo de 2023 celebrado en la Casa de la Ciencia-CSIC de Sevilla

Over the last decade, terrestrial lava tubes have greatly attracted the attention of the scientific community due to the presence of similar features on the Moon and Mars. Characterized by stable physicochemical conditions, these subterranean environments harbor highly diverse microbial life-forms that interact with minerals. This result in the preservation of traces of microbial features or activity in the rock record, recognized as biosignatures. They comprise one of the most important tools for understanding the origin, evolution, and distribution of life on Earth and possibly on other planets. This communication will address the work that has been carried out in the framework of the MICROCENO and TUBOLAN projects, to accurately identify biosignatures preserved in speleothems from lava tubes of Selvagens Islands (Portugal) and Lanzarote (Spain). In this sense, cutting-edge chromatography, and mass spectrometry techniques (e.g., GC/MS, Py-GC/Q-TOF, Py-CSIA) have been employed for an in-depth biogeochemical characterization of the samples. The characteristic pattern of short-chain n-alkanes was related to a microbial origin, and was confirmed by the presence of short-chain methylated fatty acids (C<20). In contrast, the existence of vegetation biomarkers (e.g., lipid compounds of high molecular weight) preserved in the speleothem samples suggested the existence of lixiviation processes from the surface. Stable isotope analysis depicted δ13C values ranging between -24 ‰ and -46 ‰, indicating the influence of C3 plants and the existence of methanogenic microorganisms, respectively. These compounds are organic biosignatures valuable for geomicrobiology, astrobiology, and paleoenvironmental reconstruction.

Acknowledgements: The Portuguese Foundation for Science and Technology (FCT) is acknowledged for funding the MICROCENO project (PTDC/CTA-AMB/0608/2020). The Spanish Ministry of Science and Innovation from the Spanish State Agency (AEI) is also acknowledged for funding the TUBOLAN project (PID2019-108672RJ-I00). Vera Palma acknowledges the support from the Research Scholarship for Master within the scope of the project MICROCENO

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