Survivability of Biomolecules Under Energetic Processes for the Identification of Biosignatures on Mars

Missions on Mars have already demonstrated its past habitability (Arvidson et al., 2014; Fornaro et al., 2018a; Grotzinger et al., 2014) and the search for biosignatures, such as the identification of organic molecules, has become one of the main goals of exploration programs (Fornaro et al., 2020; Horneck et al., 2016). Specifically, data collected by the SAM instrument showed the presence of thiophenes, aromatics, aliphatic and thiol derivatives in the Murray and Sheepbed mudstones, similar to the analysis of the Tissint Mars meteorite (Eigenbrode et al., 2018). However, organics on the surface of Mars are continuously exposed to harsh environmental conditions. Among them, the UV and ion radiation is known for its critical implications on the organic matter present in the soil.

Thus, an understanding of the environment in which organic matter evolves on the Martian surface is important. Specifically, minerals play a crucial role in the processes experienced by organic molecules on Mars, influencing their chemical evolution. The preservation state of organic molecules is often regulated by their interaction with the mineral phase in which they are embedded. Investigations on the catalytic and protective properties of different Martian minerals under Mars-like conditions have been carried out (Fornaro et al. 2018b), who concluded that in several paleoenvironments on Earth, the long-term preservation of terrestrial biosignatures is attributed to sedimentary materials, in particular phosphates, silica, clays, carbonates and metalliferous materials. However, the simple classification of Martian minerals as catalytic or protective is not possible because the behaviour of minerals under Martian conditions depends on the organic molecules involved and their specific interactions with the mineral surface sites. It is therefore important to study the response of specific molecule-mineral complexes to UV and ion irradiation.

In this work, we investigated the likelihood that amino acids and fatty acids biomarker embedded in minerals would be preserved despite Martian chemical weathering by energetic irradiation, and therefore be observable by analytical techniques on board of Rosalind Franklin rover.

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