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Protein preservation in martian regolith analogues under a simulated Mars surface environment

Presentation #108.08 in the session Astrobiology and Origins of Life (Oral Presentation)

Published onOct 23, 2023
Protein preservation in martian regolith analogues under a simulated Mars surface environment

The preservation of organic biosignatures in the Martian surface is likely to be impaired by several factors, the most prevalent of them being the lack of both a thick atmosphere and a magnetosphere, and the oxidative pressure exerted by the regolith itself. The absence of a thick atmosphere in Mars means that the practical totality of the UV spectrum reaches the surface. The energetic regions of this spectrum (UVB and UVC) are highly associated with the oxidative stress that promotes organic matter degradation, and are particularly damaging to aromatic residues. This stress makes aromatic-containing organic matter, like proteins and DNA, particularly susceptible to photolytic or chemical degradation. Proteins are extremely heterogeneous and their varied amino acidic composition makes them good targets of preservation studies.

To assess to which degree are proteins protected from UV irradiation when adsorbed to the martian regolith, we spiked bovine serum albumin (BSA), a commonly used model protein, into two commercially available martian regolith simulants (MMS-2 and MGS-1) and subjected them to UVB irradiation under several atmospheric and humidity conditions. Samples were then hydrolized through MSA acid hydrolysis, and the resulting amino acidic patterns were analysed and quantified through HPLC-FLD and OPA derivatizations, which allowed for the quantification of 16 different amino acid. We determined that 1 mm thick regolith layers could prevent most UV-induced damage when compared to directly irradiated films. Irradiation of wet substrates, however, led to increased amino acid degradation in all conditions, although the presence of regolith still offered significant protection. There were also differences between regoliths, as MMS-2 was significantly more oxidative and could lead to UV-independent chemical alterations. It was also determined that Trp, Met, His and Tyr were the more unstable amino acids under UV irradiation.

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