^1,2Miguel Arribas Tiemblo,¹Pedro Rayo,¹María-Paz Martín-Redondo,¹Felipe Gómez
Journal of Geophysical Research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2025JE009070]
¹Centro de Astrobiología (CAB), CSIC-INTA, Madrid, Spain
²Universidad de Alcalá de Henares (UAH), Madrid, Spain
Published by arrangement with John Wiley & Sons

Amino acids are an extremely heterogeneous group of biomolecules essential for life on Earth. Their biosignatures are expected to be easily degraded on the Martian surface as the absence of a thick atmosphere and a magnetosphere leads to most of the solar radiation directly reaching its surface. To determine the preservation of amino acids in the Martian regolith, and their detectability, we exposed protein-sourced and free amino acids to UV-B radiation. This was done while in contact with different particle size ranges of two Martian regolith simulants. Bulk analysis through High Performance Liquid Chromatography (HPLC) showed that UV-B radiation led to little damage across all samples, mainly targeting sensitive amino acids like tyrosine, histidine, tryptophan and methionine. The two Martian simulants were divided into five particle size ranges. Smaller particles (<0.045 mm) led to higher recoveries than bigger ones (>0.500 mm), likely through their high specific surface area. Raman spectroscopy offered localized surface information, which HPLC was unable to. One of the simulants (MMS-2) is rich in iron oxides like hematite, which likely prevented any detection by absorbing the excitation wavelength of the laser. Irradiation also led to widespread loss of signal of all amino acids. Overall, the limitations of both techniques were compensated by each another, which allowed for the precise characterization of the chemical alterations suffered by amino acids in these conditions.