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Abstract EANA2026-10 |
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Stability of lipid-like organics under simulated Martian radiation
The search for remnants of life on Mars is hampered by the cumulative exposure of organic compounds to solar and cosmic radiation [1]. Under shallow burial, penetrating cosmic radiation can progressively alter beyond recognition molecular fossils from a potential Martian life, erasing some or all diagnostic information. We here present a study that may offer a partial solution to tackle this obstacle imposed by the Martian radiation environment.
In general, it is recommended to target biomarkers that are robust enough to endure in the billion-year-timescale the hostile conditions present in the shallow subsurface of Mars. In this context, hydrocarbon backbones of lipids are among the most resistant classes of organic molecules [2,3], and are ubiquitous in terrestrial living systems as integral components of cellular membranes. Thus, pure lipid-like compounds represent compelling astrobiological targets for Mars exploration missions. However, their radiolytic degradation pathways under high‑energy irradiation remain poorly constrained, especially for molecular architectures exhibiting unambiguous biogenic features. For that reason, it is crucial to establish well-defined mechanistic baselines on the radiolytic profiles of biomarkers of interest.
In pursue of underlying degradation mechanisms, we exposed five lipid-like organic compounds with different molecular architectures to gamma-radiation doses of up to 1300 kGy, corresponding to approximately 20 million years of surface exposure on Mars. Compounds comprised both abiotically plausible and unambiguously biological lipids, and were analyzed via gas chromatography coupled to mass spectrometry (GC-MS). Exposure to radiation quickly destroyed short and polyunsaturated organics, whereas biologically relevant longer carboxylic acids and ring-shaped molecules displayed higher resistance, and could potentially survive for millions of years on Mars.
To address detectability in the context of the Rosalind Franklin Mission [4], we further enhance the relevance of our analyses by employing a Flight Analogue System of the Mars Organic Molecule Analyser (MOMA) – the mass spectrometric package onboard the rover. Analyzing irradiated lipid-like organics with this pyrolysis-GC-MS setup provides a more realistic view of what the rover may encounter once in Oxia Planum. Overall, this study could significantly strengthen the scientific readiness for one of the most sensitive aspects of the mission: the search for recognizable molecular traces of life.
[1] A. A. Pavlov, G. Vasilyev, V. M. Ostryakov et al., Geophysical Research Letters, 39, L13202 (2012).
[2] J. J. Brocks and R. E. Summons, Treatise on Geochemistry, Elsevier, p. 63-115 (2003).
[3] G. Vinnichenko, A. J. M. Jarrett, J. M. Hope et al., Geobiology, 18, 5 (2020).
[4] J. L. Vago, F. Westall et al., Astrobiology, 17, 6-7 (2017).