Abstract EANA2025-54

Mars is a priority target for current and future space missions, including astrobiological exploration with the search for traces of extinct or existing life as one of the main objectives. The harsh Martian environment poses difficulties to the preservation of organic molecules due to rapid degradation processes such as oxidation and photolysis, intensified by the planet's thin atmosphere and high levels of solar radiation. The search for organic biosignatures on Mars will focus on identifying the precise molecular fingerprints of survival due to the photodegradation process by the destructive environmental radiation [1-2]. Solar ultraviolet can induce photochemical degradation of organic compounds, so it is crucial to study this process in order to search for conserved functional groups. Therefore, understanding the chemical processes of key organic compounds such as nucleosides in this deleterious environment became a priority. It is then crucial to understand the stability and degradation of biomolecules [3], including nucleobases, in both space and planetary environments. In this context, the characterisation of isolated molecules, and their behaviour in a reactive environment, is the first step towards understanding the properties of complex molecular materials. The harsh conditions on Mars can induce photochemical degradation of organic compounds, so it is crucial to understand the chemical processes that take place in simulated Mars conditions. Our target molecule is adenosine, which is one of the four nucleosides building blocks to DNA and RNA, essential for life. Modification of its structure or chemical functionalities is likely to affect its biological activity dramatically.

Therefore, we have performed several experiments inside the Planetary Atmosphere and Surfaces Chamber (PASC) simulation chamber [4], considering UV irradiance exposure in the range 200 to 400 to cover Mars conditions and 7 mbar CO2 atmosphere. PASC is an ideal platform for the laboratory study of the evolution of these molecules under simulated Mars conditions, discriminating different physico-chemical environmental parameters and their impact on molecular chemistry individually or jointly. To gain an in-depth understanding of the chemical changes in adenosine and its adenine and ribose fragments associated with exposure to the Mars simulation, we have applied a battery of spectroscopic techniques, before and after exposure to the Martian environment conditions, such as infrared (IR), Raman and X-ray photoemission spectroscopy (XPS). The results confirmed the formation of a new chemical functionality in the adenosine and adenine samples under Martian conditions and the role of the sugar moiety (ribose) in the stabilisation of the nucleoside system when irradiated with ultraviolet light. These studies help to understand the relevance of the characterised biomolecules in the planetary context, which physico-chemical parameters are crucial in molecular degradation and which chemical functionalities confer stability to the system, of great significance in prebiotic chemistry and planetary exploration.

References:

[1] Sharma, S., Roppel, R.D., Murphy, A.E. et al. Nature 619, 724–732 (2023).

[2]   C. Freissinet,D.P. Glavin,P.D. Archer,S. Teinturier,A.et al., Proc. Natl. Acad. Sci. U.S.A. 122 (13) (2025).

[3] Cueto-Diaz, E. Galvez-Martinez, S. Colin-Garcia, M. and E. Mateo-Marti*E., Life, 13(4), 908 (2023)

[4]   E. Mateo-Martí*, E. Prieto-Ballesteros, O. Sobrado, J. Gómez-Elvira, J. and Martín-Gago, J. A.  Meassurement and Science Technology, 17, 2274 (2006)

 

Keywords: Astrobiology, Biomolecules, Planetary Simulation Chamber, Mars, Spectroscopies.