Abstract EANA2026-42

Approximately 4 Ga ago, Mars presented habitable environmental conditions associated with the presence of liquid water on its surface. However, the surface became uninhabitable during the Hesperian period, due to a decrease in atmospheric pressure and subsequent loss of surface liquid water. Nevertheless, biosignatures of past life (e.g., pigments) may still be preserved in ancient rocks [1]. Due to Mars’ low-pressure atmosphere and lack of a magnetosphere, the surface has been heavily irradiated by Solar Energetic Particles (SEPs) and Galactic Cosmic Rays (GCRs), which are able to penetrate multiple layers into the subsurface [2]. However, shielding at depth could still preserve certain organic molecules (e.g., amino acids) despite several Ga of this ionizing radiation [3]. Therefore, the upcoming Rosalind Franklin rover of the ExoMars mission is equipped with a drill capable of sampling up to two meters below the surface [4].

This work aims to simulate and evaluate the combined effects of SEP and GCR irradiation over several Ga on Mars analogue rocks enriched in organic matter, in order to investigate the protective role of different minerals in biosignature preservation. Monte Carlo simulations of Martian surface and subsurface radiation environments are currently being performed using the GEANT4 toolkit [5], with atmospheric pressure and column depth, as well as regolith composition and density being a few of the main variable parameters. For validation purposes, the simulation framework developed will also be tested against available data collected by the RAD (Radiation Assessment Detector) instrument onboard the Curiosity rover, as done by [6]. The output from these numerical simulations will guide the design and validation of upcoming laboratory experiments, by providing detailed information on energy deposition and dose profiles within the Martian regolith. Furthermore, analogue samples from the ISAR (International Space Analogue Rockstore) collection (Orléans, France), along with synthetic organo-mineral mixtures representative of Martian regolith, will be irradiated with protons at the CEMHTI Pelletron light-ion accelerator (CNRS, Orléans) and characterized in situ as well as ex situ. In situ analyses will rely on the use of an in-house developed Raman spectrometer [7], complemented by Ion Beam Analysis.

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