ETD

• Biofirme
• Biosignatures
• Cheyava Falls
• Condizioni Marziane simulate
• Deep-UV Raman Spectroscopy
• Geobacter metallireducens
• Leopard spots
• Magnesium Carbonate
• NASA Mars 2020
• Oxidative Stress
• Perchlorates
• Simulated Martian Conditions
• Spettroscopia DUV Raman
• Stress ossidativo

This research evaluates the preservation and spectroscopic detectability of potential biosignatures under simulated Martian conditions. The metal-reducing bacterium Geobacter metallireducens was selected as a terrestrial analog due to its potential role in forming the reduction fronts recently identified at the "Cheyava Falls" rock target by the Perseverance rover, representing the most promising potential biosignature discovered on Mars. Samples of pure biomass and 10 wt.% adsorbed onto a magnesium carbonate matrix, with and without 1 wt.% perchlorates, were exposed to -60 °C, 6 mbar of CO2 and UV radiation for 6 hours (equivalent to at least 9 Sols). Degradation was monitored via DUV-Raman spectroscopy (SHERLOC analog) and biochemical assays (TBARS and Western Blot). Biochemical analysis revealed severe oxidative stress on the lipid membranes. However, DUV-Raman spectroscopy demonstrates that the biological signatures of Geobacter metallireducens are preserved. This stability is guaranteed by the photoprotective shield of the mineral matrix, which scatters UV rays, and by the cryogenic temperatures, which slow down the perchlorate oxidative kinetics. The results confirm that biosignatures remain stable and detectable by SHERLOC for at least 9 Martian Sols, amply covering the 1-Sol technical limit required for the rover. Finally, the extreme recalcitrance of the lyophilized biomass highlights the need for optimized extraction protocols.