Laboratory analog experiments to support detection of organics on Mars by deep UV Raman spectroscopy

This thesis focuses on laboratory experiments with Martian analogs to support the identification of organic compounds through deep UV Raman spectroscopy, using NASA's Mars 2020 Perseverance rover in Jezero Crater, Mars. The studies aim to validate hypotheses regarding the nature of potential organic compounds detected with the SHERLOC instrument in the Quartier abrasion patch. Spectral Quartier analog samples were prepared using two polycyclic aromatic hydrocarbon (PAH) candidates: 9-Methylanthracene (9MA) and 1,3-Dihydroxynaphthalene (13DHN). These compounds were combined with anhydrite, the primary sulfate identified, and subsequently analyzed. The key findings are: 1) Measurement of the absorption cross-section, demonstrating resonant enhancement for both molecules at SHERLOC's wavelength. 2) Characterization of dilutions to validate a theoretical model, highlighting detection limits of 0.001% for 9MA and 0.0005% for 13DHN. 3) Evaluation of interference effects with insoluble organic matter (IOM), commonly found on Mars. 4) Study of the photostability of 9MA under Martian-like UV conditions, revealing a catalytic effect of anhydrite on its degradation and the likely formation of 9MA dimer phase. The results contribute to interpreting SHERLOC's ‘in situ’ data and support the search for evidence of past life on Mars. Future studies will explore a more complex mineral matrix that includes magnesium sulfate, that was also detected in Quartier and showed to possess protective properties with diverse organics.