Estudo da detecção de biomarcadores em meteoritos expostos a biomoléculas em ambientes marcianos simulados através da espectroscopia Raman

Abstract

The search for extraterrestrial biosignatures is fundamental to astrobiology, especially in the context of Martian exploration. However, the stability and detectability of these biomolecules in hostile environments remain significant challenges. Raman spectroscopy is a powerful tool for biomolecule detection due to its vibrational specificity, but its signal can be weak, particularly at low concentrations or in complex matrices. To overcome this limitation, the surface-enhanced Raman scattering (SERS) spectroscopy becomes indispensable, allowing for the sensitive detection of biosignatures on meteorite substrates. This work investigated the stability of biomolecules (adenine, β-carotene and L-tryptophan) adsorbed on AgNPs and AuNPs on fragments of the Martian meteorite NWA12965. The samples were subjected to simulated Martian environmental conditions, including ultraviolet (UVA/UVB and UVC) radiation and reduced pressure (vacuum). The AgNPs and AuNPs were characterized by UV-VIS spectroscopy and the evolution of biomolecules on the meteorites was monitored by SERS spectroscopy. The characterization of the NWA12965 meteorite revealed that its composition is predominantly pyroxene. The cleaning with aqua regia did not significantly alter its Raman spectrum, suggesting that persistent bands might be intrinsic or due to amorphous carbon contamination. SERS spectroscopy proved effective in detecting biomolecules on the meteorite. Photodegradation results from UVA/UVB and UVC revealed that all three biomolecules are highly susceptible to degradation. Adenine, β-carotene and Ltryptophan exhibited progressive photodegradation under UV irradiation, with new bands, assigned to photoproducts, emerging or characteristic bands disappearing. Under reduced pressure conditions, the interaction of the biomolecules with the nanoparticles and the mineral substrate showed distinct behaviors. Adenine showed a significant SERS signal intensification, followed by a slight decay, indicating some resilience. βcarotene experienced a loss in SERS signal efficiency. L-tryptophan, in turn, demonstrated that under reduced pressure, it can induce signal decrease and aggregation of AuNPs, altering its spectral patterns. These results indicate the fragility of essential biomolecules in simulated extraterrestrial environments, highlighting the challenges for their preservation and detection. Furthermore, the findings point to the complexity of interactions between biomolecules, metallic nanoparticles, and mineral substrates under environmental stress, providing crucial insights for future astrobiology missions and biosignature search strategies.