Preservation and detection of carotenoid pigments of Deinococcus radiodurans on mineral substrates under UV irradiation

Biosignatures (or biomarkers), such as carotenoids, derived from microorganisms serve as valuable indicators of past or present life within the geological record on planetary surfaces. This study investigates the resistance and preservation of carotenoid pigments from the poly-extremophilic bacterium Deinococcus radiodurans across various mineral substrates using Raman spectroscopy and diffuse reflectance in the UV–Vis range. Pigment-substrate mixtures were exposed to simulated conditions mimicking the surface of Mars, a UV-rich terrestrial environment, and space conditions at the Toroidal Grating Monochromator beamline of the Brazilian Synchrotron Light Laboratory. Our findings reveal that the topmost layers of the substrate act as protective shields against radiation, preserving biomolecules located a few hundred micrometers below the surface in all three simulated environments. This integrated approach offers a promising analysis protocol for an in situ search for molecular fossils on diverse planetary surfaces, eliminating the need for extensive sample preparation.