Biosignature Stability under Martian Surface Conditions: Implications for Sample Analysis by the Rosalind Franklin Rover

The 2028 ESA/NASA Rosalind Franklin Rover will search for signs of past and present life in the shallow subsurface of Mars. It is crucial to understand how minerals and any biosignatures uncovered during these sampling activities might be changed and can be identified under today’s Martian conditions. This preliminary study explored the effects of cryodessication, induced by the sub-zero, near-vacuum conditions on the Martian surface, on Ca-sulphate, the SOPHIA Mars soil simulant and an Antarctic microbial mat collected during the Scott Expedition. Powdered samples were analysed via Fourier Transform Infra-Red (FTIR) and Visible-Near-Infrared (Vis-NIR) spectroscopy, frozen, and then placed in a lyophilizer maintained at -63.4 °C with a vacuum of 1.182 mbar for 1 hour and 72 hours. After 1 hour, Mars-like sublimation processes were not fully completed within the three Mars analogue samples yet helped to increase the spectral intensity of the mineralogical, hydration, and organic features within the samples. After 72 hours exposure, hydration- and organic-induced spectral bands began to decrease in intensity and detectability, with some features now removed. Understanding how sampling activites and subsequent environmental exposure affects the mineralogical and organic content of samples, and how to spectrally identify these features using rover instrumentation, is vital in assessing the reliability of the data uncovered, the differences between the subsurface and surface environments at Oxia Planum, and therefore the environmental and biological interpretations made.