Raman spectroscopy and planetary exploration: Testing the ExoMars/RLS system at the Tabernas Desert (Spain)

ExoFit trials are field campaigns financed by ESA to test the Rosalind Franklin rover and to enhance collaboration practices between ExoMars working groups. During the first trial, a replicate of the ExoMars rover was remotely operated from Oxfordshire (United Kingdom) to perform a complex sequence of scientific operation at the Tabernas Desert (Spain). By following the ExoMars Reference Surface Mission (RSM), the rover investigated the Badlands subsoil and collected drill cores, whose analytical study was entrusted to the RLS (Raman Laser Spectrometer) team. The preliminary characterization of core samples was performed in situ through the RLS Engineering and Qualification Model (EQM-2) and the Raman Demonstrator (RAD1), being this a new, portable emulator of the RLS. In situ results where then complemented by laboratory analysis using the RLS ExoMars simulator and the commercial version of the Curiosity/CheMin XRD system. Raman data, obtained by closely simulating the operational constraints of the mission, successfully disclosed the mineralogical composition of the samples, reaching the detection of minor/trace phases that were not detected by XRD. More importantly, Raman analysis detected many vibrational peaks potentially emitted by organic functional groups, thus suggesting the presence of microorganisms in the arid sub-surface of the Tabernas Desert. In light of the forthcoming ExoMars mission, the results here presented proves that RLS could play a critical role in the characterization of Martian sub-surface environments and in the analytical detection of potential traces of live.