ExoMars Raman Laser Spectrometer RLS, a tool to semi-quantify the serpentinization degree of olivine-rich rocks on Mars

TL;DR

This study assesses the effectiveness of the ExoMars Raman Laser Spectrometer in identifying and semi-quantifying serpentinization in olivine-rich rocks on Mars, demonstrating high accuracy and detection capabilities in terrestrial analogues.

Contribution

The paper introduces calibration curves and validation results showing RLS's ability to detect serpentine and olivine with high precision, enhancing Mars exploration tools.

Findings

RLS successfully identified major mineral phases in analogues.

RLS detected minor compounds not seen by NIR and XRD.

Calibration curves showed high correlation (R2 > 0.999) with low uncertainty.

Abstract

We evaluate what will be the effectiveness of the ExoMars Raman Laser Spectrometer (RLS) to determine the degree of serpentinization of olivine-rich units on Mars. We selected terrestrial analogues of martian ultramafic rocks from the Leka Ophiolite Complex (LOC) and analyzed them with both laboratory and flight-like analytical instruments. We first studied the mineralogical composition of the samples (mostly olivine and serpentine) with state-of-the-art diffractometric and spectroscopic laboratory systems. We compared these results with those obtained using our RLS ExoMars Simulator. Our work shows that the RLS ExoMars Simulator successfully identified all major phases. Moreover, when emulating the automatic operating mode of the flight instrument, the RLS ExoMars simulator also detected several minor compounds, some of which were not observed by NIR and XRD. Thereafter, we produced RLS dedicated calibration curves (R2 between 0.9993 and 0.9995 with an uncertainty between 3.0% and 5.2% with a confidence interval of 95%) to estimate the relative content of olivine and serpentine in the samples. Our results show that RLS can be very effective to identify serpentine, a scientific target of primary importance for the potential detection of biosignatures on Mars the main objective of the ExoMars rover mission.