  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.
