The M3 project: 3 – Global abundance distribution of hydrated silicates at Mars

Abstract

This paper is the third paper of a series that provides the modal mineralogy of the Martian surface (M3 project) at the global scale using near-infrared hyperspectral imagery. Numerous locations at the surface of Mars have previously been identified to harbor hydrated minerals which offer unique insights on the past water activity at the red planet. A radiative transfer model has been used to reproduce the spectra of these locations, based on the OMEGA instrument (Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité). Here we present the methodology applied to derive the hydrated quantitative composition and the first global compositional maps of hydrated minerals at Mars. Millions of spectra have been modelled to extract the modal composition of the hydrated locations, excluding sulfate-rich units. The lithology is summarized with 11 compositional maps of hydrated minerals at global scale at a sub-kilometer resolution. The hydrated mineralogy is dominated by an end-member of Fe-hydroxide, Fe- and Al-phyllosilicates and Fe/Mg micas which have on average an abundance >6 vol% and are spread globally on the identified regions. Locally, spots with high abundance (>20 vol%) of Al-smectite and Chlorite are also identified. The abundance of hydrated minerals is highest in Marwth Vallis, Nili Fossae and Meridiani Planum. However, the primary minerals almost always account for more than 50% of the composition. The modelling offers an opportunity to do local analysis of prospective landing sites and prepare for the upcoming landed missions. In the landing site for the ExoMars2022 and Mars2020 rovers, the obtained composition is in agreement with the expected detected mineralogy which demonstrates the robustness of the model and also offers a representation of the compositional variability. These global maps open the way to follow-up studies that will provide an in-depth characterization of the compositional gradients in local settings. Additionally, these compositional maps can 1) be used to calculate the water content namely potential amount of water stored within the quantified minerals and 2) provide information about the ISRU potential.