Quantitative compositional analysis of Martian mafic regions using MEx/OMEGA reflectance data: 1. Methodology, uncertainties and examples of application

François Poulet , J.-P. Bibring , Y. Langevin , J.F. Mustard , N. Mangold , M. Vincendon , B. Gondet , P. Pinet , J.-M. Bardintzeff , B. Platevoe

The Mars Express Observatoire pour la Minéralogie, l'Eau, les Glaces et l'Activité (OMEGA) collected an unprecedented visible and near-infrared hyperspectral dataset covering the low albedo regions of Mars. We investigate the ability to infer modal abundance of surfaces of these regions from a radiative transfer model developed by Shkuratov et al. [Shkuratov, Y., Starukhina, L., Hoffmann, H., Arnold G., 1999. Icarus 137, 235–246] and adapted to basaltic surfaces by Poulet and Erard [Poulet F., Erard, S., 2004 J. Geophys. Res. 109(E2)]. From OMEGA measurements of mafic surfaces, we develop several sensitivity tests to assess the extent to which the model can be applied to predict pyroxene composition (high-calcium phase and low-calcium phase), abundance of almost neutral components (plagioclase) in the near-infrared wavelength as well as grain sizes, by using a library of selected end-members. Results of the sensitivity tests indicate that the scattering model can estimate both abundances and grain sizes of major basaltic materials of low albedo regions within uncertainties ( to 15 vol. %). The model is then applied to data from dissected cratered terrains located in Terra Meridiani. The derived grain size including uncertainties is in the 50-500 μm range. This is consistent with the thermal inertia and albedo of this region, which indicates a fine sand-sized surface with little dust. The abundances of plagioclase (43-57%) and pyroxenes (, including of low-calcium phase) are in good agreement with previous basalt-like compositions of low albedo regions from thermal infrared spectral measurements. The method presented in this paper will provide a valuable tool for evaluating the modal mineralogy of other mafic regions of Mars observed in the near-infrared wavelength range.

Mots clés: Mars; Surface; Mineralogy; Infrared observations; Spectroscopy

François Poulet, J.-P. Bibring, Y. Langevin, J.F. Mustard, N. Mangold, et al.. Quantitative compositional analysis of Martian mafic regions using MEx/OMEGA reflectance data: 1. Methodology, uncertainties and examples of application. Icarus, 2009, 201 (1), pp.69. ⟨10.1016/j.icarus.2008.12.025⟩. ⟨hal-00524854⟩