Quantitative compositional analysis of Martian mafic regions using the MEx/OMEGA reflectance data: 2. Petrological implications

François Poulet , N. Mangold , B. Platevoet , J.-M. Bardintzeff , V. Sautter , J.F. Mustard , J.-P. Bibring , P. Pinet , Y. Langevin , B. Gondet , A. Aléon-Toppani

The primary objectives of this paper are to determine the modal mineralogy of selected low albedo terrains of different ages ranging from Noachian to Amazonian exposed on the surface of Mars. This analysis is conducted using the spectral modelling of the Observatoire pour la Minéralogie, l'Eau, les Glaces, et l'Activité (OMEGA) reflectance data. Results from this work are consistent with the major results of previous spectroscopic studies: plagioclase (40–60% in volume) and high calcium pyroxene (20–40%, HCP) are the dominant minerals of the most regions. Low calcium pyroxene (10–15%, LCP) and minor amounts of olivine are also present. The oldest terrains are characterized by the largest amount of LCP and the lowest concentration of plagioclase. These overall compositions are consistent with two-pyroxene basalts. The particle sizes are in the range of a few hundreds of micrometers, which is in good agreement with the thermal inertia of the Martian low albedo regions. In the region around the Nili Fossae, localized concentrations of olivine up to 40% with millimetre particle size similar to picritic basalts observed in situ by the Spirit rover in the Gusev crater are inferred. Chemical compositions are calculated for the first time from OMEGA spectra. They are quite consistent with Gusev rocks and Shergottite compositions but they appear to be significantly SiO-poorer than Thermal Emission Spectrometer data.

Mots clés: Physical Sciences

François Poulet, N. Mangold, B. Platevoet, J.-M. Bardintzeff, V. Sautter, et al.. Quantitative compositional analysis of Martian mafic regions using the MEx/OMEGA reflectance data: 2. Petrological implications. Icarus, 2009, 201 (1), pp.84. ⟨10.1016/j.icarus.2008.12.042⟩. ⟨hal-00524857⟩