Reflectance Spectroscopy of Palagonites, Aluminous Phyllosilicates and Ferric Oxides as Analog MAterials for Martian Bright Soil

Abstract

Visible and near infrared reflectance spectra of mixtures containing Hawaiian palagonitic soils, aluminous phyllosilicates and ferric oxides have been studied in order to evaluate the spectral properties of bright regions on Mars. Reflectance spectra of bright Martian soils exhibit an absorption band near 2.2 muem indicating a small content of crystalline aluminous clays. In order to simulate the appearance of the 2.2 muem band, diffuse reflectance spectra of mixtures with various wt-% of the components were measured. The 2.2 muem absorption band is discernible in these ternary mixtures with a depth of 1% in spectral contrast if the content of phyllosilicates increases up to 10-20 wt-%. These spectralanalyses imply that the presence of comparable concentrations of crystalline aluminous clays can not be excluded in the bright regionsof Mars.