Infrared reflectance spectra of Martian analogues

Reflectance spectroscopy in the infrared is a powerful tool to characterise the optical properties of analogue materials for Mars. In this work we pre sent laboratory studies of four Martian analogues: calcite, montmorillonite , palagonite and andesite. Diffuse and specular reflectance and transmittan ce spectra in the LR are shown. The spectral effect produced by small grain s clung to the larger ones is analysed for calcite. Significant variations in the diffuse reflectance spectrum, especially in the reststrahlen region, are observed. The diffuse reflectance spectra of the other materials show the shift of the reststrahlen features with Si content in the materials. Op tical constants of andesite are retrieved, by using the Lorentz model, from the specular reflectance spectrum. These values are fundamental in perform ing modelling of the radiance coming from the planet Mars. (C) 1999 Elsevie r Science Ltd. All rights reserved.