Analysis of weak surface absorption bands in the near-infrared spectra of Mars obtained by Phobos-2

Abstract

Reflectance spectra of Mars obtained by the imaging spectrometer ISM in the wavelength range from 0.76 to 3.16 muem have been analyzed andprevious studies have been reviewed. A new method of error calculation has been developed that enables improved interpretation of the Martian surface composition from the ISM data. Based on this calculation criteria are defined to evaluate the spatial variation ofweak surface absorption bands. Spectral variables have been calculated taking into account the viewing geometry and atmospheric absorptions. Variations in the spectral properties of Mars are shown in spectral maps of characteristic target areas including the Ascraeus Mons volcano and Lunae Planum. Spatial variation in the depth of a weak feature at 2.2 muemhas been studied for these areas. Spectral subunits have been devined and are discussed in relation to the surface composition of Mars.