Composition Analysis of Martian surface by near-infrared imaging spectroscopy

Abstract

Reflectance Spectra of Mars obtained by the imaging spectrometer (ISM) in the wavelength range from 0.76 to 3.16 muem allows us to study the surface composition. This information is given by typical absorption features in the spectra of the Martian soil minerals. A band of atmospherc CO2 near 2 muem was used to compute relative heigths of the surface and the air mass factor. The most prominent spectral characteristics related to the Martian surface are found to be variations in infrared brightness, of the continuum slope, of absorption features between 2.2 and 2.5 muem, of a bound water band at 3 muem, and of a complex Fe+, Fe3+ -absorption near 1 muem. It hasbeen shown that the depth of these factors is not correlated with theair mass factor. The bands at 2.2 and 3 muem can be used to study the variation of surface hydratation. The 3-m-band is a comlex feature of bound water. There is an indication that the 2.2-muem- signature may be attributed to an A-OH stretching mode of hydrated minerals. The variation of spectral characteristics is shown in spectral maps and the comparison of these maps with surface brightness, laboratory measurements, and geological units on Mars allows us to discuss the variation of surface composition. Spectra of the Tharsis Montes region show high spectral contrasts in the 2.2-muem-band. This bright material seems to be more hydrated. Inthe dark areas of Valles Marineris and Syrtis Major Planitia a broad ferric-ferrous absorption occurs.