Groundbased Imaging Spectroscopy of Mars in the Near-Infrared: Preliminary Results

Groundbased near-infrared (1.30-4.05 μm) imaging spectroscopic measurements of Mars were obtained during the 1990 opposition to define the spectroscopic variability of the Martian surface and atmosphere. Surface albedo features at wavelengths less than 3.5 μm are almost identical in form and contrast to the classical albedo markings observed in the visible, with typical bright/dark contrasts of 2.0 to 3.0. Poleward of 45°N and 70°S, the reflectance at wavelengths between 2.9 and 3.3 pm was 60-90% lower than at mid- and equatorial latitudes, indicating the presence of atmospheric or surface water ice. Maps of absorption band depths in the 1.9-2.4-μm region show significant spectral variability from region to region on Mars. Comparisons with Viking measurements and radiative transfer model results reveal that most of this variability is correlated with topography, albedo, and emission angle differences but some of it appears to be related to surface mineralogic or airborne dust variations.