Remote sounding of the Martian dust from ISO spectroscopy in the 2.7 μm CO2 bands

This paper presents a study of Martian aerosols based on the spectral observations near 2.7 μm. Simulations by Titov et al. [Planet. Space Sci. 48 (2000) 67] showed that the depth and the shape of saturated 2.7 μm band of atmospheric CO2 are sensitive to the presence of aerosols. This allows one to determine the aerosol optical depth, the scale height, and optical properties from the spectral measurements in the band. For the first time this method is applied to two disk-averaged spectra of Mars recorded by the Infrared Space Observatory (ISO). The analysis implies existence of sharp absorption band in the dust spectrum between 2.7 and 2.8 μm that probably indicates the presence of phyllosilicates (for instance, montmorillonite) in the dust. The best fit to the ISO spectra is obtained in the model with column optical depth of 0.33±0.13. This value is in good agreement with simultaneous Mars Pathfinder and Hubble Space Telescope observations.