PROPERTIES OF DUST IN THE MARS ATMOSPHERE - A REVISED ANALYSIS OF PHOBOS KRFM DATA/

During the 1989 Phobos 2 mission, photometric observations of the equa torial region of Mars were made in eight spectral bands in the range f rom 315 to 550 nm by the KRFM spectrometer. The first analysis of thes e data which aimed at extracting the optical properties of the atmosph eric dust (Moroz et al., 1993) used an approximate approach for the ra diative transfer, underestimating the effect of multiple scattering. T he present analysis of the same data corrects for this limitation with the use of a doubling/adding method. The new analysis yields comparab le values for the optical depth in the range 0.1-0.15. However, the im aginary part of the refraction index of the atmospheric particles almo st doubles: m(i) = 0.030 +/- 0.005 for 315 nm and m(i) = 0.012 +/- 0.0 03 for 550 nm, compared with 0.015 and 0.005 before, while it continue s to decrease as a function of wavelength. (C) 1997 Elsevier Science L td.