Characteristics of aerosols phenomena in martian atmosphere from KRFM experiment data

Abstract

Photometric limb to limb profiles of Mars were obtained in 8 narrow bands between 315 and 550 nm from the Phobos-2 spacecraft. Tentative results of analysis are presented in terms of optical properties of the atmosphere and surface. Imaginary part of the refraction index æ from 0.0075 to 0.02 for 315 nm and from 0.005 to 0.01 for 550 nm was estimated for the “constant” dust haze, using Mie theory for spherical particles. These values of æ are in a few times higher than obtained by laboratory tests of terrestrial analogues including basalt, andesit and montmorillonite. Two explanations are possible: influence of irregular shape of particles and/or presence of some more absorbing substances ( as goethit ). Particle sizes a few tenths micron having refraction index 1.55 are compatible with the discussed model of the “constant” haze. Full shape of the near equatorial photometric profile on 550 nm can be explained by the slightly absorbed atmosphere ( with the optical depth 0.4 and imaginary part of the refraction index 0.0075 ). Icy particles with the same average sizes as in the haze (r m=0.4 microns) but with more narrow size distribution can explaine the bright spot above the Arsia Mons. Optical depth τ =0.1 and column mass density 7·10 −5 g cm −2 of the icy clouds were evaluated.