AEROSOL COMPONENT OF THE MARTIAN ATMOSPHERE AND ITS VARIABILITY FROM THE RESULTS OF INFRARED RADIOMETRY IN THE TERMOSCAN PHOBOS-2 EXPERIMENT/

TWO thermal infrared images taken by the Termoscan/Phobos-2 radiometer at the morning and evening limbs of Mars are analysed. The retrieval of aerosol extinction coefficients from about 400 crosslimb brightness profiles yielded a two-dimensional distribution of the aerosol with a spatial resolution of similar to 2 km. The aerosol vertical structure in the morning consists of two components: one is an exponentially in creasing extinction from about 20 km down to the surface and the other is an aerosol layer located at 20-35 km altitude. In contrast, no aer osol layers were observed at the evening limb. In addition, the aeroso l extinction in the evening showed a trend to decrease in the lower 5 km near the surface. The differences between the morning and evening o bservations were interpreted as an indication of the formation of the ice hazes at 20-35 km and near the surface at night on Mars. (C) 1997 Elsevier Science Ltd.