The microphysics of the clouds of Venus: Results of the Pioneer Venus Particle Size Spectrometer Experiment

The results of the particle size spectrometer experiment on the Pioneer Venus sounder probe are presented. The vertical cloud structure is found to consist of three primary cloud regions of approximately 20 km total thickness suspended within an ubiquitous aerosol haze which extends more than 10 km above and below it. The three cloud regions are separated by sharp transition regions where both particle chemistry and microphysics exhibit change. The size distributions are multimodal in all cloud regions. Three size modes are observed in the middle and lower cloud, region which are composed of aerosol, H2SO4 droplets, and crystals. The crystals likely could be either sulphates or chlorides. We provide interpretations of the sources, growth characteristics, and fate of the particle species through a partitioning analysis of the LCPS size distribution data.