Séminaire LATMOS, OVSQ, Amphithéâtre Gérard Mégie, vendredi 8 avril à 11H: Panayotis Lavvas (LPL, University of Arizona): "Photochemical aerosols: Production, evolution, and their role in Titan's atmosphere". Titan's aerosols are a result of the complex photochemistry that takes place in the satellite's atmosphere. The Voyager missions identified the main impact of aerosols in the stratosphere, but the Cassini/Huygens mission has revealed a far more complex and intriguing picture: aerosols are detected at as high altitudes as in the thermosphere, they form multiple detached layers above the stratospheric main haze layer, they extended all the way to the surface in the main haze layer, and eventually cover the satellites surface. I will present an overview of the latest observations regarding the aerosols properties as revealed by the Cassini/Huygens instruments, and furthermore discuss recent simulations for the aerosol production and evolution. These demonstrate the feedback of aerosols in the gas phase chemistry of the atmosphere, and their role in cloud formation in the lower atmosphere.