Experimental Simulation Of Titan'S Stratospheric Photochemistry: Benzene (C6h6) Ices

We performed laboratory experiments to study the photochemical evolution induced by long-UV irradiation of benzene ices in Titan's atmosphere. The aim of this study was to investigate whether photo-processed benzene ices could lead to the formation of aerosols analogs to those observed in Titan's stratosphere. Prior to that, spectroscopic properties of amorphous and crystalline benzene ices were studied as a function of temperature, using infrared spectroscopy. UV photolysis experiments (lambda > 230 nm) of benzene ices led to the formation of volatile photo-products, among which fulvene is identified, and of a residue dominated by nu CH IR features, demonstrating that pure aromatic-based polymeric structures are not sufficient to explain the composition of Titan's stratospheric haze layer. However, we provide a characterization of long-UV-induced benzene-containing aerosol analogs, which will contribute to Titan's surface organics layer. These data are of prime interest in the context of the future Dragonfly space mission.