title: Photochemical activity of Titan's low-altitude condensed haze.
abstract: Titan, the largest moon of Saturn and similar to Earth in many aspects, has unique orange-yellow colour that comes from its atmospheric haze, whose formation and dynamics are far from well understood. Present models assume that Titan's tholin-like haze formation occurs high in atmosphere through gas-phase chemical reactions initiated by high-energy solar radiation. Here we address an important question: Is the lower atmosphere of Titan photochemically active or inert? We demonstrate that indeed tholin-like haze formation could occur on condensed aerosols throughout the atmospheric column of Titan. Detected in Titan's atmosphere, dicyanoacetylene (C₄N₂) is used in our laboratory simulations as a model system for other larger unsaturated condensing compounds. We show that C4N2 ices undergo condensed-phase photopolymerization (tholin formation) at wavelengths as long as 355 nm pertinent to solar radiation reaching a large portion of Titan's atmosphere, almost close to the surface.
authors.affiliation: Jet Propulsion Laboratory, Science Division, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, California 91109, USA. murthy.gudipati@jpl.nasa.gov
authors.forename: Murthy S
authors.initials: MS
authors.lastname: Gudipati
authors.forename: Ronen
authors.initials: R
authors.lastname: Jacovi
authors.forename: Isabelle
authors.initials: I
authors.lastname: Couturier-Tamburelli
authors.forename: Antti
authors.initials: A
authors.lastname: Lignell
authors.forename: Mark
authors.initials: M
authors.lastname: Allen
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