Isotopic fractionation of trace molecules in the atmosphere of Titan

High precision measurements of the isotopic composition of H, C, N and O in several molecules in the atmosphere of Titan have recently been obtained by the Cassini-Huygens instruments. We developed a one-dimensional photochemistry-transport model for methane, ethane, water, nitrogen and their isotopologues. Our model identifies the important physical, photolytic and chemical processes that control the isotopic fractionation of these species in Titan’s atmosphere. The model successfully accounts for the recent observations. Implications of our current model for understanding the chemical evolution of the atmosphere of Titan are discussed. Subject headings: planetary systems—radiative transfer—atmospheric effects— planets and satellites: individual (Titan) — methods: numerical 1