Photolytic behaviour of methane at Lyman-α and 248 nm: Studies in the frame of a simulation program of Titan’s atmosphere (S.E.T.U.P.) Original Research Article

This paper first describes briefly some of the forefront global simulations of Titan’s atmosphere that have been carried out up to now. In these experiments, an initial gaseous mixture of N2/CH4 is submitted to a single energy source and the retrieved gas and/or solid phase(s) is/are analyzed by different techniques. The second section presents a new simulation program, named S.E.T.U.P., currently under development in our laboratory. In this program, an original experimental device will be used to perform simulation experiments. The specificities of this device are also discussed into details in the second part. Indeed, it will allow: (i) to improve the representativeness of such simulation experiments towards Titan’s atmospheric conditions. For the first time, the initial gas mixture will be submitted to both major energy sources that are responsible for the chemical evolution of Titan’s atmosphere: electrons and photons (248 nm). (ii) to perform an in situ diagnostic by means of time resolved spectroscopy. Qualitative as well as quantitative analysis will be performed in order to investigate the chemical mechanisms involved in the evolution of the gaseous mixture. In a third part, the paper reports some studies on the photolytic behaviour of methane at Lyman-α and at 248 nm. Indeed, such a work was necessary to validate the experimental device that will be used to carry out the Titan’s simulations in the S.E.T.U.P. program.