The proposed project will be the first extended vision of upper atmospheric aerosols, from their production in ionized reactive media, to their evolution in the lower atmospheric layers when sedimenting to the surface (Figure 1). The study of the aerosol production in the upper atmosphere is presently a highly competitive field. The possible aging of the aerosols has however never been considered yet, whereas it may impact the whole atmospheric system. Three successive tasks are considered in the present project to describe the possible evolution of the aerosols:
1/ their production in upper atmospheric conditions,
2/ their aging by bombardment of charged particles in the upper atmosphere,
3/ their aging by UV radiation, and/or coating of condensable species at lower altitudes. The novelty of the atmospheric integrated approach requires the development of a new methodology.
The successive sequences will be experimentally simulated in chemical reactors combining synchrotron and plasma sources. The interpretation of the experimental results will be moreover supported by a modelling of the processes.
During the first 18 months of the project,
- First we developed most part of the instrumentation required for the project: we developed a VUV la source to simulate Titan's photochemistry in its ionosphere (article Tigrine et al. 2016), and we bought and installed ion mass spectrometers on our two reactors,
- Secondly we worked on a subtask of task 1, the chemical composition of aerosols produced in a plasma reactor mimicking Titan's ionospheric chemistry. Several important results were found involving the first molecular identifications in this complex material (Da Cunha et al. 2016, Gautier et al. 2016).
-Then we performed preliminary experiments to adress Task 2 : we analyzed the chemical composition of two solid phases produced in the same plasma environment, but exposed to different plasma durations (Carrasco et al. 2016).
-Finally we optimized an analytical method for the analysis of Titan's aerosols in the framework of a future space mission to Titan (Morisson et al. 2016)
