The upper atmosphere of TITAN: Photochemistry in the Vacuum Ultra-Violet (VUV)

TITAN's upper atmosphere

The Cassini-Huygens space mission around Saturn has revealed an intense and unexpected photochemistry in the highest atmospheric layer of the satellite Titan. The reactivity from the photolysis of both molecular nitrogen (N2) and methane (CH4) is responsible for the formation of solid organic aerosols whose mass is larger than 1000 uma and have a high exobiological interest. The phenomenon involved is the still significant contribution of the VUV solar photons, with a wavelength below 100 nm, which are the only ones able to photolyse, or even ionize, N2. Unfortunately, the performances of the Cassini instruments do not allow the access to the chemical composition of the high atmosphere, which has become one of the main issues of current exobiology.

The APSIS Experiment: Atmospheric Photochemistry SImulated by Synchrotron

The APSIS platform is a laboratory simulation of the upper atmosphere of Titan using VUV light as an energy source. We can use the DESIRS beamline at the synchrotron SOLEIL as a VUV light supply; but in parallele we are developping our own VUV source at LATMOS.

More information about the APSIS reactor can be found with Peng et al. (2013) JGR-planets & Carrasco et al. (2013) J synch rad

Besides, we are working on the development of ultra-thin VUV-transparent windows which will allow us to work with a closed gas cell but still get the wavelenghts we are interested in, e.g below 100nm. This project is supported by the French Space Agency (CNES).

My Thesis

I've started my thesis in October 2014 thanks to a grant delivered by the Universite Paris Saclay.

Most of the work is done at the LATMOS but I'm also spending approx. 1/3 of the time at the synchrotron SOLEIL facility.