Developing a 3D generic photochemical-GCM. Transit spectroscopy simulation and observability.

The next generation of space and ground-based telescopes (JWST, ARIEL, ELTs) should give us improved transmission/emission spectra for a large diversity of exoplanets, allowing to probe their atmospheric composition. For a better understanding of this data, atmospheric models taking into account photochemistry are required. Several 1D atmospheric models have been developed and can be applied to a diversity of exoplanets. However, taking into account 3D geometry for the analysis can become necessary due to the interplay between atmospheric circulation, chemical kinetics, and the potentially very steep temperature gradient between the day and night sides. In this context, we developed a generic (photo)chemical module including photochemistry online for the LMDZ generic 3D Global Climate Model (GCM). Using this new development we performed simulations of Trappist-1e atmosphere to observe M-dwarf stellar spectra consequences on Earth like atmosphere. Considering the different stellar UV activity of M-dwarf, photochemistry could be highly impacted. We found that Trappist-1e gathers favorable conditions to sustain an ozone layer one order of magnitude more abundant than Earth. Transmission spectroscopy simulations and retrievals show that we would need close to 50 transits with the JWST to have a significant detection of the 9.6 um ozone band