Aerosols have a strong impact on the atmosphere of a planet and notably on its thermic balance. They modify in particular the radiation flux emitted and received by the planet. For example, the presence of photochemical haze in the high atmosphere of Titan triggers an anti-greenhouse gas effect responsible of a 9K decrease of the temperature at the surface (McKay et al 1991). Moreover, such solid particles can serve as condensation nuclei (Lohmann et al 2005) leading to the formation of clouds which influence significatively the climate.
However, aerosols are also chemical entities which interact with the atmosphere itself. This interaction can make their chemical composition evolve as well as their physical properties. Here, we investigate the chemical evolution of Super-Earth or Earth like exoplanet dry aerosols formed in the upper part of the atmosphere in a humid and oxidative environment like the Earth one. Studies have shown, thanks to IR and FTICR measurements, the existence of a progressive aging process on the solid matter with an increase of oxygen content with time (Maillard et al 2022). In this work, we try to focus more precisely on the mechanisms involved in this oxidation process by identifying molecular structures and chemical products formed during this exposure to oxidative Earth environment. The experimental method is described below.
The analogs of Exo-Earth or Super Exo-Earth aerosols were produced by a cold RF plasma fed by a mixture N2/CH4 in volume proportion 95/5. The solid matter was then exposed to ambient air during several months and extracted in methanol, acetonitrile, and water. The dissolved fraction was finally derivatized using MTBSTFA before being analyzed by GC-MS.