Interaction dust–plasma in Titan's ionosphere: Feedbacks on the gas phase composition - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles (Review Article) Icarus Year : 2023

Interaction dust–plasma in Titan's ionosphere: Feedbacks on the gas phase composition


Titan's organic aerosols are formed and spend some time in the ionosphere, an atmospheric layer ionized by solar VUV photons and energetic particles coming from the magnetosphere of Saturn, forming a natural N2-CH4-H2 plasma. Previous works showed some chemical evolution processes: VUV photons slightly alter the aerosols nitrile bands, hydrogen atoms tend to hydrogenate their surface and carbon-containing species participate to the growth of the aerosols. This work investigates the effect of the other plasma species, neglected until now, namely the N2-H2 derived ions, radicals and electronic or vibrational excited states. Industrial plasmas often use N2-H2 discharges to form ammonia-based fertilizers, for metal nitriding, and to erode organic surfaces. Consequently, these are likely to affect Titan's organic aerosols. We therefore developed the THETIS experiment (for Tholin Evolution in Titan's Ionosphere Simulation) to study the interactions between analogues of Titan's aerosols (tholins) and the erosive N2-H2 plasma species found in Titan's ionosphere. Following a first paper on the investigation of the evolution of the solid phase by Scanning Electron Microscopy and IR transmission spectroscopy (Chatain et al., 2020a), this second paper focuses on evolution of the gas phase composition, studied by neutral and ion mass spectrometry. In the presented experiments, newly formed HCN, NH3-CN and C2N2 are extracted in quantity from the tholins as well as some other carbon-containing species and their derived ions. On the other hand, the production of ammonia strongly decreases, probably because the H, NH and N radicals are rather used for the production of HCN at the surface of tholins. Heterogeneous processes are suggested based on the experimental observations: chemical processes induced by radicals at the surface would modify and weaken the tholin structure, while ion sputtering would desorb small molecules and highly unsaturated ions. The effect of plasma erosion on aerosols in Titan's ionosphere could therefore lead to the formation of Ctriple bondN bonds in the aerosol structure, as well as the production of HCN or R-CN species in the gas phase.
Fichier principal
Vignette du fichier
2303.00062.pdf (2.94 Mo) Télécharger le fichier
Origin : Files produced by the author(s)

Dates and versions

insu-04014563 , version 1 (04-03-2023)



Audrey Chatain, Nathalie Carrasco, Ludovic Vettier, Olivier Guaitella. Interaction dust–plasma in Titan's ionosphere: Feedbacks on the gas phase composition. Icarus, 2023, 396 (May), pp.115502. ⟨10.1016/j.icarus.2023.115502⟩. ⟨insu-04014563⟩
21 View
21 Download



Gmail Facebook X LinkedIn More