Formation of NH3 and CH2NH in Titan's upper atmosphere

Abstract

The large abundance of NH₃ in Titan's upper atmosphere is a consequence of coupled ion and neutral chemistry. The density of NH₃ is inferred from the measured abundance of NH₄⁺. NH₃ is produced primarily through reaction of NH₂ with H₂CN, a process neglected in previous models. NH₂ is produced by several reactions including electron recombination of CH₂NH₂⁺. The density of CH₂NH₂⁺ is closely linked to the density of CH₂NH through proton exchange reactions and recombination. CH₂NH is produced by reaction of N(²D) and NH with ambient hydrocarbons. Thus, production of NH₃ is the result of a chain of reactions involving non-nitrile functional groups and the large density of NH₃ implies large densities for these associated molecules. This suggests that amine and imine functional groups may be incorporated as well in other, more complex organic molecules.