Formation and photochemistry of Methylamine in Jupiter's atmosphere

Abstract

The formation of methylamine (CH 3NH 2) in the upper troposphere and lower stratosphere of Jupiter is investigated. Translationally hot hydrogen atoms are produced in the photolysis of ammonia, phosphine, and acetylene which react with methane to produce methyl (CH 3) radicals; the latter recombine with NH 2 to form CH 3NH 2. Also, methane is catalytically dissociated to CH 3 + H by the species C 2 and C 2H produced in the photolysis of acetylene. It is shown that the combined production of CH 3NH 2 and subsequent photolysis to HCN is unlikely to account for the HCN observed near Jupiter's tropopause. Recombination of NH 2 and C 2H 5N followed by photolysis to HCN is the preferred path. Production of C 2H 6 by these two processes is negligible in comparison to the downward flux of C 2H 6 from the Lyman α photolysis region of CH 4. An upper limit column density on CH 3PH 2 is estimated to be ∼10 13 cm −2 as compared to 10 15 cm −2 for CH 3NH 2. Hot H atoms account for a negligible fraction of the total ortho-para conversion by the reaction H + H 2