Triton:  stratospheric molecules and organic sediments.
Hydrocarbons and nitriles are produced in Triton's stratosphere by energetic electrons from Neptune's magnetosphere and other charged particle sources.  Laboratory plasma experiments reported here show a substantial yield of molecules from low pressure flows of 10(-3) CH4 in N2 appropriate to Triton if both CH4 and N2 are saturated at the surface.  An active magnetosphere similar to that of Uranus would result in a flux approximately 0.3 erg cm-2 s-1 of 0.1-1 MeV electrons in Triton's stratosphere; molecular production rates are then 10(6)-10(8) cm-2 s-1 for NH3, C2H2, HCN, and NCCN; tens of hundreds of gm cm-2 of these compounds per 10(9) yr (and lesser quantities of at least eight other molecules experimentally detected) would freeze to fine-grained white condensates in the lower stratosphere and sediment to the surface.  Along with dark/colored organic haze produced in the stratosphere and other heteropolymers produced at the surface, these condensates are subjects to redistribution by aeolian processes and may appear as lag deposits and/or sediment layers.  A simple eddy diffusion  model indicates abundances approximately 10(19) molec cm-2 for HCN and C2H2, and > 10(17) molec cm-2 for NCCN, CH3CCH, CH2CCH2, and CH3CN in the stratosphere; these and other organic molecules will be detectable by IRIS if the stratosphere is (as expected) heated through ultraviolet and visible light absorption by the haze.
Thompson
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WR
Laboratory for Planetary Studies, Cornell University, USA.
Singh
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SK
Khare
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BN
Sagan
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C
D001272:Atmosphere / Q000737:chemistry*; D004583:Electrons; D005118:Extraterrestrial Environment; D006838:Hydrocarbons / Q000032:analysis*; D006856:Hydrogen Cyanide / Q000032:analysis; D008697:Methane / Q000032:analysis; D008956:Models, Chemical; D018541:Neptune; D009570:Nitriles / Q000032:analysis*; D010777:Photochemistry; D013055:Spectrophotometry, Infrared / Q000379:methods; D014466:Ultraviolet Rays
D006838:Hydrocarbons; D009570:Nitriles; D006856:Hydrogen Cyanide; D008697:Methane