Organic chemistry on Titan

Journal Article · Thu Nov 01 04:00:00 EST 1979 · Rev. Geophys. Space Phys.; (United States)

DOI:https://doi.org/10.1029/RG017i008p01923· OSTI ID:5756983

Chang, S; Scattergood, T; Aronowitz, S; Flores, J

Observations of nonequilibrium phenomena on the Saturn satellite Titan indicate the occurrence of organic chemical evolution. Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are assessed. Experimental results and theoretical modeling studies suggest that the organic chemistry of the satellite is dominated by two atmospheric processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH/sub 4/ in the upper atmosphere can account for the presence of C/sub 2/ hydrocarbons. Reactions initiated in various levels of the atmosphere by cosmic ray, Saturn 'wind,' and solar wind particle bombardment of a CH/sub 4/-N/sub 2/ atmospheric mixture can account for the ultraviolet-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C/sub 2/ hydrocarbons. In the lower atmosphere, photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH/sub 3/ to exist. Hot H atom reactions initiated by photodissociation of NH/sub 3/ can couple the chemical reactions of NH/sub 3/ and CH/sub 4/; if 0.1% of the incident ultraviolet light from 1600 to 2270 A reaches the lower atmosphere, these reactions will be capable of producing organic matter at a rate comparable to or higher than that resulting from particle-initiated reactions. Electric discharges are highly improbable on Titan; if they occurred at all, they would be restricted to the lower atmosphere and clouds. Their yield of organic matter might approach that of hot H atom reactions if the conversion of solar to electrical discharge energy on Titan was as efficient as that on earth. These assessment indicate that future missions to Titan should include organic chemical analyses of its atmosphere and surface among the prime science objectives.

• Research Organization: Extratterestrial Research Division, NASA Ames Research Center, Moffett Field, California 94035
• OSTI ID: 5756983
• Journal Information: Rev. Geophys. Space Phys.; (United States), Journal Name: Rev. Geophys. Space Phys.; (United States) Journal Issue: 8 Vol. 17:8; ISSN RGPSB
• Country of Publication: United States
• Language: English

Related Subjects

640107* -- Astrophysics & Cosmology-- Planetary Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AMMONIA
ATMOSPHERES
COLLISIONS
DUSTS
EARTH ATMOSPHERE
ELECTRIC DISCHARGES
ELECTROMAGNETIC RADIATION
HYDRIDES
HYDROCARBONS
HYDROGEN COMPOUNDS
LIGHTNING
MOLECULE COLLISIONS
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
ORGANIC COMPOUNDS
PLANETARY ATMOSPHERES
PLANETS
RADIATIONS
SATELLITES
SATURN PLANET
STRATOSPHERE
ULTRAVIOLET RADIATION