HR: 1330h
AN: A12A-0066 INVITED     [PDF]
TI: Photochemistry of the Giant Planets
AU: * Moses, J I
EM: moses@lpi.usra.edu
AF: Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston, TX 77058-1113 United States
AB: Photochemistry in the hydrogen-dominated atmospheres of Jupiter, Saturn, Uranus, and Neptune is interesting and complex despite the large heliocentric distances involved. Methane photochemistry dominates in the stratospheres of the giant planets; other "parent" molecules like H2O, NH3, and H2S are trapped in condensed phases and are confined to the troposphere. Methane photolysis initiates the production of complex hydrocarbons like C2H6, C2H2, C2H4, CH3C2H, C4H2, C6H6, and CH3 -- all of which have been detected on Jupiter and Saturn, and some of which have been detected on Uranus and Neptune. The photochemistry of ammonia and phosphine are coupled in the tropospheres of Jupiter and Saturn. Predicted products of this interaction include N2, N2H4, P4, P2H4, NH2PH2, with much lesser amounts of HCP, HCN, other nitriles like HC3N, CH3CN, and C2H3CN, and complex organo-nitrogen compounds like acetaldazine. None of these species have been definitively detected on the giant planets (except for HCN on Neptune and Jupiter). Water resides too deep in the tropospheres of the giant planets to interact with ultraviolet photons; however, oxygen is introduced to the upper atmospheres of the giant planets through external interaction with comets, interplanetary dust particles, and ring/satellite debris. The endproducts of the stratospheric oxygen photochemistry are CO, H2O, and CO2, with lesser amounts of H2CO, CH3OH, and CH3CHO. The possible tropospheric photochemistry of H2S on the giant planets is poorly understood due to a dearth of appropriate rate-coefficient information. Recent advances in our understanding of atmospheric photochemistry of giant planets, including that of extrasolar giant planets, will be reviewed.
DE: 0317 Chemical kinetic and photochemical properties
DE: 0343 Planetary atmospheres (5405, 5407, 5409, 5704, 5705, 5707)
DE: 5704 Atmospheres--composition and chemistry
DE: 5709 Composition
DE: 6207 Comparative planetology
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting