Vertical and meridional distribution of ethane, acetylene and propane in Saturn's stratosphere from CIRS/Cassini limb observations

摘要: Abstract Measuring the spatial distribution of chemical compounds in Saturn’s stratosphere is critical to better understand planet’s photochemistry and dynamics. Here we present an analysis infrared spectra range 600–1400 cm−1 acquired limb geometry by Cassini spacecraft between March 2005 January 2008. We first determine vertical temperature profiles from 3 0.01 hPa, at latitudes ranging 70°N 80°S. infer a similar meridional gradient 1–2 hPa as recent previous studies [Fletcher, L.N., Irwin, P.G.J., Teanby, N.A., Orton, G.S., Parrish, P.D., de Kok, R., Howett, C., Calcutt, S.B., Bowles, N., Taylor, F.W., 2007. Icarus 189, 457–478; C.J.A., Simon-Miller, A., Fletcher, 190, 556–572]. then retrieve C 2 H 6 0.01 hPa 8 around 1 hPa. At 1 hPa, variation found follow yearly averaged solar insolation, except for strong equatorial mole fraction × 10 - 7 , nearly two times higher than expected. This enhancement abundance can be explained descent hydrocarbon-rich air, with wind speed equator 0.25 ± 0.1  mm/s 1 hPa 0.4 0.15 0.1 hPa. The ethane relatively uniform only moderate 25% increase 35°S Propane north south factor 1.9, suggesting that its lifetime may shorter year high altitudes (1 Pa),  and  abundances depart significantly photochemical model predictions Moses Greathouse [Moses, J.I., Greathouse, T.K., 2005. J. Geophys. Res. 110, 9007], southern (62, 70 80°S) near equator. observed abundances are strongly depleted 20–40°S region enhanced 20–30°N region, latter coinciding ring’s shadow. favor dynamical explanation these anomalies.