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Latitudinal Variations of SO2 Above the Clouds of Venus Using SPICAV-UV/Venus Express

Emmanuel Marcq 1 Jean-Loup Bertaux 1 Franck Montmessin 1 Denis Belyaev 1, 2 Anna Fedorova 2 
LATMOS - Laboratoire Atmosphères, Milieux, Observations Spatiales
Abstract : Sulphur dioxide (SO2) is a key trace species in the atmosphere of Venus since it is thought to have been outgassed recently in Venus' history during the past 10 million years and thus linked to a possible geological acivity of the surface. Measurements in the UV range, just above the upper cloud deck, have been acquired for the past 30 years. These measurements show a long-term as well as a latitudinal variability. Our study is using data from the UV channel of the SPICAV spectrometer onboard Venus Express (170-320 nm, R 200). Although primarily designed for occultation studies, we used it in nadir mode, analyzing the solar radiation reflected and scattered by the upper atmosphere and cloud deck in a search for the spectral signatures of SO2 and SO, using synthetic reflectance ratios coming from radiative transfer models (SHDOM, SPSDISORT, Monte-Carlo) to fit our data. As a result, we have been able to detect an enhancement of SO2 at lower latitudes relative to the northern higher latitudes (70°N and above). The exact figure is highly dependent on our cloud parameterization, but is close to 100 ppb at the nominal cloud top level (70 km). Some constraints on the imaginary index of the unknown UV absorber could also be derived from our analysis past 300 nm.
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Submitted on : Monday, February 6, 2012 - 4:23:28 PM
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Emmanuel Marcq, Jean-Loup Bertaux, Franck Montmessin, Denis Belyaev, Anna Fedorova. Latitudinal Variations of SO2 Above the Clouds of Venus Using SPICAV-UV/Venus Express. 41st Annual Meeting of the Division for Planetary Sciences (DPS), Oct 2009, Puerto Rico, United States. ⟨hal-00667016⟩



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