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[54.08] A Preliminary Work to \emph{Venus Express} : Near IR Spectro-Imagery of the Lower Atmosphere .

E. Marcq, T. Encrenaz, B. Bézard (LESIA - Obs. de Paris), M. Birlan (LESIA/IMCCE - Obs. de Paris)

Near-infrared spectroscopy of Venus' nightside provides a unique means of probing the lower atmosphere of the planet. Shortward of 2.4 microns, thermal emission from beneath the clouds can be detected in narrow atmospheric windows between the strong CO₂ and H₂O bands. We observed the night side of Venus in the K-band at the NASA/IRTF using the SpeX spectro-imager, during two Venusian quadratures in Feb. 2003 and Aug. 2004. Our goal is to map the abundances of the gaseous absorbers present in the 2.3-\mum window in order to study the dynamics of the Venusian atmosphere below the cloud layers, and to search for possible sources of sulphur-bearing gases. Latitudinal variations of CO and OCS in the 25-40 km region have been derived and a similar study on H₂O is in progress. The CO abundance shows an increase of about 15% from the equatorial region to higher latitudes. Wherever the S/N ratio is good enough, there appears to be an anticorrelation of the CO and OCS distributions.

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Bulletin of the American Astronomical Society, 37 #3
© 2004. The American Astronomical Soceity.