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[37.20] Observation of CO2 fluorescent emission at the limb of Mars by OMEGA/Mars Express

P. Drossart, M. Combes, T. Encrenaz, R. Melchiorri, T. Fouchet (Paris Obs.), F. Forget (LMD, Paris), N. Ignatiev (IKI, Moscow), J.P. Bibring, Y. Langevin (IAS, Orsay), OMEGA Team

Observations in limb geometry with the imaging spectrometer OMEGA on board Mars Express (Bibring et al, Nature, 2004) at 4.3~\mum have been obtained at various longitudes and solar zenith angle between January and July 2004. They present prominent off-limb emission in CO₂, which correspond to fluorescent emission of solar light in non-LTE regime. A peak emission is observed at ~90 km. Emission of CO₂ fundamental is observed as well as isotopic ¹³CO₂. Spatial/spectral scans allow us to observe the vertical structure of the atmosphere at a kilometric vertical scale. CO fluorescence is also observed, and vertically resolved, with peak altitude at ~50km. Variation in intensity and in altitude of the peak emission is observed from orbit to orbit, which seem to indicate atmospheric variability in the upper atmosphere, possibly related to atmospheric structure. Observations in limb geometry will continue with Mars Express to cover other latitude and longitude during the nominal mission. In addition to CO and CO₂ emission, O₂ dayglow emission is also detected in the Northern regions, with a strong latitudinal variation.

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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.