Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express: Carbon dioxide measurements at the Venus terminator

A. Mahieux (1) , A. Vandaele (1) , S. Robert (1) , V. Wilquet (1) , R. Drummond (1) , Franck Montmessin (2, 3) , Jean-Loup Bertaux (2, 3)

1 BIRA-IASB - Belgian Institute for Space Aeronomy / Institut d'Aéronomie Spatiale de Belgique
2 PLANETO - LATMOS
3 IPSL (FR_636) - Institut Pierre-Simon-Laplace

SOIR is a high resolution spectrometer flying on board the ESA Venus Express mission. It performs solar occultations of the Venus high atmosphere, and so defines unique vertical profiles of many of the Venus key species. In this paper, we focus on the Venus main constituent, carbon dioxide. We explain how the temperature, the total density and the total pressure are derived from the observed CO2 density vertical profiles. A striking permanent temperature minimum at 125 km is observed. The dataset is processed in order to obtain a Venus Atmosphere from SOIR measurements at the Terminator (VAST) compilation for different latitude regions and extending from 70 up to 170 km in altitude. The results are compared to many literature results obtained from ground-based observations, previous missions, and the Venus Express mission. The homopause altitude is also determined.

Mots clés: Venus; Composition; Model; Planetary atmosphere

Domaines: Planétologie et astrophysique de la terre [astro-ph.EP]; Physique Atmosphérique et Océanique [physics.ao-ph]

A. Mahieux, A. Vandaele, S. Robert, V. Wilquet, R. Drummond, et al.. Densities and temperatures in the Venus mesosphere and lower thermosphere retrieved from SOIR on board Venus Express: Carbon dioxide measurements at the Venus terminator. Journal of Geophysical Research. Planets, 2012, 117 (E7), pp.E07001. ⟨10.1029/2012JE004058⟩. ⟨hal-00705633⟩