Dust and cloud detection at the Mars limb with UV scattered sunlight with SPICAM

Pascal Rannou (1) , Séverine Perrier (1) , Jean-Loup Bertaux (1) , Franck Montmessin (1) , Oleg Korablev (2) , Aurélie Reberac (1)

1 SA - Service d'aéronomie
2 IKI - Space Research Institute of the Russian Academy of Sciences

The UV detector of Spectroscopy for the Investigation of the Characteristics of the Atmosphere of Mars (SPICAM) on board Mars Express has measured several profiles of light scattered at the limb of Mars. In this paper we present 33 profiles taken between January 2004 and August 2005. Scattering of UV light at the limb of Mars is due to the molecules of the atmosphere, dust particles, and sometimes cloud particles which appear as detached layers above the extended dust layer. We have used a radiative transfer model to retrieve the haze and cloud properties. Rough estimate of the particle size shows that both cloud particles and dust particles above 20 km are in the range 10 to 100 nm. Such particles are much smaller than micron-sized dust particles previously observed in the lower atmosphere, generally from landers. Gravitational segregation is thought to be responsible for these differences in particle size between low and high atmosphere.

Mots clés: limb scattering; ultraviolet; cloud; photometry; mars; dust

Domaines: Planète et Univers [physics]

Pascal Rannou, Séverine Perrier, Jean-Loup Bertaux, Franck Montmessin, Oleg Korablev, et al.. Dust and cloud detection at the Mars limb with UV scattered sunlight with SPICAM. Journal of Geophysical Research. Planets, 2006, 111, pp.E09S10. ⟨10.1029/2006JE002693⟩. ⟨hal-00102988⟩