DPS 2001 meeting, November 2001
Session 34. Mars Atmosphere II: Clouds and Dust
Oral, Chairs: M. Wolff, A. Colaprete, Thursday, November 29, 2001, 4:40-6:10pm, Regency E

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[34.08] Martian Airborne Dust: a Bimodal Size Distribution?

F. Montmessin, P. Rannou, M. Cabane (Service d'Aeronomie - IPSL)

We study the light scattered by hazes at Martian limb using a direct method combining a microphysics and a photometric simulation of the Martian atmosphere. We are able to reproduce vertical profiles of light intensity as those deduced from limb observations of the Viking orbiter at two visible wavelengths.

We investigate the results consistency with several published airborne dust models. As a major conclusion, the currently admitted dust distributions are unable to satisfy constraints provided by the Viking observations. Including an additional mode composed of small particles to a classical size spectrum allows to match both vertical and color behavior of the Martian dust hazes. This hypothesis is largely supported by the observations of soil-derived aerosols in terrestrial desert regions. Moreover, this consideration should help to explain the canonical dust visible to infrared opacity ratio.

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