[Previous] | [Session 48] | [Next]
F. Ferri (ESTEC-ESA Solar System Division), P. H. Smith, M. Lemmon (Lunar and Planetary Laboratory, University of Arizona), N. O. Rennó (Atmospheric Sciences Department, University of Arizona, Tucson)
Dust devils have been observed on Mars by the Viking Orbiters and Landers [Ryan and Lucich, 1983; Thomas and Gierash, 1985], by the Mars Pathfinder [Schofield et al., 1997; Metzger et al., 1999] and more recently by the Mars Global Surveyor. Dust devils are low-pressure, warm-core vortices that form at the bottom of convective plumes and loft dust from the surface; on Earth they are frequently observed in hot arid regions. They move with the speed of the ambient wind and slope in the wind shear direction. On Mars, they might play an important role in the maintenance of the atmospheric dust. In the Pathfinder data, dust devils have been detected as dust plumes in the IMP images and as convective vortices in the ASI/MET temperature, pressure and wind data. The size and location of the dust devils observed in the IMP images have been estimated based on assumptions about the ambient wind. The obtained results are in good agreement with the Pathfinder ASI/MET data and observations by the Viking 1 orbiter. A simple thermodynamic theory for dust devils [Rennó et al., 1998;1999] has been used to compute the intensity and some physical parameters of the Martian dust devils. Moreover, their capability of lofting dust high into the atmosphere has been investigated on the basis of Pathfinder’s observations. It is concluded that Martian dust devils can provide a pumping rate comparable to the dust settling rate derived from the optical obscuration of the solar panels of the Pathfinder rover [Rover team, 1997]. Therefore, they might be responsible for the maintenance of the dust normally observed in the Martian atmosphere.