Dust Storms on Mars - Charge Tornadoes ?
Dust storms on Mars seem to have quite a different dynamic from any dust storm on earth.
The atmosphere is normally very cold and thin, almost too thin to carry the dust into giant storms that can spread to envelope the planet.
The surface features of the planet show little sign of mobile dune systems or surface features such as craters buried by drifts of dust.
There are what seem to be dune systems along the bottom of surface channels, but these never seem to build up into deep drifts.
Small craters appear crisp on this image.
I would suggest that the development of dust storms on Mars is driven by electrical activity, rather than by winds whipping up the dust into storms.
Simple petri dish experiments show how a layer of dust can be lifted off the surface by electrical charge and carried up as a dust tornado.
Once lifted off the surface the charged dust cloud then behaves as a dust atmosphere - a charge cloud atmosphere much thicker than the normal gaseousatmosphere.
This charged dust cloud can also absorb the sun's energy and throughcharge separation in turbulent dust cloud can develop into immense thunderstorms.These thunderstorms in turn generate more giant charge sheath tornadoesthat lift more dust from the surface.
Since the dust is being lifted by charge rather than winds, it can be lifted out of a shallow crater as easily as from an exposed crest - hencethe lack of any build-up of drifts.
It will be very interesting to see any narrow camera images of these dune systems after a major dust storm. Exactly the same image at yearly intervals will reveal a lot about the mechanics of charge driven weather on Mars.
A dust storm may continue to develop until the density of dust allows the insulation of charge to fall and the charge differential that drives thestorm collapses. This discharge may also be from the top of the dust storminto space.
Any probe arriving during a dust storm is in for a tough time, not from high winds, but from the electical discharges that may fry its electronics!
This information is copyright Peter Thomson 2001-2004