JPL/Mars question

[Woody1458]

I was just watching a speech from JPL director Charles Elachi . And he was explaining why the rover lasted so much longer then anyone expected. Turns out that "dust devils" would run over the machine periodically cleaning the dust off the solar panels solving the problem which lead JPL to originally predict it's famous 90 estimation. My question is, with such a low atmospheric pressure on mars, how can a dust devil be obtained? I'm just guess on the dynamics of these miniature tornado but is it not that winds in two separate direction give dust particles enough centripetal force for them to begin to rotate? Where do these winds originate and how, if they exists, can they be strong enough to maintain a vortex.

Note to Mods: I couldn't find an appropriate section to put this question, it seemed Off-topic was only for social things and every other technical section was FIRST based.