That is pretty cool, I can't imagine the wind speed were that high. However, it did leave a track on the ground. But if I know my martian surfaces, the surface is not hard, very sandy. Only one can guess
The dust devils that the Spirit rover has been imaging appear smaller, nearer the average sizes of Earth dust devils (on the order of 10 m or so). This leads me to believe that there is large range of scales of dust devils on Mars, and the satellites see the very biggest ones. Now that we have rovers on Mars, they are seeing some of the smaller ones.
I did some undergraduate research on dust devils, and I sometimes chase them . Been inside a few
I cant believe someone didnt think of a wiper blade or tilting mechanism to clean the solar panels, I remember hearing a scientist say one of the factors that would lead to the demise of the rovers was dust collected on the panels.
Keeping on topic, barely, I hope the whirlwinds any larger dont throw debris (rocks, hailstones) at the panels, then theyre done! 15 months is a great job though!!