What has kind of bugged me about the design of the rovers is, if they knew the environment was dusty, and that they're relying on the solar panels being relatively clean to provide optimal power... wouldn't you incorporate some kind of motorized brush, sorta like a windshield wiper, designed to keep at least a large amount of the surface area of the solar panels nice and clean (if not all of it)? The weight cost would only have to be what, 1-2 pounds (a small fraction of a percent of the rover's total weight)? And the power cost would be negligible compared to the potential gain in power received from more efficient panels. Seems like an oversight, but maybe for a good reason beyond my understanding.

Or another idea would be to do something like you see on TV cameras at outdoor events where it's raining, where they have a sheet of clear material over the lens that they can roll from one side to the other. You could have a loop of such material arranged like a tank tread around the top and bottom of the solar array, with a tiny motor to scroll it around as necessary, and a stationary brush on the backside to clean it as it scrolls by... that way, when the top surface gets too dusty, you run the "clean" side around from the bottom (over the brush to make sure it's as clean as possible) and the dirty side around to the bottom where the dust could fall off and anything left would eventually be brushed off when you cycle the screen the next time. Again, I think it could be done with fairly negligible weight and power hits. The only reason I could see to not do either of these things is simplicity, which I can definitely understand... operating millions of miles away, the fewer things you have to worry about breaking or failing, the better.