True enough
Indeed the whirlwinds do seem to leave barely perceptible tracks at ground level. Overhead viewing seems to enhance them greatly. Or maybe it's a contrast effect enhanced by the cameras and image processing.
What I'm getting to is a question about the nature of the surface materials that appear to be so dark, and whether they are similar to the materials forming the "Ultreya/El Dorado" deposit, and if this in turn is more or less similar to the vast sulfate/salts/blueberries deposits of Meridiani.
If so, wow.
If not, hmmm...
I think Nick is suggesting upthread that the deposits here are NOT similar to those of Meridiani, but instead consist of simple volcanic erosion products.
I'd sure like to know, though....