Haskin Ridge, The Eastern Route Down to the Basin Options

[CosmicRocker]

Possibly, it seems very likely that it is a dust shadow caused by windborne dust dropping out of the atmosphere as the prevailing wind passes over the hill top and slows down as it expands  on the lee side.  ...

That's what I think the origin of the areas of dark sand is, too. I once tried to explain the process, but you found better and fewer words to describe it quite nicely.

[Nix]

Discussion on colorizing the images continued here;

Methods for colorization of Pancam images

Nico

[atomoid]

That's what I think the origin of the areas of dark sand is, too.  I once tried to explain the process, but you found better and fewer words to describe it quite nicely. 

it certainly makes sense, since these deposits seems to correspond to wind shadow areas, but its still sort of an enigma: Why is it particularly only the dark dust that collects here?

Is the dark dust lighter (and hence collects there in thick deposits where it cant get airborne again, yet the less-dark (but heavier) dust does not collect here, perhaps drops out earlier)?

...or is the dark dust heavier and so it builds up whereas the lighter dust blows away, perhaps hurried along by the thermal aspects (spawning updrafts?) of the darker dusts that it cant quite settle upon in the windy conditions whereby it is able to become airborne in the first place. If it were heavier it must have been laid down under some very strong wind conditions much like river sandbar deposits during a flood, perhaps relatively long ago, and is able in these areas to keep itself clean this way (which would imply these are tip-of-the-sandberg dark sands and also exist in large deposits under many other lighter-covered areas where the winds dont keep them clean this way, or somehow)...

Note also that the dark dust is only 'dark' in certain wavelengths (and maybe its not basaltic)...
...there is probably an easier answer to be found by looking at other wind-shadow features at different scales.

[RonJones]

I wonder what Steve S. has been up to. He hasn't posted an update on the Cornell Athena rover web site for 5 weeks.

I suspect a NASA video news conference is being planned for sometime in early Jan. to mark 2 years on Mars for the rovers.

Ron Jones