So after 20 pages of discussion, thank god we appear to have an official answer.

That's his current take - not the official definative answer.

Doug

Opportunity was futzing around in that spot for several sols with its IDD. The grains there are not as
cohesive, perhaps due to a lack of dust, so impressions don't take. All the pressing and brushing of
the IDD caused a brazil nut effect, bringing additional berries to the surface. Lets also assume an
optimum depth of loose material over bedrock for this effect, whatever depth that is...

Or.... the finger of berryless sand that Opportunity was investigating
was not a flat surface feature, but a tiny ridge of windblown material
extending out from the tip of the rock. Opportunity's investigations
flattened out this ridge exposing berries that were within or below
it. Again, due to its lack of dust and fine particles, the sand flows
as a liquid: marks and impressions are not easily retained.

I'm happy to hear that Jim's preliminary assessment is favorable to cleaning, but the real excitement tosol seems to be the remarkable change between sol 1145 and sol 1148 MIs. That is an unexpected change. That little ripple that was on the lee side of the rock is now mostly gone. There is a dent in the area from an instrument that might have disturbed the soil, but I also see dust being removed from other areas well away from that disturbance. Could the proximity of the instrument package, IDD, and rover have altered the local wind vectors here, causing that fine stuff to blow away?

This was bewildering me tonight until a friend sent me a link to http://www.flickr.com/photo_zoom.gne?id=466694284&size=o

That's quite a clincher. It seems pretty clear that it is windy here. I think Oppy should configure it's movable parts to create the maximum wind turbulence toward its solar panels.

That's a great show of the appearance of previously hidden berries, but
I don't think it shows any results of short term wind action. I think the
"dust" you see in the color image is really the result of lower contrast
and lack of focus. In the black and white image the contrast and focus
jump and make it look like dust has cleared. I look around but do not
see the appearence of any previously unseen berries anywhere but at
the sandy spot the rover was looking at next to the rock.

I think the IDD was placed there specifically to get a look at built up
windblown material with no berries and the activity of the IDD caused
the sand to slide or shimmy away revealing the berries.

Before and after...

Pile o'rocks...



...meteorite, you reckon? If so I'd love to get stuck into it... what a great strewnfield to study and gather specimens from!

sol 1144-1149 L247:



Maybe Oppy should stick around here for a while.

And here is the L234567 color version of my animation CosmicRocker's friend sent him.

Horton, that flicker gif of Alicante is exactly what I wished I could do! Thanks for that!

Rocker, what about the flicker gif convinces you it's windy? We do know it's windy, recall the light dust blowing out of the rover tracks. But it seems quite a stretch to say wind exposed these berries.

OK, now I see berries moving in the wind.
I see a group of small berries just off the 10 o'cock position of the sundial ball.
I see several large berries along the very top, right of center, in the image.
I see others moving here and there, all to the right, and down a little.
I can't think of anything but wind moving them.
But why no "cleaning event"?

GREAT WORK HORTON!

Holy smokes...so what's going on with the power output?

Jim Bell's comments yesterday were accompanied by colour pancam's and an MI that seemed to me to indicate that the dark streaks were areas where cleaning effects predominate resulting in a surface layer that is more densely populated than average with blueberries that are themselves very clean. He was very specific about the terms "swept clean" and "polished surface's" when describing the areas but as Doug says these were just comments and not definitive rulings. That said his comments seemed to me to be a strong endorsement of the hypothesis that the dark streaks at Victoria's northern edge are caused by cleaning not deposition. He didn't comment on other areas that seem to be composed of dark materials that have been mentioned in this thread by the way.

I think the nature of the annulus (a very flat smooth surface with a relatively durable surface layer with lots of blueberries) is a major factor here. Whatever long term process that has created it must be compatible with the short term effects - if deposition of darker dust\sand scale material is the dominant cause then it should dominate the entire area eventually as the crater has changed shape and eroded back. What we actually see on the ground is the effect of MY\GY of very gradual erosion of both the crater and the original ejecta debris field that has lead to this very flat blueberry dominated crust where finer materials (dust\sand scale) are preferentially removed by the wind.

The animation of the wind action between 1144 & 1149 is dramatic. Not to disregard Jim Bell's remarks... If the wind is this strong here, what's it like at the mouth of the bay? It appears to be capable of moving berries. Shouldn't it be moving the dark matterial in the bays and below the cliffs? And if that's the case, is there any way it would not end up in the streak area?

It has crossed my mind that the polishing of the berries might be a contributor to the darkening...

Yes it should, if there is any "dark material" there to begin with. Otherwise
it will move all the sand -- light and dark -- and completely clear away the dust.
Still, I don't see any unique "dark material" in any of the latest images.