What you mean "natural?" It's OBVIOUSLY an artifact.

More and more ammazing beauty

...okay, THAT is flat-out cool as hell!!! How did you define your colorization scheme? That middle stripe of orange in each of the dune valleys is quite striking!

Aren't they the dune peaks? If they aren't then something truly odd is going on with all those boulders on the tops of the dunes...

Yeah, you must be right. It's hard (for me, anyhow) to gauge perspective in this image.

My guess--Orange stripes are dune peaks, rocks at valley bottom--like dunes on bedrock around Opportunity.

No the dunes are very dark and the bedrock is light and strewn with boulders. Really plays games with your shadow perception.

It actually helps - as is often the case with HiRISE images, I think - if you look at the black and white version first. Then it is clear that the boulders are "filling in the gaps" between the dunes...



(very cool dust ripple filled crater between the dunes there, don't you think?)

The bright "stripe" along the top of the dunes appears to be the dunes' actual peak..?

Very easy: copy-paste from a link @jpl

The orange stripe in the color image is actually in the slope of the dune face. It's probably just a different grain size than the surrounding material, as that's typically what HiRISE colors indicate. The dune crest is the smooth-looking dark portion in the grayscale image.

here is a quick try at a single-image-SFS-DEM from the JPG above:






Note that in this case the algorithm in its current implementation does have troubles with the extreme albedo differences between the blackish dunes and the light colored rock (i.e variations in brightness that are not caused by illumination only) which causes distortions in the low frequency variations ...

Nevertheless the visual impression turned out quite interesting so I decided to post it anyway (and the vista does give a general idea on how this scene might look like when seen from the ground )

In the CTX image P21_009058_1349_XI_45S255W
I saw this strange feature. What is this?

Freaky-looking thing. The whole area looks like either an outflow plain or perhaps even a dust-covered glacier. Perhaps an oblique crater pair that was subsequently overrun by an ice or water flow?

I'd go with a deposit leftover from some sorta glacier-thingy. Almsost seems like there is a trail behind it. There's a lot of areas nearby that look like they slumped out.

Nice catch; that is truly weird. Based on other nearby features I'd say it was the remains of a multiple crater rim but it looks truly odd. Note the image is not HiRISE but CTX! I checked HiWish and there is no HiRISE image over the feature. I won't preempt your find; you should go to HiWISH and ask for a higher resolution view!