At the Gusev area and Spirit rover I can remember a couple of rocks clearly eroded from underneath with a electro-chemical process almost certainly, the ground surface remaining level(not a wind evacuation appearance), and, a couple other small hollows at the front and underside of other rocks, but they seemed to have a problem of loss of substance from the rock mass filling the void caused by the wind as fast as the wind could carry the particles to the downwind side of the rock.
The example which might show the forward movement would be difficult to view if the idea is to know of a slight forward absolute motion during erosion of a ground plane soil level. A front stone with a mass of downwind stones blocking a wind speed might have the described effect, and that seems to be the discussion in the popular reportage, I haven't heard of any examples supplied as yet.
I did see a very small ovoid shaped well rounded particle at Eagle crater which was eroded to a finely smoothed shape, sitting within a shallow solid layer hollow, giving the appearance of the particle spinning an erosion hollow into the layered fairly solid surface. The two items seemed to have been related over geologic time, despite the changing of the weather and wind. No farward motion, but a steady erosion downward perhaps. It could have been a suggestive co-incidence as well.
I wonder if the wind chill and frost could produce the forward push, if the wind and sun were common at a low incidence angle, as in the polar regions. In the polar regions on Mars some of the layered terrain lacework is clearly more eroded on the sunlit sides, giving a downslope from elevated ice layers which could serve to move items into wind sourced from the sunlit side. It would require the erosion periods to have the same wind direction in a stable pattern during seasons and possibly even over geologic time. The wind arriving with the sunlight angle, erosion then not of the wind, but of a sun powered process.
Here is one of the most current HiRISE images, as a small sub-image supplied on the main image page.
This shows a slide of dune material, where the slide gas not darkened, but mixed the dark surface materials with the dune particles during the slide, giving a fan and a secodary slide from the first, which is at the lower elevation a little dark . The HiRISE suggestion is of a sublimating CO2 frost/ice allowing the slide, but here it seems to me that the buildup of the frost/ice has caused a simple landslide with the frost giving the particles a better rolling capability, with the frost retained along the dune surface, rather than sublinating.
The motion was gravity controlled and was a classic down the dune steeper side, but the area seems to show a varied wind directionality and cause which gives the appearance of possibly blowing 'backwards' towards the slide. face. That wind motion would give a slight forward pressure or a deflection lift to the steep dune face where the slide occured.
If you look at the upper right corner of the sub-image where the very shaped and eroded solid layers are patterned as 'yardangs', the slightly brighter sweeps of frost have followed the wind blowing, causing a series of darker lanes between the frost on the low elevation surfaces. The frost is depositioned there selectively by terrain wind micro-patterns.
Possibly this shows some slight support to the idea of forward wind slides as caused by the available steep slope and gravity. The areas I thought should be greater in current wind pressure, seem to have reduced the frost, with either the sublimation, or wind force as the cause of the slides. Reversal of winds may be a weather controlled slide process due to temperature, but the overall image at lessened detail showed non directional frost to my view.
I'll finish downloading the larger image, a JP2.
I'll look for the wind at small scale detailed areas for any other movement related. Would the frost removed in lanes like these be the actual cause of the slide, perhaps? It looks to me that the wind or water shaped these teardrop shapes, and there are linear benched levels along the far right side of the layered solid surface at the marked corner.
PSP_010546_2615. A nice image of darkened dune surfaces, which show no darkened sliding other than dark material mixing to an intermediate tonality. The darkening apperars to be a chemical process in situ.
Have we seen an example here, of a 'cultured' or 'slanted' supporting example of forward wind rolling? We really can't see wind comning from the dark and more probable direction. Someday they'll possibly use radar for the detailed wind tracking.
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As I've mentioned on other topics, you have to click several ever larger images to get the final full size. It should fill a 1050x1650 pixel screen and show the slightly brighter wind driven frost with the darker lanes between them.