It seems like the wind swept, hot/cold environment has broken down much of the rocks and carry these beach like granules (sediment?) all over the surface and the bedrock. The lighter bedrock seems to be revealed at points in other images. The lesser gravity of mars increases the depth because these granules and bigger rocks are not pulled down by weight as they would be on earth.

This same gravity disparity is what has accentuated the rover tracks - making these fine granules look like wet sand. There is simply less pull on them and it leaves the impression almost exactly as it was formed. When the winds subside the surface takes the consistency somewhat of light ash fallen after a fire.

It seems very dry. The movement of the granules is smooth and does not appear to bind. More like the eroded rock sand high upon a beach above the reach of the waves.

Earlier someone commented about the reflective surface where the airbags struck the san versus the seeming less reflective tire tracks. I think these images clearly show reflection and lightening of the rocks is due to compacting. Martian gravity simply doesn't pack things down much. The airbag impacts probably placed the most pressure on the surface and because it is thick and fine it flattens very smoothly and this compacting increases any surface areas reflectivity of light.

The formation of these consistent granules is the mystery. Their spherical nature indicates forming in a suspended body equally surrounded by erosive forces. Wind alone, I tend to think, would produce finer particles and actual dust. The spherical pebbles, and the stones with holes indicate the likelihood of either igneous origin of this material, sedimentary or both.

How is it either are still apparent on the surface after such significant amount of presumed time has elapsed? Here I think we may find our solution in the intensity of sunlight that reaches mars. Solar radiation actually strips molecules of their binding forces over time, allowing for a very fine dust to be created during the persistant erosion process. Heat alone is not as significant to this breakdown as is this solar radiation. I think that we will/do see a finer breakdown of these particulates on mercury, venus, earth and the moon. Further out into the solar system, such as Europa and Jupiter's other moons I suspect we will find ever larger rockier surfaces in part due to this lack of radiation and subsequent breakdown.

It is not that mars has no fine dust - it does. This just means that mars is not earthlike in its production of dust and that I suspect it takes much longer to create it in the same quantities. This then makes these either sedimentary or igneous granules probably seem fresher than they really are.

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