one of those long neglected issues:

How is dust produced on Mars?

Dust and sand are constantly invoked as if in explanation of this or that phenomenon, but we need to ask where the dust comes from. We shouldn't assume we know, especially not in Meridiani.

The spherical granules are interesting. They are likely not rocks. More likely they may be formed of the "dust" or whatever it is that is coating the surface. What could cause the dust to spontaneously form these tiny granules, granules which seem to disappear or disintegrate at the touch? How would they behave if moistened?

What would happen to moisture in this cold, dry near-vacuum? Is moisture involved in the spheroid production? Static electricity? Something else?

Those layers are intriguing too, as is the "rotting" erosion seen on the rocks. Is moisture involved? Or is it radiation? Such fine scale layering suggests sediment in water and yet... something isn't right. That may be too simple an answer. Could there be sedimentation in some other fluid?

Could sediments form in liquid CO2 as an example, and could they then be distinguished from water-formed sediments?

If ash, where is the source?

How old are these formations?

Etc.

Cheers, BRFelix