For those of you across the pond, read "Analogs"...

Erosion on Earth involves production of sediment which is reduced in size (comminuted) by transport and collision processes. Since this is often in an aqueous environment, water is always present as a buffer between colliding grains, limiting the size to which they can be reduced. One example of this is that aeolian sands have finer and more spherical grains than water-lain sands, enabling diagnosis of the origin of particular sand grains.

In desert environments, large amounts of very fine dust can be pruced by mechanical erosion of rocks in ways that would not occur underwater.

An additional aspect is that if you mechanically break grains of minerals, the surfaces are reactive and unstable. Placing these in an aqueous environment laden with solutes is a good way to "quench" the surface reactivity. Mechanically ground minerals have different properties than those ground into a paste while wet.

An alternative environment is glaciers, where rocks are ground against one another in the basal layer of the glacier as it rides over bedrock, generating a product known as "rock flour". This is a very fine grained mixture of mechanically ground minerals, with odd properties. For instance, rock flour is used in agriculture as a way of adding bio-available minerals to the soil (for reasons clear from the preceding para).

This surface reactivity also leads to interesting dielectric (radar) properties and probably a whiole bunch else. And remember, that on Earth, most samples of natural rock flour have already got a little wet in the periglacial environment or in wet-based glaciers. Imagine this stuff produced over aeons of aeolian action, exposed to strong UV and cosmic rays, and then laid down as dust on the surface. Perhaps this is where some of the strange properties of "magic carpet" come from?

Follow some of these links for interesting info.

Note that despite the analogy to environments on Earth, I don't claim that the magic carpet originated by glacial action, or even in a direct analogue to deserts on Earth. The full story is likely to have a typical Martian twist to it!