When I was a kid we had an outdoor wood burning stove that we used to provide heat in the winter....It produced a lot of ash... if you dumped a pile of ash out and it got rained on you soy a rough textured surface.....(no I am NOT claiming it rains on mars- just drawing an anlogy with other fine particulates)

anyway once this ash was dessicated it would capture in incredible detail the fatures of any object that pressed into it...

The dust on mars is obviously fine, but appears to be cemented weakly in some way... (vacuum welding? )

Before any of you jump on me I am NOT suggesting any relation to wood burning stoves on mars, just pointing out that the soil resembles that more closely than anything else I can imagine... a fine particle mix lightly cemented by some process....