re: That top layer of dust is probably uniform
I agree the surface is pretty uniform. But I don't see why the structures below would be any less uniform.
I suspect if they wanted to reenact the problem all it would take is hitting a hill at the right angle and pushing hard. So just avoiding the repetition of the actions that stuck them before is all that is need.
I could be wrong. Maybe tomorrow they will sink "knee" deep in the sands again.
