Hort,Nice animation. Looks like a crust...

Hort,
Nice animation. Looks like a crust (layer of duricrust) over the soil. In fact the overlying the surface look as if they may be fragments of duricrust. Certainly that is what I would think were this taken on earth.

Not sure about your icy soil sublimating. Need to see it with the same illumination noting the significant change in brightness (same filter?.