Up there the surface conditions are so harsh the blueberrys have to grow underground, sort of like truffles or potatoes.

And the residents used to have to mine them to get the fresh ones. After they had been on the surface for a while the wind-borne materaial caused them to become mineralized and very hard, inedible really.

If one enlarges the image they can see two tracks leading into the mine, for the little carts which hauled out the fresh blueberrys. The other tracks are artifacts of the enlarging process, the edge of the pixels, but the ones pointing into the mine are tracks.

Seem to be narrow gauge, which is what you'd expect, can't tell what the material is but would assume iron. This seems to be one of the larger mines, so one might expect that there is a buried city nearby, buried by more wind-borne dust. Elementary, really.

And some people doubt the existence of past life on Mars!!! My heart goes out to them.

Arf