re: Opinion
Why do I keep thinking that there's Trona or raw soda ash involved here as well. Raw soda ash doesn't have to be wet to look cohesive/prickly crystals, and is very porous (used in coloring fabrics). Volcanic and meteoric iron could also contribute to the redish color of the soda ash, the Martian UV light 'bleaches' the top layer to expose the darker layer beneath.