re: Besides...
I wasn't very precise in my post. What I was specifically referring to was the reddish material in the middle of the trench. It has the appearance of mud or clay. Google "Magic Carpet" and "MER rover" for similar looking material early in the MER Spirit mission. Note that members of the MER rover team have already argued some rocks in Gusev have APXS signatures that are best expained by clays.
I agree the whitish material is most likely salts or sulfates. I wasn't arguing this was ice.
Bob Clark