I had to hunt down the photos of a little experiment we conducted here at Podrock Labs.
This is dried cornstarch after a week. (Ignore the mold spots in any martian analog, if you please.)
Note the first and second order structures. Sorrry there is no scale bar. The container was about eight inches in diameter and the material about half an inch deep.
This month's Geology had an article about desication structures in the White Sands of New Mexico as analogs to Martian sulfates:
http://www.gsajournals.org/gsaonline/?request=get-abstract&doi=10.1130%2FG22101.1 (abstract only, full article to members)
or here:
http://www.news.ucdavis.edu/search/news_detail.lasso?id=7698
The article has more to do with the "fins" or "hedges" that are formed along the joint surfaces in desicating gypsum sands than regional structures, but I thought it was very interesting. These rocks may record several wet-dry cycles (of the distant past, IMO).
Space/Science » in reply to not solution: but desication.
Update: Desktop desication polygons