The formations look like cyrstalized salt
http://www.csulb.edu/~azary/slideshows/dl/DL3CA96-DthVal-SaltCrystals.jpg
Bewildered wrote:
>
> from
> http://qt.exploratorium.edu/mars/spirit/micro_imager/2004-03-16/2M132663815EFF1800P2973M2M1.JPG
>
> under the horizontal ridge
>
> [Image]