That's interesting
The Spirit team seems to be fascinated with this:
http://marsrovers.jpl.nasa.gov/gallery/all/2/m/160/2M140565777EFF6900P2906M2M1.HTML
The last image in the series seems to focus on what is either a spiral structure or simply debris gathered on a rutted surface
I think I figured it out: the hectic Mars schedule means they're not eating very well, and thus "blueberries" will be joined by "spiralli" pasta
following there is a series of closeups, all out of focus and not corrected, so you can't tell what they were so interested in, or if they simply missed it
Usually at the "end of the rainbow" the wee people left a pot o' gold...