I think Robert Clark, JMS, Doug, Tom would agree
that some of the more interesting images from the MERs
are now in archives...I've dug this exciting one up from Spirit's
Sol 376 raw images [The micro-images].

The URL is:
http://marsrovers.jpl.nasa.gov/gallery/all/2/m/376/2m159745460effa2hpp22957m2m1.html

That's a corner of a ratted hole [probably the PEACE rock], and it shows a pale lumpy extrusion that appears to have oozed and refrozen.
Cause and affect?
I think so.

When the RAT device on the MERs grinds into a rock, heat is generated. Simple physics.

Notice that the lumpy pale material appears to droop near the edge of the RAT hole, as if it had oozed and flowed syrup-like.
Wouldn't it be exciting, Robert, to find that the heat generated by the Spirit's RAT device, grinding away on the PEACE rock, actually caused
some lumpy [salty? frozen?] plastesized material to thaw and flow, or ooze.
It sure the hey looks like it.

I can't think of a better explanation. Can you, JMS? Nick?

Jacob