Looking at this:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA17761
I think a few small pebbles slightly below the rock moved too.

Before and after shots of the disturbance. It seems to have dislodged a large rock. Below and to the left of the moved rock, there may be a smaller disturbed area partly in shadow.

Marsquake? Or should we see more substantial alteration to the enviroment? Wait for MRO check for impact theory, if none, then a bit of back tracking might reveal more moving rocks and pebbles.

Hey marsophile, what image is that on the left side of your composite?

From my observations of the testbed when driving and turning on hard surfaces, the right rocker can store large amounts of energy in the deflection during a turn or a drive. When the energy gets released it is released in a very short amount of time and has quite a punch. So *I* would not be surprised if PI was kicked by the RF wheel using energy stored in the strut during a maneuver. See, not only the rock was moved, but also turned upside down, I think. I doubt we will ever know what really happened.

I also think that Oppy is just trying to steal some of the attention Curry is getting.

Paolo

http://marsrovers.jpl.nasa.gov/gallery/all...DPP1214L0M1.JPG

Front hazcam from Sol 3514.

By the way I had to manually massage the right image (rear hazcam Sol 3540 taken from further away) to get it to approaximately match the perspective. I stretched the Y-coord, rotated, and then squeezed the X.

Very interesting and illuminating Paolo. I had visions of this monotonously slow crawl, its good to know Oppy has some 'spunk' in its legs!

In the dislodged rock from marsophile's 'Before and after' sequence a few posts above, the area 'kicked up' is so flat that it is surprising a rock could have been pulled up, as its definitely a rock and not a 'divot' as evident in the xeye below. That it was actually exhumed without any apparent prominent feature that the wheel could 'hook' onto to pull it up so the wheel must have had to dig in to something at just the right place to pull it up.

That said, it doesn't seem obvious as the source for PI, though there isn't enough detail to be sure, its could be a broke-off section of it..

Yeah, thanks Paolo for that insight.

In today's teleconference, Squyres thought that the source of PI is currently out of view below the rover. They plan to move and image the area to try locate it.

Speaking of moving, there was a tiny shift in position on 3555 (with new rhazcams). Compare these frames:
http://qt.exploratorium.edu/mars/opportuni...0M1.JPG?sol3551
http://qt.exploratorium.edu/mars/opportuni...0M1.JPG?sol3555

There seem to be some raised parts that might have provided leverage. [EDIT: It's like the old gag where someone steps on the teeth of a garden rake, and the pole jumps up and hits him in the face.]

My idea:
First the wheels of Opportunity had loosen the little rock out of the ground, increasing its wind attack surface.
Second step is the wind that came and blew it down the slope.
Do we have any knowledge about the weight of this piece?
And what about wind speed during the last sols?

If there was a wind so powerful to move and turn over this rock, the solar deck would as clean as new and we would definitely know about it.

Paolo

PS: Happy 10 to all of you.

Sorry, Paolo, but I can't imagine even a storm cleaning the solar cells.
I never had a clean car after I ran the German Autobahn.

Here's an interesting factoid I learned while doing book research: wind more readily lifts sand-sized particles than clay-sized particles, both on Earth and on Mars. It was a mystery until pretty recently how dust was getting lifted off the Martian ground into the atmosphere, when sand didn't seem to move much. Dust devils seen by MGS provided one answer, with their vacuuming effect -- that could lift dust, while straight-line winds couldn't. Then Spirit's MI provided another answer, showing that dust on rocks in Gusev had clumped into aggregates large enough for the wind to effectively pick up before the aggregates poofed apart into their component dust particles. So if you see a surface that's really coated by really fine dust, it's not obvious that even a strong wind will clear that dust off, yet another reason that the fact that cleaning events happen is such a pleasant surprise.

Parallel-eye, not cross-eye, for better depth perception.

Yesterday's rear hazcam gives a better view of the divot area. The moved rock seems to have broken into two pieces. The upper piece has a cavity.