Yep... my bad.

That image is from Sol 3516. In Sol 3528 images, P.I. has not yet reached its destination, so that particular disturbed area could not be the origin of P.I. (EDIT: Unless it traveled very slowly.)

Steve Squyres on the Opportunity 10 year event:
2 theories about this rock's origin: either flicked by the wheels somehow, or a piece of new(!) crater ejecta: lots of sulfur, and apparently twice as much manganese as anything seen so far!

High manganese deposited along a fracture implies hydrothermal deposition.

Would manganese deposited hydrothermally be suspended in water in the form of a manganese salt? Or are there more complex chemical interactions which would keep manganese in suspension and then initiate its precipitation out of solution? And would this imply warm, or even hot water (i.e., would manganese come out of solution as the water cooled)?

-the other Doug

It's archived here:
http://www.ustream.tv/recorded/42795898

Skip to 25:20 for his comments on this rock/ejecta/thing. Squyres is skeptical of the ejecta theory, though Hirise would make certain...

In mhoward's comparison image, looks like there is a second rock as well (circled red) that wasn't there earlier.

You're right, Pando! Makes one wonder what else is around. I tried a few crazy comparisons between Navcam and Pancam images but haven't spotted any other bits yet.

This a time to play the 'Rolling stones' perhaps. =)

The trace of "rolling stone"

Click to view attachment

A closeup of Pando's comparison.

More likely oxidation Doug so hot hydrothermal isn't necessary to the process. Interestingly enough Mn deposition has been connected to the authigenic formation of Fe-rich smectites such as nontronite. Fe-Mn oxyhydroxides in hydrothermal fluids can undergo early diagenesis with smectites being the Fe sink and with Mn precipitating, principally as nodules. So the high manganese reading dovetails with the smectites identified from orbit.

An excellent point. the only way out of the conundrum seems to be we simply haven't seen the actual disturbed area from which PI originated,
unless it just so happened to be picked up and transported inside the wheel to be released in a perfect ready-to-roll configuration in order to get to its resting place.. that all sounds more plausible the more I think about it. but did the sequence of wheel maneuvers support such a scenario?
otherwise I hope its indeed ejecta and perhaps the source a new priority destination.

whatcha know.. this discussion is getting some press:
http://rt.com/news/mars-rover-rock-appear-650/
http://www.news.com.au/technology/science/...e-1226803349096

http://marsrovers.nasa.gov/gallery/all/1/p...EOP2596R1M1.JPG

There is another disturbed area imaged on Sol 3544.

I check Curiosity Rover's Raw images every day, I forgot about little Opportunity. Interesting how that rock got there.

I was searching for information on where it may be headed next? Once it has observed this location after the hibernation time. I can't find much on it.

"Hibernation" is a strong word - Oppy should be able to keep working all winter, although probably not driving too much. As for what's next, check out Tesheiner's post here.

Edit - Sorry, that link doesn't quite take me to the right page - Tesheiner's post is #314, on the previous page. (Is there a technical problem with linking to posts? I got the link from the "Post #314" on the upper right of Tesheiner's post.)

Gust of wind blowing across Endeavour on sol 3546, compared with a frame taken under very similar lighting on sol 3548:
Click to view attachment

I think this happens when posts get moved or deleted. The links can't cope with the renumbering that results.

Regarding the origins of the mystery rock, it seems possible that the accumulated torque of two wheels going from pigeon-toed position to straight-ahead could have had a hand in popping out a rock., ... well, after attempting to put it in writing, I think a simple GIF might say it better, albeit crudely:

Click to view attachment

Of course, the rocks would have to be perfectly situated and sticking out just high enough for the wheels to get a toehold, with one rock not willing to budge, the other more willing if properly persuaded.

(I'm aware of the many inaccuracies in the above illustration, such as wheel layout, type of rock I picked, and sure there are many more. I don't have time to correct them, just trying to convey idea of two rover wheels doing some prying-apart action. My apologies if someone already floated this idea!)

Here's something that Stu spotted that I think is quite interesting. It looks like a couple small rocks with long trails behind them. Stu created an animated GIF with lines next to the trail-like features; they're subtle. I looked up the images in MP for some context: the trails are not obviously downslope, they go more west-ish, although I suppose they could be a bit downslope locally, it's hard to tell. Stu gave me permission to post this to see what you think.

Are you aware that the front right steering actuator has been broken for 8 years? It doesn't steer - it's locked with 8 degrees of toe in.

Of course RF doesn't steer, but that still leaves three steering wheels. Walfy's idea actually sounds like the second good idea we've heard (after the obvious rock-popped-out-while-being-driven-over).

The basic problem is that Pinnacle Island moved a considerable distance, as the debris on its rover side indicates. The slopes here are fairly subtle, around 15 degrees. In Mars gravity, that seems to be too shallow for a rock shaped like PI to roll easily. So PI must have been given a kick somehow. Getting squeezed under a wheel, and now Walfy's idea are the only ideas that seem to work. (The wheel rotation speeds are so slow that I can't believe PI being trapped inside a wheel and then spat out. And the odds of a meteor strike nearby have to be incredibly small.)

I think the human eye is excellent at finding features like that, but I don't think these are trails left by rolling rocks. We know what disturbed soil looks like on Mars - I'd expect much more obvious darker patches due to the soil underneath being exposed (if these were recent, at least).

The turning of a steering actuator flicking a rock across the ground? Have you seen how slow the wheels steer? It's incredibly slow. Sorry - I don't buy it. Moreoever - how would a steering actuator throw a rock infront of the rover? Walfy's animation shows it being throw away from the rover....not right infront of it.

I don't know if it's ejecta...it does inherently seem unlikely - but it's not that far beyond the realm of possibility. The modern day cratering rate as derived from orbital discoveries is such that I believe it was characterized thus : Within the duration of one crewed surface mission of a martian year - statistically there would be a new impact crater formed within earshot. We've been here 5 martian years. It's far far from impossible that it could be a piece of ejecta. It could be a tiddlywink's like pinging of a rock from under a wheel. But a steering actuator didn't just flick a wheel several meters....I don't buy it.

http://spacecoalition.com/blog/new-info-mars-rock-mystery

"Candidate divot" hinted at in the interview. Which is good, indicating it's originally from close by and can be put in geological context.

If it is in fact from a crater, visiting something that fresh would be amazing for science return: seeing what else was excavated, maybe even the original meteorite itself if it was a small impact (say Heat Shield Rock sized)
Of course, even if Hirise/CTX spot something new we shouldn't get our hopes up to visit it right away. They'll probably have to wait for winter to end to actually be able to access it (and finish the science campaign right here at Solander).

Exactly. As Walfy's animation shows, the idea is not that the slow movement of the wheel while steering acted like a golf club or putter to shoot the rock out. Of course that could not happen. The idea is that the rock was stuck in place, which would not be surprizing. As the steering wheels turn against the rock, the force builds until the rock's connection to the ground snaps. Suddenly it's free and you'd expect it to move out faster than the speed of the steering wheels. And there would have been two steering steps, at the start and end of the turn - is it clear that neither could've snapped the rock out in the right direction? Perhaps it ricocheted off another wheel?

About ejecta, we need actual numbers to say anything definite about how likely a nearby hit is. But this is what makes me extremely sceptical: We've seen several meteors within pancam-shot of Oppy, but no evidence of recent hits (last 10 years, say) of meteors or ejecta. So what are the odds that when we do see a fresh piece of ejecta, it hit within a couple of metres of Oppy? Surely it would've been far more likely to hit a few years ago, say, and then we drove up to it. It's the close link with Oppy and the timing that strongly suggests a connection with the bump on 3540.

Probably what marsophile pointed out above:
http://marsrovers.nasa.gov/gallery/all/1/p...EOP2596R1M1.JPG
That's on the left-rear side of the rover.

Doug, you may know this: Is someone actually compiling MRO data to derive an impact probability for a given location on Mars within so-and-so many meters or km over a fixed timespan? If so, I'd guess that they're still acquiring data to firm up the model.

I agree with Fred in any case; odds are overwhelmingly in favor of this being an uprooted rock that was transported for a bit.

It's intriguing though that it has a 'very unusual composition'. Does that mean that all the rock at this spot is 'very unusual' or that this particular rock is atypical of its surroundings? In the latter case we are twice fortunate that an unlikely case of wheel tiddlywinks happened to turn up a very unusual rock.

Personally I think everything points to this special rock being spring-loaded. It was primed to leap in the air as soon as anybody touched it.

That is the most logical explanation to date Fred and Walfy. As previously mentioned this rock looks like it separated along a fracture which would permit the build up of force until the (hydrothermally derived) material deposited within the fracture gave way, providing a reasonably significant kick off velocity. This scenario would I think provide the necessary accumulation of force and instantaneous release, whereas a loose rock, even in duricrust would provide much less resistance and a more gradual release. I am not sure that the actual turning of a wheel would accumulate the necessary force and I would assume that there would be some feedback based control to preclude the wheel turning against significant resistance? I would therefore tend to punt for the RF 'frozen' wheel being the prime suspect as during a turn, for some encounter orientations, it would push against an obstacle rather than over-ride it and the inertia of the rover in the turn would provide a significant force.

Already done, put to paper, peer reviewed and published
http://www.sciencedirect.com/science/artic...019103513001693


Walfy's animation seemed to me to suggest it was just a steering actuator bashing something out the way - which I hope we all agree is just not going to happen.

The notion that rover motion (of any sort) could end up 'popping' a rock into motion is fine. This all falls under the tiddlywinks category, surely? It's really not a separate means of flinging material

Huh. Didn't know they'd found so many thus far. Thanks!

A few possible scenarios:

1. One rock acting as a lever, one rock acting as a fulcrum, the rover weight on the lever.

2. Rover starts passing over a slab with a hollow underneath. When the rover is halfway the rock breaks under the weight of the rover. The part that is not under the rover gets flung into the air by the force of the so-called normal reaction to the weight of the rover. (This is similar to Fredk's suggestion except it is the weight of the rover rather than the forward momentum that snaps and throws the rock.)

3. Ngunn's suggestion about spring-loading. The rock may have been under stress to begin with and Oppy's turn was the "straw that broke the camel's back."

4. The soil under the hard crust may be under pressure in places, or perhaps sparks or heat from the pressure of the rover weight reacted with some volatile.

More interesting than the origin may be what the rock can tell us about the subsurface. Perhaps we should try to duplicate the event that produced the rock in other likely places.

I'd have to say that walfy's suggestion sounds the most plausible to me. A rock propelled by stored-up energy from the rover's suspension/frame/wheels system during a turn just seems most likely to me; especially considering that we can see a similarly sized, disturbed area quite nearby, and aligned with the projected path of Oppy's wheel tracks.

Regarding the curious composition of P.I, we really don't know whether or not that is anamolous in this locality. Furthermore, we rarely, if ever, have seen Opportunity analyze the bottom side of a flipped-over piece of rock. Who knows which salts might have accumulated in that environment?

It's been a while since we've had a bonafide Martian mystery like this to unravel. Good work, everyone. This is fun.

Some post-brush Pancam images of Cape Elizabeth came down. The post-brush color of Cape Elizabeth looks a lot like the interior color of Pinnacle Island to me. Here's the L257:

I notice the dust factor has been steadily improving over the last several status reports.

The rover has been tilted during this period. I wonder if the simple fact of being tilted could affect the deposition/removal "budget" so that a small net deposition could be transformed to a small net removal. Presumably the deposition comes mostly from the vertical fall of dust so a tilted rover might present a smaller collection area. On the other hand, the wind might be primarily horizontal so a tilt might help there.

IMHO, I can't visualize a tiddlywink or leveraged snap-effect scenario really having enough rebound to push a rock more than a few cm, and though I might be completely wrong, this rock seems so crumbly its hard to see much stress building up.

While still somewhat far-fetched, though still seems most feasible to me (and I still don't know if the wheel configuration and maneuvers support it, because it requires the wheel to be upslope for the 'catch' and downslope for the 'release'), is the wheel abutting against the PI source and dislodging it so that it becomes deposited inside the interior of the wheel.
At this point when the wheel turns, since PI would lie flat as a sort of hemi-square wheel shape, it should, as the wheel turns slowly, usually become rotated to a near vertical orientation inside the wheel and so as the angle of lean transfers to the tip-over point, it could either be re-deposited back inside the wheel for another rotation, or if its on the edge of the wheel in the right configuration, can escape in that vertical orientation, and may accumulate some extra height if it hangs on long enough.
So then if the part of PI that then contacts the ground is not the square half, but is the roundish half, and the ground has enough slope to it (a 15 degree slope isn't quite trivial), PI may gain enough speed from that small drop to roll several revolutions until the square sections stall it to flop over into its current location.

The main problem with propelling PI is converting the very slow rover and wheel movement into rapid PI movement, and what you're saying about the rock inside the wheel hitting the "tipping point" as the wheel rotates sounds like it would do that. Getting PI out of the wheel sounds trickier. The wheel being on a slope might help - with the right tilt, PI would move outwards as well as downwards once it started to slide inside the wheel. You could use basic physics to work out PI's maximum speed as it left the wheel. Friction would make it slower though.

It would help to know exactly where PI came from and how far that is from it's current location. We have a candidate "divot" - it shouldn't be too hard to estimate the distance from there to it's current location. Of course turning in place and driving can do multiple damage to the ground, so the visible divot may be unrelated to PI, and the real source may be underneath us and invisible, at least until we move again.

http://marsrovers.jpl.nasa.gov/gallery/all...EOP1311L0M1.JPG

The "divot" and some of the area around it is visible in the rear hazcam from Sol 3540.

Click to view attachment

A closeup (but fisheye-distorted). Compare with

http://qt.exploratorium.edu/mars/opportuni...EOP2599R1M1.JPG

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.

Click to view attachment

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..
Click to view attachment

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

Click to view attachment

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.]