The location may be solved but we still have two hypotheses for the formation of the bright componenet. It's either formed recently near the surface or it is a serendipitous exposure of something ancient. I'm going with number one. There is some water vapour in the air and it must go through cycles of condensation and sublimation. There will be an active layer at some depth where crystals form, like desert roses in Arabia. Maybe that layer is just a couple of centimetres down and we're seeing the products here.

http://i1.trekearth.com/photos/108334/_dsc4210_800.jpg

On the other hand - that suggests the products should be found almost everywhere. An excavated stratum of unusual material could be much more limited in extent. Maybe mapping occurrences of rocks like this around the hilltop will help resolve the question.

Phil

I think I would punt for number two ngunn. Given the miniscule absolute humidity and temperatures it is extremely difficult to see how manganese iron oxide crystals could form, recently, near the surface and internal to Stuart Island, which in itself is potentially an eroded out clast. The Manganese iron oxide crystals alone would seem to point towards a hydrothermal deposition. High magnesium and sulphur content implies a magnesium sulphate. No idea of the hydration state but there would be a high probability that this also formed by ground water mobilisation. We have seen enough kieserite since landing in Eagle crater to imply that water deposition from the atmosphere is effectively non-existent.

As atomoid reminds us, Oppy's lost bits of hardware before. But I don't think this is a nut, as much as it might look like one:
Click to view attachment
Probably just a fragment of rock from the PI-forming incident.

Edit: this frame from the current location just missed capturing the "nut" at higher resolution:
http://qt.exploratorium.edu/mars/opportuni...5M1.JPG?sol3571

The sol 3578 images:


http://www.midnightplanets.com/web/MERB/sol/03578.html

seem to show the right front wheel driving right over Pinnacle Island - an attempt to crush it, probably.

Phil

Hmm... I've been wishing they'd do that, but I think PI is still safely at the bottom of this image, uncrushed, unless I'm missing something. Probably just repositioning, but I do hope they run over it again, and maybe crush some other rocks for good measure!

Oh, right... there are later images, but it's another rock the wheel has probably run over.

Phil

omg, all of this talk about the violent treatment of rocks has left me feeling faint.

http://marsrovers.nasa.gov/gallery/all/1/p...FCP2535R7M1.JPG

The dark rock on the right looks different from this earlier image.

[EDIT: Sorry for being unclear. Comparing the above image to the image linked in mhoward's post:

http://www.midnightplanets.com/web/MERB/im...4P1205R0M1.html

there is a very dark rock that appears to have been crushed. That it is the same is evident from the bedrock underneath although the perspective is quite different. (I think the rock is in one piece in the prior image although it looks cracked and is partially in shadow.)]

Which two images are you comparing, marsophile?

As expected, a fragment it is:
Click to view attachment

Click to view attachment

On second thoughts, it might be an illusion caused by the change in perspective. The rock looks pretty beaten up even in this earlier image.

The Navcam images from Sol 3571 and Sol 3573 stitched together.

Jan van Driel

Click to view attachment

As an alternative to truly 'ancient' deposits (hundreds of thousands of years, rather than billions), might it be plausible for the source of humidity to be associated with a recent Milankovitch epoch, one in which an overlying snowpack drift accumulates against and outcrop and becomes buried by blowing sand to linger below the surface long enough to eventually interact and form deposits like this? and the non-ubiquity of such deposits be explained by the initial uneven formation and weathering in the intervening eons?

I appreciate both replies on this topic. Regarding the unusual elemental composition, undoubtedly that has to have arrived with the rock itself. That's no surprise. We know the sediments here contain fragments of many different types of source rock, no doubt from diverse locations traversed by the episodic flooding events. So far I'm with serpens. That said, I also think it's likely that atypical rocks that find themselves just centimetres below a freshly exposed surface as erosion proceeds will undergo at that stage more rapid changes than they have done during long term burial. In particular they will be subject to temperature variations and perhaps humidity cycles too: daily, yearly and astronomical (Croll-Milankovich). Also pH changes. So recent recrystallisation processes have to be considered a possibility.

Temperature is a limiting factor for formation of manganese iron oxide so a bit more than snow or humidity would seem to be necessary. Other than hydrothermal, I guess the most likely mechanism would be formation of bixbyite in the high temperature, steam rich impact cloud when Endeavour formed. Both scenarios would explain the positioning in rim breccia.

Couldn't the manganese be in some form other than manganese iron oxide? For example, permanganate? How would that affect the possible genesis and the formation temperature?

If they state that they identified manganese iron oxide then I think we can accept that that is what it is. Pity the Mossbauer ran out of oomph but they can be pretty definitive in this case using the APXS and visual MI.

I'm well out of my depth here on the mineralogy and happy to defer to more knowledgable posters, but I found a couple of things that may be relevant. First I note that bixbyite is a black mineral whereas the encrustation around the perimeter of Pinnacle Island is light toned (maybe white?), so perhaps we're talking about two different parts of the same rock. On another tack, I came across this: http://www.google.co.uk/url?sa=t&rct=j...ZGU&cad=rja

Ray Arvidson's statement that "The dark red stuff appears to be "iron manganese oxide of some kind," while the surrounding white part "represents some kind of sulphate." Given that Pinnacle Island has a high magnesium content, magnesium sulphate seems a likely contender. Hopefully all will be revealed at the next LSPC.

The L0 Panoramic view from Sol 3578-3579-3581.

Jan van Driel

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Wish for Opportunity to crush more rocks: granted. 'Sledge Island', Sol 3585

crosseye from sol 3587 90-cw rotated MI pair centering on the topmost part of the crush zone highlighted in mhoward's post above.
Click to view attachment

Oops, clumsy! They broke Stuart Island.

http://www.midnightplanets.com/web/MERB/im...8P2545L4M1.html

Phil

Wow. Oppy does Karate!

Amazingly fragile rocks.

"Nice rocks ya' got here. It'd be a real shame if something 'happened' to them..."

Clouseau strikes again.

"That was a priceless rock!"

"Not any more."

Hey Boss, you want I should give 'em the clamps?

Tonight on Ethel the Frog, we look at Opportunity's obsession that she is being followed by an enormous indurated breccia named Spiny Norman...



-the other Doug

Oppy: "Aww, it was already cracked and would have fallen apart on its own,
Click to view attachment road hazard is now in more manageable pieces!" Click to view attachment

Monthy Phyton.

Oppy's continuing to produce impressive power for this time of year - just past solstice and she's up to 464 Whr!

From the latest update.

I did not know they were using the IDD to crush rocks.

Did you also note that people's pictures who write the updates didn't change till 2004? Oppy's still a young lady...

I didn't know it either, and I believe I was on shift that day...

Paolo

Whoa!! This last update show a solar array dust factor of 0,691 when the lattest were 0,610;0,590 and 0,594. So, a relatively big cleening event had happened during this last week. Thanks to wind god of Mars (the same of earth; eole?).

Good point Cruzeiro do Sul. It depends on which mythology you base the naming on I guess. In normal use here on Terra we tend to use the term Aeolian based on the Greek god of the winds Aeolus, although non traditionalists use eolian. But we are now discussing Mars and since that relates to the Roman god of war then we should probably use the Roman wind gods, Venti.

Both mythologies are referenced in scientific jargon. For example, you'll see discussions of aeolian erosion forming ventifact rocks...

-the other Doug

Aeolus held the winds in a bag. What did Venti keep them in? A really big cup?

Phil

Some details about the recent dust cleaning (venti-lation?) in the latest PS report:

After reading that in the report I was immediately thinking about the way that sand blows off the top of a dune keeping it almost in continuous motion even in the lightest of winds.

Click to view attachment

I think the total tilt (vector sum of North/South and East/West) has been greater recently than at most times in the past. Perhaps that might account for the steady improvement? If this is so, then it might be useful to seek a tilt (perhaps East/West) even during other seasons besides winter.

Spirit overwintered on the northern edge of Home Plate and got some pretty extreme tilts, but I don't recall any particular effect on dust coverage.

My guess is that the gravitational forces on dust on a tilted panel would be tiny compared to the wind forces.

I don't think it's just a matter of tilt. It's more effective for dust cleaning to tilt into a prevailing wind, I think -- it increases the force of the wind for the surface to be more perpendicular to the airflow. Obviously, the edge of Home Plate wasn't an area where there was much prevailing wind. I'd guess there is more wind where Oppy sits now than there is down on the plains. I think the two -- a windy location plus a tilt into the wind -- worked together to create a gradual cleaning effect.

-the other Doug

That sounds right to me. A location where the hillside already faces into the wind plus an extra tilt of the panel in the same direction does the job. The dust is being swept upward off the surface, not sliding downward due to gravity, so tilting alone without the prevailing wind and the right topography would accomplish nothing.

The fact that this is a location where loose surface material is preferentially removed by wind may be part of the reason why we're at this spot.

I'm still not convinced that the tilt is a factor here. I'd say that the wind along a slope is more or less parallel to the slope. If the wind was directed into the slope, the air would have to compress, which it doesn't do (significantly, anyway). Oppy's panels are tilted compared to level, but they are more or less parallel to the local slope. So the wind should be blowing more or less parallel to the panels, like it did when we were out on the plains.

But the topography could somehow give us stronger winds than we've seen before. Or turbulent lee eddies that might be good at cleaning dust of the panels.

I'm looking at Astro0's picture in post 191. Which way would you want to tilt to get your panels cleaned? I'd go for down slope and into the wind.

I'm with fredk in that Opportunity's solar panels are always pretty much parallel to the terrain and wind. But despite lots of erudite articles and hypotheses the mechanism behind the cleaning events remains something of a mystery. From Larry Crumpler's contour map, during Opportunity's climb up the Solander ridge the topography would seem to put her in a zone of lower pressure and higher velocity. Yellow-bellied glider however raises the question as to what is a drift of pure dust doing in what should be a material removal zone? However, with the need for a northerly tilt for power, for much of the time it would seem that the solar panels would have been at a slight negative angle to the prevailing wind so turbulence, as suggested by fredk, does explain the continued removal, particularly if turbulence is a factor in the electrostatic charge of the dust.

Sol 3596 mastcam pan:
Click to view attachment

Given the slow but steady dust removal, I wonder if it might be worth leaving the MiniTes window open again for a while in the hopes that the MT might be restored?