For some reason I am thinking of Wopmay....

I was looking forward to this month's Mars Exploration Rovers Update from the Planetary Society's Salley Rayl, which has become our main point of contact with the MER teams. I hope it's simply a little later than usual rather than discontinued. Emily?

I was wondering too, and checked this morning. It's just running late. I'm not sure when we'll get it, but we'll get it!

I certainly couldn't dispute that hypothesis, given what we now know.

Funny coincidence! As I was doing the dishes last night, "Wopmay" suddenly came into my mind, and I was remembering the wonderful images as we sidled along Burns Cliff. Seems another lifetime ago...

When I first did see these images I did indeed think it might be the actual edge for Endeavour crater.
And made of material that were older than the impact that created Endeavour.

And then reading here that this spot might be related to clays also, even better!
Now that some of you say it might be blueberries here after all, I cannot get the ideas of what we got here to match with each other.
Also I have to admit having a very limited knowledge in geology, I still had the notion that the phyllosilicate layers would not come with blueberries.

Well, the first MI's are down:
http://qt.exploratorium.edu/mars/opportuni...2M1.JPG?sol3064
They are pretty spherical, but they seem to be embedded differently from what we've seen with blueberries...?

And I don't recall seeing outcrops quite like these before:
http://qt.exploratorium.edu/mars/opportuni...5M1.JPG?sol3064
I can't wait to see these in colour...

It really looks like we have two different units here: the dark-colored rock at bottom left and on the left, and the light-colored rock on the right and at upper right:
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You don't have to...


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Sol 3064 L257 un-adjusted

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I tend to agree that it look somewhat different, lets hear what any of our semi-pro's think.

Perhaps it is so charborob, yet look at this navcam image
http://qt.exploratorium.edu/mars/opportuni...M5P1961L0M3.JPG

The lighter material at left, might be the same as we see at center bottom and in the lower right corner. Those two latter ones might just be less wind eroded.

Amazing stuff. This is the view west and 20º down.

The "melt"-like stuff reminds me of that one small crater Opportunity explored some months before getting to Endeavour. I'm blanking on the name at the moment. But of course it may be completely different. This looks more like it's part of the rock.

Maybe you're thinking of these: "Oppy has finished her studies of the Chocolate Hills, and has moved off to the left, resuming her circumnavigation of Concepcion Crater."
Farewell, Chocolate Hills…

But remember, that was melt in Meridiani sulfate rock and we're hoping this is something else.

A couple of MI mosaics...

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We really need a "shakes head in wonder" icon...

. . but range widely in size and seem to like splitting in half. Interesting times.

I believe we established quite a while ago that hematite concretions like the blueberries are resistant to melting. This looks like breccia with partially broken-up concretions as the clasts within the breccia. The matrix appears quite uniform.

My best guess is that there were concretions in the soil when the Endeavour impact occurred, and what we see here is impact melt that gathered up the unmelted concretions in the debris cloud as it cooled, making it impact melt breccia with concretion clasts.

In other words, it's blueberry muffin rock.

-the other Doug

Those MIs are astonishing- so fabulous to see something so radically new from a nearly 9-year-old rover! I'm betting against blueberries- these rocks, and the pre-exisiting rocks they might have been derived from in the Endeavour impact, are much older than the blueberry-containing formations so it's perhaps unlikely that they would also have contained blueberries. These guys tend to have resistant outer shells, which I don't think I've ever seen in blueberries (though on oDoug's hypothesis, maybe the outer layers were melted and hardened in the impact?).

I'm betting on these being tektite-like spheres of glassy impact melt...

John

A couple quick color anaglyphs

If that's the case they were formed long before the sulfate layer blueberries we are used to seeing and under different circumstances.

What the heck...??!?!! (And, Stu, brilliant work; thanks!!!)

I think that they pretty much have to be blueberries, albeit perhaps of a different vintage than we are used to. They didn't get a chance to get very much larger.

Perhaps a significant clue to the history of the Endeavour impact site.

Thanks, Nick. You liked that..?

You'll love this...


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Beautiful mosaic.

These appear very different from the blubes we're accustomed to seeing. Glassy impact spherules would be my best guess, too, after seeing the MIs.

We're still missing the R5 filters, so I can't do a hematite image yet.

These somewhat resemble devitrification spherulites (a type of spherule) that form during the localized crystallization of water-bearing glass, although the glass involved is usually more silica-rich (e.g., obsidian) than what was likely the case here. Such spherules can be hollow on the inside, owing to steam released during crystallization; large hollows are called lithophysae. (Many years ago I did much field and theoretical work on lithophysae containing gem topaz.) Spherulites can be more resistant to erosion than the rapidly altering remnant glass that surrounds them. Just another possibility to add to those already suggested.

Is that a glint of sunlight on one of the nodules near the top center (of Stu's pan), or just an artifact?
What a place!

What? Another type of spherule in Meridiani? This is just too much. Oppy has clearly been out of the limelight too long, they need to hold another press conference and get Steve there to explain it all.

what a place indeed... Oppy steals the show!!

i think your referring to the right side of the top left quadrant of Stu's wonderful MI mosaic
i see those from time to time, i think its just too bright for the sensor at the exposure level so it bleeds out a bit, perhaps..
im curious about the bloob just to the left of that bright glinting one, it has lines running diagonal to lower right. its kinda really strange, i dont see anythingn quite like it, i dont quite know what to make of it...

the cache of blueberries is so startlingly concentrated here, and since im not a geologist and have no reputation to lose I will go far out on my own breaking limb to suggest they didnt form in situ but were collected by erosional processes rolling into collecting cracks with a subsequent Endeavor impact resultant water percolation cooking them up with rinds and modified materials into something like a blueberry mud muffin cake layer filling, whatever it was it sure looks delicious!!
..but i sure do like the sound of the phrase ".. impact melt breccia with concretion clasts.." (thanks 'other Doug')

I've been looking at these spherules and wondreing about the "rind" we see on many of them. You're probably close. Get a larger sample of examples with more images, get some idea of the color, maybe hit a flat surface with the snaggle-toothed RAT to get a fresh x-sectional view. And so forth.

I think these MIs are a view of the light-toned flat rocks, we haven't even gotten to the dark, coarse-textured ones yet!

--Bill


CR: you may be right. On second glance, it's not looking like the light-toned flat rock.

I'm hoping someone can post a context image showing us where these MI's were taken. It seems that the MIs display a denser concentration of spherules than many of the rocks we see in the pancams.

There are an endless variety of spherules. Geologists love spherules.

These have a passing resemblance to the Gunflint Lake lapilli deposit originating from the Sudbury impact. (image source Minnesota Geological Survey). If these are lapilli would that not imply that the deposit was laid down at a distance from the impact site which would be a strong indicator that these were part of the pre-Endeavour impact terrain?

http://i1191.photobucket.com/albums/z468/s...pactlapilli.jpg

I was thinking the same thing. As far as I understand it, a crater rim consists of preexisting target rock layers, usually overturned by the impact excavation process. I would think that most glass would be deposited with the impact ejecta, not in the crater rim. So if these are impact spherules, I don't think they could be from the Endeavour-forming impact, unless Endeavour's current "rim" is not actually the original rim but instead an erosional remnant of the ejecta deposited outside the rim, which turned out to be more resistant to erosion than the actual rim.

But this is all pretty arm-wavey geology. I need to go talk to an impact person, ideally someone who's familiar with the rover mission. I don't actually know anyone who answers that description. Hmm.

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Know not suppossed to clutter but gotta say WOW OPPY.

Not even going to pretend to be a geologist.

This just proves the benefit of having long lasting rovers..... I remind my non-space following friends that Mars is a world and seeing ONE landing site area does not define the planet.

Keep going OPPY team!!!!

Craig

Could anyone recall the composition of Wopmay back in Endurance crater and the chocolate hills at Conception crater!?? I see a resemblance in these rocks here !!

Indeed, this fits very well with the observed textures of the bedding, etc, at this outcrop.

A quick reference to clastic dikes:

http://en.wikipedia.org/wiki/Clastic_dike

They can be relatively benign, like from fluidized injection from the weight of overlying strata, or by the sweeping of sediment into open fractures (like dessication cracks or the Anatolia lineations) or catastrophically, related to impact processes:

http://en.wikipedia.org/wiki/Upheaval_Dome

Your image is labeled "bonner clastic dike"-- what location/formatin is that? "Bonner" makes me think "Idaho".

From yesterday's color Pancams, the Blue of these spherules suggests to me more of an impact melt instead of an hematite concretion. FWIW.

--Bill

Wopmay was, IIRC, Burns Formation with Blueberry concretions. Chocolate Hills was apparently a fracture fill.

--Bill

Wopmay and Chocolate Hills are altered pieces of Meridiani sulfate layers. These layers were laid down over millions of years on top of the older surface that Endeavour crater was formed on. Hopefully the rocks that Opportunity is looking at now are part of that older surface. If so, although they may resemble Wopmay and Chocolate Hills, they would have a totally different composition and history.

If this rock is Noachian aged, maybe it dates from the period of the Late Heavy Bombardment. Impact lapilli might be common in rocks from that period.

That said, I thought that impact lapilli were supposed to come in discrete layers. These look to be scattered evenly though the rock.

Nobody has said anything about the matrix. I think there is an excellent chance that the matrix is the source of the clays, but last night I compared the route map with the map of the clays from CRISM and noticed that the rover is a little north of the area where clays have been detected.

1/ The upstanding 'fin-like' outcrop could in its entirity be considered a discrete layer. I'm not yet sure whether we are looking at a coherent stack of everted rim bedrock or a rubble-pile of ejecta in which the 'fin' is just one largish fragment that happens to be partly on edge at a plausible angle. Either way I'm with the pre-Endeavour impact lapilli idea for now.

2/ This is quite a small outcrop and any patch of clay minerals deriving from it may be too small for CRISM to resolve. There could still be clays to be found here, though undoubtedly there's a bigger patch up ahead. Will that prove to be associated with more exposures of lapilli-packed rocks? With luck we'll soon find out.

If they are lapilli, they may have been mixed with other material by impact or some other process, the mixture later becoming lithified.

You can almost feel your boots skidding on these beautiful rocks as you clamber and step over them, can't you..?

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Me, too.
It seemed to me that we should be able to make some guesses about the ages of these rocks from their dips and strikes, so I took a look around.

Lapilli are a very specific type of spherule. Should we expect a certain kind of internal structure in them as compared to glassy spherules?

I'm not sure, but since the apparent rim of Endeavour as seen topographically appears to be discontinuous and significantly eroded (and, since we are all making wild guesses here lately), I'll guess we are somewhat outside of the original rim.

From the split examples in the MI they look more like a product of accretion than condensation - maybe perhaps.

As a non-geologist I'm here to learn from those who are, and I'd appreciate some help with definitions. Here: http://www.google.co.uk/url?sa=t&rct=j...KDA&cad=rja I read that lapilli are small round stones produced by volcanic eruptions or meteorite impacts and that they can be formed either by accretion from a vapour cloud or by solidification of drops of melt. Is that how you're using the term, and if so what is the distinction between the latter case and the glassy spherules you refer to?

(I do apologise for descending into semantics but I want to make sure that my posts do not muddy this fascinating discussion through loose use of terminology on my part.)

Does anyone know of a cross section of a tektite? This is the only image I could find online:
http://www.panoramio.com/photo/3894593

The latest MI shot shows the cross section structure a bit better http://qt.exploratorium.edu/mars/opportuni...M5P2935M2M3.JPG

They do bear a superficial similarity to the very last image on this page http://www.meteorite-times.com/Back_Links/...te_of_Month.htm

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Tektites are glassy bits of impact melt that hardened in the air; their shape need not be spherical, and they are probably irrelevant to the subject of this discussion. Lapilli are gravel-sized fallen melt stones, without reference to specific shape or origin (only size), and the term alone therefore is ambiguous.

As is being discussed, there are many types of spherules and other intrinsically rounded objects, of various origins. Spherules formed by some combination of chemical and physical accretion, such as concretions (formed by pure chemical accretion owing to abrupt changes in chemical properties of groundwater that reduce mineral solubility) and accretionary lapilli (formed by a combination of condensation and physical accretion - possibly involving electrostatic charge - of particles in a turbulent, cooling and mixing gas cloud, and thus not unlike hailstones in concept) are NOT HOLLOW on the inside, unless perhaps internally weathered or altered (as most are on Earth).

The spherules under discussion, or at least many of them, ARE distinctly hollow, and some appear to have objects in their center. This feature (hollow, possibly with junk on the inside) is characteristic of spherules formed by devitrificationof a hot hydrous glass, especially of the variety called lithophysae. As microcrystallites of anhydrous silicate minerals grow radially outwards, in many cases around a central object or megacrystal that served as a nucleus, they release steam that can inflate the spherule as it grows, leading to a hollow inside (except perhaps for the remant central object). The images haven't shown any yet, but some lithophysae even develop an onion-like or layered outer structure (but with open space between the layers), as a rind of crystallites develops, then steam escapes past it, inflating the still soft hot glass, then another rind of crystallites grows, and so on.

Oppy may have been imaging impact glass cementing breccia ever since it arrived at Cape York. Martian impact glasses and melts, compared to those found elsewhere, should be especially hydrous and full of salts, both of which characteristics would favor devitrification (crystallization), so finding spherules formed by devitrification of hot glass or melt shouldn't be surprising. I repeat, this is just one suggestion among many, and need not be correct, but it appears to be the only one so far that accounts for the intrinsically hollow structure with junk inside and an apparent rind on the outside that has just been imaged here. Greater magnification revealing a concentric outer rind of microcrystallites (as mentioned by Bill Harris above), or new images revealing a separated outer onion-skin structure, both would support the hypothesis. I hope this background information helps the discussion.

It certainly helps me make sense of it. Much appreciated.

After years of sulphate sandstone and a winter looking at a chunk of suevite this is ultra cool. There does not seem to be much deformation in the spherules and if they are devitrified glass wouldn't this indicate a lack of compaction? ie. If they were formed pre-Endeavour then they would have been deposited pretty close to the old surface . A thin section of unweathered rock would come in handy about now. I wonder if the APXS will be able to provide an indication of the nature of the matrix? The next Opportunity related LPSC papers should be real interesting.

Edit: Just to put CosmicRocker's look around in context, is this a view of the outcrop from the Sol 2751 position?

http://marsrover.nasa.gov/gallery/all/1/n/...J7P1907R0M1.JPG