Thanks for that!

The images are in exploratorium (see Stu's post above), but they are stretched differently so the sun is very hard to make out.

Here is my version of the mosaic taken at Kirkwood.



James

At the right of that panorama there is a feature that seems to cut right through the strata. It has reddish-(covered) clay-like stuff at its centre and darker rocks either side. Any ideas? A crack filled from above?? or below??

Exploratorium_1
Exploratorium_2

Some stereo of the new spherules from sol 3064...
flicker gif
Click to view attachment

and a 30 sec video version thats a bit easier on the eyes...
http://youtu.be/goP-DYlSbs4

How odd. Watching that flicker gif, I feel this compulsion to do the time warp. Again.

Brian

Edit: Replaced the image with a crude stitch of all 4 frames, from sol 3064.

Click to view attachment

A jump to the left! Knees in tight...

Anyone else wonders what this "fibrous" part might be?

Click to view attachment

Edit: Ahh - only cracks with the right light/shadow combination.

The blueberries from sol 3064 make for great "piku-piku" super GIFs. I was unable to embed one in this forum, but they can all be viewed here.

Nice work walfy,
those piku-piku have come out really well.

I get the impression that at least half of the "spherules" are hemispheres, though with the shadows it is difficult to be sure.

If the hemispheres are broken spherules, they seem (especially in walfy's excellent 3D renderings above) to possess a distinctive radiating fibrous outer rind or shell, although the resolution could be better. This radiating fibrous texture most resembles the spherulitic texture produced by devitrification crystallization (see photo in Antonb's post #218 and the second photo in my post #237 above), but it might also be caused by other rapid radial growth mechanisms. This texture is not, AFAIK, seen in accretionary lapilli produced by impacts or volcanism, inasmuch these grow by random sticking of particles to a nucleus in a condensing turbulent cloud. It also does not resemble any internal structure seen in broken normal blue hematitic blueberries (nor does the central open cavity). The mystery remains.

Thanks for the input dburt. But the 'fibres' in ronald's post 367 image are not radial but seem to cross the spherule in approximately parallel directions as if in response to external shear stress after the spherule formed. As to how they formed I notice a nice irony(sorry) here. You say the blueberries formed in mid-air and these spherules formed in situ on the ground whereas if I understand things right most folks seem to be tending the opposite way in both cases.

The question is why the cracks, which to my overactive imagination seem to have been infiltrated resulting in veining?

ngunn may be right in that the cracks were due to (compaction?) stresses. Or it could be dburt's devitrification crystallization. But I would throw another hypothesis into the mix being rapid quenching of hot glass spherules causing the fracturing. That would of course require that the spherules dropped into water. I remember a paper a few years ago identifying this effect in an impact spherule layer - in South Africa I think. There do seem to be clasts included in some spherules which would point towards glass rich lapilli.

This hypothesis would of course require surface water and since the Miyamoto ejecta would have been hundreds of metres thick here the spherule layer would have to postdate that event. Also this would pretty much rule out the Endeavour impact. So a reasonably thin layer of spherules from another impact could have fallen into surface water overlaying the Miyampto ejecta blanket (the large channels to the south that cut the Miyamoto ejecta do make such a real possibility). This would then make the spherule layer part of the Endeavour uplift rim.

the fact that so may are semispheres tends to suggest radial crystalization is making them vulnerable to temperature shock induced erosion, otherwise we'd see less halving across the diameters and more random breakage, perhaps a common terran geological observation, no?

Click to view attachment
A higher resolution view of the fibrous example, (in parallel stereo).

Many seem to be confusing these so-called "fibers" (cross-cutting fractures, most likely; I agree with serpens on this) with the far more subtle radial growth textures (that is, super-fine fibrous crystals, at the limit of resolution of the best photos, radiating from the center) seen in the erosion-resistant outer shell or rind to which I was referring above. You have to look carefully at the images to see them. Again, refer to the photos in above posts 218 and 237 (lower photo) to see what I am comparing them to.

My initial impression of the "spherules of unknown affinity" was that they were zeolite, particularly by way of the fibrous radial structure seen in some of the split. I'm not a hard-rock type and this was from ig-met pet courses in school many years ago. I'll always remember the appearance of the hand specimens we had in the lab collection. I recalled that zeolites are secondary minerals created by the interaction of groundwater with volcanic rocks. I've since read up on the zeolite family and it is an interesting mineral.

As I said, I'm a soft-rock guy and I'll need to do considerable research on this or just listen to my betters...

--Bill

You mean formed as a devitrification product? The spherulites seem to be restricted to a reasonably thin layer and glass rich lapilli/devitrification don't seem to be mutually exclusive events particularly if the matrix is also glass.

Zeolites are a good suggestion. My colleague Steve Ruff has argued that they should be widespread on Mars. They commonly form, owing to the action of groundwater, in vesicles (gas cavities or bubbles) in cooling basaltic lava, and in this type of occurrence they are beloved of mineral collectors the world over. They require a more alkaline environment to form than the neutral environment of clay minerals or the acid environment of iron sulfates, owing to their high alkali content.

However, most are distinctly white or light-colored, and although some are fibrous or needle-like (acicular), they only loosely fill the cavities in which they are found. They typically do not constitute the resistant shells. I would therefore be somewhat surprised if the apparently micro-fibrous dark rinds of the hollow spherules in question were made up of zeolite minerals, although on Mars I would hesitate to exclude any possibility. This is all off the top of my head, of course. I'm giving a test and leading a field trip tomorrow, and am running more than a little late.

Yep, I keep hopping around on this and arm-waving. They might be devitrification byproducts, the probably aren't hematitic BlueBerries and they might even be something else. We won't know until we learn the mineralogy of this unit, and we won't learn that until The Big Paper comes out at LPSC.

I'm still leaning towards weathering and alteration byproducts on the pre-Endeavour land surface. This will certainly tell us much about Martian environmental conditions at that time.

"Zeolites" can have a very broad range of characteristics, much like the phyllosilicate family. I found a very interesting paper tonight on this subject:



--Bill

Fascinating stuff... what really gets me in marsophile's stereo view its dramatically apparent how the veined ('fibrous') section protrudes from the rock almost like planes of a desert rose suggesting it crystalized inside of, or more likely is an erosion resistant remnant of an eroded spherule interior.

note that no other spherules (afaik) exhibit this, suggesting (to my non-geologist eye) the veining formed through mineralization of fractures.

an odd puzzle is the fractures seem to occur in only this small area, not across a larger section as would be expected from slumpage or dessication, unless they did exist but were erased from erosion and this is all thats left

Pancam Sol 3084:

Click to view attachment Click to view attachment Click to view attachment

left is L3-L5-L6 (bit screwed up colours ), middle the usual L2-L5-L7, left a try on combining L7-R1

One more - L3-L5-L6 this time:

Whitewater Lake (used all 6 L filters for better colour and to reduce artefacts)

Sol 3085:

Click to view attachment

Get used to the view folks, we're going to be here a while.

http://www.jpl.nasa.gov/news/news.php?release=2012-306

One working hypothesis, out of several, is that the new-found spherules are also concretions but with a different composition. Others include that they may be accretionary lapilli formed in volcanic ash eruptions, impact spherules formed in impact events, or devitrification spherules resulting from formation of crystals from formerly melted material. There are other possibilities, too.


That's a subtle hint if I ever saw one.

Ah so. Matijevic Hill is the "official" name of the location that I had informally called "Shoemaker Bench". This will prove to be a great stop.

--Bill

Whitewater Lake RAT hole...

Click to view attachment

Looks soft as butter, isn't it?

I can't believe it's not butter...

This is important information I'd say! Soft as clay would be even nicer.

Tesheiner just set 'em up for you to knock 'em down

The softness of these rocks is crazy. I've been imagining Opportunity's wheels crunching like boots on rock but I'll bet that when there's gravel underfoot it doesn't crunch so much as grind; gravel between your foot and the rock might gouge its way in. On a field trip to west Texas while I was in college I encountered a rock made of bentonite -- it was able to form cliffs in the desert but walk on it and your boots gouged right in. It was weird stuff. (Here's a neat photo essay about that rock.)

My college geology field class drove past a bentonite mine in Wyoming -- the stuff was scooped right out of the hillside into rail cars. Bentonite has many uses, including incorporation into candy bars, which in this case could lead to a whole new meaning for Mars Bars. Here's a little more about bentonite -- note the rock-water interaction:

http://www.rawell.co.uk/products_technical...s_bentonite.php
Bentonite is a natural inert clay that was formed from volcanic activity during the Cretaceous period approximately 100 million years ago. Long periods of repeated eruptions laid ash into the sea where it was chemically altered and consolidated into layers of clay. Over time the ground folded and lifted thrusting up the clay and silt to form the Black Hills and Big Horn mountains of Wyoming, USA. The term bentonite is generally applied to colloidal clay associated with the Cretaceous Benton shale found near Fort Benton. Bentonite mining first began in 1888.

The first recorded use of the mineral known as “the clay of a thousand uses” was for making cosmetics, it then became used as a foundry sand bond in the 1920s followed soon after as a drilling mud. The uses have continued to expand into the fields of bleaching clay, animal feeds, pharmaceuticals, colloidal fillers for paints and inks, ceramics and in the motor industry for spark plugs and catalytic converters.

I wouldn't make too much of it being bentonite. I've seen kaolinite in east Alabama, chalk/marl in south Alabama, loess along the Missippi and bentonite in the Big Bend of Texas that all look similar. We can see/say that it is a soft, fine-grained, amorphous material of uncertain composition and origin.

Yeah, more arm-waving and hopping back-and-forth. Hot on the trail of a hypothesis...

--Bill

I wasn't suggesting Opportunity's rock is made of bentonite; I was just musing on how different the soft rock seems from what one normally thinks of as "rock."

Well it looks like mudstone/siltstone/clay - roll on the APXS results. I still think that this is a sedimentary construct resulting from the weathering of the Shoemaker deposit. Given that this weathered material would have encompassed igneous rocks and impact glass couldn't we expect a mixture of clay types, for example montmorillonite-chlorite, potentially layered or veined (crack fill)?

Do you remember the time when we didn't know at which side of the planet to look at since two rovers were discovering new things? This time's back

as well as weathered material on the surface redistributed as impact ejecta. This material could have been recycled for aeons, and created under several different climate conditions. Mindbogglingly complex.

--Bill

Ultimate origin(s) of the material may be too much to expect. We have to work backward from the way it looks now and how it fits into its context. I'd like to try out a rather simplistic hypothesis, namely that it is the remains of a continuous and widespread bed of sediment that formed in situ at some time between the Miyamoto and Endeavour impacts. How would it have responded to the latter? Given its softness and fine texture plus the possibility that it held water, I think it would have squidged and flowed all over the place as the Endeavour rim settled, destroying evidence of its original bedding and occupying cracks in the more resistant rocks. To a first approximation that seems to fit the scene we're looking at.

Yes, and what's better : there is TWO generations of rover on Mars. Working. We're living blissed times.

With all hypotheses I think we need to keep the big picture context in mind. The original impact would possibly have been large enough to create a complex crater. In support of this, the series of interior ridges within the rim to the east could be the remnants of marginal collapse zones. If so, then if CY is indeed part of the outer uplift rim the original surface would have been subject to surface spalling as well as horrendous heat, overpressure and wind scour. I don’t think a sedimentary deposit would survive in the way you suggest and I feel it more likely to be due to post impact weathering.

We're not looking at the original surface of the interior of the crater but something that has eroded outward a bit from there. What do you think would have happened to previously existing sedimentary layers a little distance out? At least we can say that layering is preserved here - the new spherule layer is still in place and it must have predated the crater. So I think you're wrong (until more evidence turns up). But thanks for responding to my suggestion!

Not necessarily, that depends on the final determination of the nature of the spherule layer and currently all is conjecture. Emily raised a good point that the crater would have eroded back to some degree, but the hills to the south seem to be remnants of the rim and CY is on the same circumference. So it was likely once internal to the crater rim, which would have been uplift covered by ejecta/suevite.

I really want to understand what you're saying, but this bit defeats me:


Anyhow on the 'conjecture' point I totally agree - there are many very different plausible scenarios given the huge depth of geologic time here.

Enhanced view of latest "Whitewater Lake" RAT activity...


Click to view attachment

That's kind of artistic looking.

At this point any of several puzzle-pieces can easily fit into the spaces allotted. That is why it is necessary to understand the lithologies (and depositional environments) above and below: ie, within the entire section. We're out of the Pottsville (Burns) Formation now, and things are getting more complex. On those two HiRISE images of this area that you and I posted there can be seen accessible outcrops higher and lower iin the section.

Without stratigraphy, geology would have nothing to sit upon; and without geology, geography would have nothing to sit upon. And so it goes...

--Bill

A.J. S. Rayl monthly MER update now available at The Planetary Society Blog...

Mars Exploration Rovers Update: Opportunity Finds Thrill of Newberries on Matijevic Hill
http://www.planetary.org/explore/space-top...newberries.html

Have not had time to read it yet....

Craig

A bit of a bump on 3090 to continue working on Whitewater Lake by the looks of it:
http://qt.exploratorium.edu/mars/opportuni...0M1.JPG?sol3090

"Mars Exploration Rovers Update: Opportunity Finds Thrill of Newberries on Matijevic Hill"

...a nice convoluted rock and roll pun....