[X] My Assistant

[Zeke4ther]

EGD, I think you might lose that bet.

I am betting this is not hematite simply because these are hollow spherules; and all of the broken hematite spherules we have seen in the past have been solid.

[CosmicRocker]

... is this a view of the outcrop from the Sol 2751 position?

I'm not convinced that the current outcrops were visible from the sol 2751 position.

Just to echo the sentiments of others, seeing these ancient rocks from the early days of the inner solar system's formation is incredibly fascinating. I've long wondered what the rocks from the bombardment phase looked like. Now, we may be getting to see them for the first time.

[serpens]

I've long wondered what the rocks from the bombardment phase looked like.

Welcome to the Hadean.

[Antonb]

This rather nice photo shows "a close-up of a partially devitrified black obsidian from the island Lipari, Italy, with lots of small spherulites in it" that to me at least show similar internal structure to the objects found by Oppy. See the section on "Spherulites and Wall-lining Banding" on this page for details on the growth of spherulites.

[xflare]

wow, some of those look very similar to the "spherules" in this Oppy image

http://qt.exploratorium.edu/mars/opportuni...M5P2935M2M3.JPG

[Bill Harris]

Welcome to the Hadean.

I can barely comprehend the conditions in the vicinity of a large impact. Can you imagine what it was like here at the time of the Miyamoto impact? "Plinian" would seem mild in comparison.

--Bill

[tdemko]

I'm waiting for tdemko to weigh in. I see several "sedimentary" structures that are taunting me. Something has happened there.

Well, since you asked...!

I'm going to have to go with ElkGroveDan's bet and say that I think that these spherules are the same type concretions that have been encountered in the younger, sulphate-bearing units at Meridiani. A while ago, I posted a summary of what the various stratigraphic and stratal geometric relationships between the units at Cape York that could be imaged by MRO, before Opportunity arrived there. As has been illustrated in the published papers, in general, the concretion-bearing sulphate strata onlap the impact-deformed older strata at the crater rim. The crater rim strata were a positive topographic feature throughout the initial time of deposition, and presumably, were eventually buried. This resulted in the apparent angular unconformity we see right now. The surface of the unconformity, however, seems to be quite complicated, which probably should be expected. Not only did it experience impacted related phenomena and ejecta deposition, but also weathering and colluvial deposition pre- and during the Meridiani "transgression" (or glacial advance, depending on your interpretation!). I think right now Opportunity is seeing some of the colluvial and initial Meridiani units in an angular, unconformable relationship with the tilted older strata. The same diagenetic phenomena that created the hematite spherules in the Meridiani strata would also have affected the immediately underlying deformed strata. Unconformities almost always are also boundaries important to subsurface fluid flow (aquacludes/barriers and aquitards/baffles), and can show distinct features reflecting perching/ponding of fluids and/or concentration gradients. The underlying deformed strata likely had zones or units of differing porosity and permeability, as well as original compositional and textural differences. The fluids that created the ubiquitous hematite spherules in the sulphate units must have also diagenetically altered the units at and below the unconformity.

[centsworth_II]

....The fluids that created the ubiquitous hematite spherules in the sulphate units must have also diagenetically altered the units at and below the unconformity.

Ah! That lit a light for me!

I was thinking that if the matrix was not the same sulfate sandstone that the hematite concretions formed in, that the sphereules could not be the same hematite concretions. But now I see that the same groundwater which formed the concretions in the Meridiani sulphate layers would have permeated and perhaps formed the same concretions in Endeavour's rim material. Thanks for the illumination.

[Bill Harris]

Hi, Tim. So you think that the spherules are just the hematite concretions? Good possibilty. But we'll examine more examples and decide why they (apparently) have a different internal structure and why they (apparently) weather differenly. More color Pancams up today, she'd preparing to RAT/Brush and part of The Outcrop With No Name has been tagged "Kirkwood", P2560.

This is complicated. If we were there, we'd all be at the outcrop flat on our bellies with handlens, brush and hammer busy.

--Bill

[fredk]

they (apparently) have a different internal structure

We've seen blueberries split in half, and IIRC they looked something similar to what we're seeing now. Unfortunately I can't recall the sols... Did you have particular old blueberry MIs in mind, Bill?

[Bill Harris]

Oh, my there are about a gazillon MIs to look through. Seems like they were earlyish MIs, like pre-Purgatory. They were "similar"-- rind and core, but maybe I think "different" because Hope Springs Eternal. These "seem" to have a more pronounced internal structure, but remember, the wind in this vicinity is strong and persistent enough to keep the pavement down on the bench swept clean and this outcrop uncovered, so the internal structure may be visible due to unusual aeolian erosion.

We'll be seeing a LOT more on the next few days.

--Bill

[ngunn]

These appear very different from the blubes we're accustomed to seeing.

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

That was three days ago. So are we still missing the R5s? I thought we'd have this nailed by now.

[serpens]

R pancam aside, the L257 don't have the same response as the hematite concretions, so if they are concretions there are differences in makeup. The lack of blubes on the top of CY would seem to imply that it was not overrun by the Burnes materiel so if they are concretions (not necessarily hematite) then this implies significant groundwater at the inner rim of the crater with the consequent implication of a lot of water within the crater. (Also indicated by the response of the fill that over-ran the NW crater wall).

I think that identification of the matrix materiel will be a key factor in determining the provenance of these spherules but I think I will tend towards a cluster of impact related spherules/lapilli. While we have seen a few hollow, split blueberries on the plains these have been few and far between and we haven't seen anything like this outcrop before. The 'junk' that dburt drew attention to could possibly be clasts ripped up in a ground surge rather than concretion nucleation sites but as Bill Harris said, these examples have been subjected to long, slow erosion. Preferential erosion seems more likely in lapilli than concretions. Roll on the APXS

[Gladstoner]

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[charborob]

I thought they were calling the whole area Fin Ridge

This part of the outcrop does look like a fin. Funny weathering anyway.

This anaglyph might be a bit difficult to view, because the "fin" is just on the edge of the pancam images.