To explain my understanding, I've matched a geologic map of Merridiani (from here) with the corresponding area from Google Mars. Endeavour crater (red arrow) is buried in Meridiani deposits and subdued compared to the craters (yellow arrows) outside of the area of the layered deposits. The craters near the edge of the deposits (blue arrows) are special cases. I don't know if they were never fully covered, have been almost fully uncovered, or punched through the deposits. The smaller (blue arrow) crater near Endeavour is Lazu.

From these images -- and many other papers on Meridiani -- it is clear that Endeavor and its ejecta is buried in up to hundreds of meters of Meridiani deposits. The only visible part of the original crater are the rim peaks (including Cape York!).
Click to view attachment
Some quotes from the paper:
"We have completed a regional analysis of the hematite deposit in Terra Meridiani and
conclude that the unit is in the midst of a 600-m-thick stack of friable layered materials
superposed on Middle and Late Noachian cratered terrain."

"The hematite (P2) is in the midst of a complex stratigraphic sequence of layered materials. These younger
layered deposits (P1, P2, P3, E, I) are superposed on ancient cratered terrain..."

"The layered deposits clearly bury the underlying cratered terrain..."

Cant recall where but i had read that there was a possibility that the water activity in meridiani could be related to lava coming into contact with ice underground when the tharsis bulge was forming... meridiani lies on a slope from the tharsis bulge and mariner valley is close by!

.

I don't see any reason to invoke a significant ejecta layer on top of the Meridiani sulfates near Cape York. The only places we've seen significant ejecta have been very close to the individual craters that created the ejecta, and there are no large craters near Cape York that post-date the Meridiani sediments. The surface bedrock here does look kinda broken up, but that could be due to the ubiquitous shrinkage fracturing that we've always seen, coupled with downslope movement and settling stresses associated with being draped over the Endeavour rim.

John

.

The ejecta from that crater would be *under* the Meridiani sediments, as it pre-dates them. We might see some sign of it on Cape York, though...

John

.

It seems that Endeavor was created before most (if not all) of the Meridiani sediments were emplaced. The sections of exposed rim of Endeavor are essentially ejecta from the Endeavor impact. After that impact, the Meridiani sediments were laid down, perhaps with rounds of erosion in between. Did the raised rim sections get buried/eroded? Cape York sure looks like a piece of the rim that was long ago buried, and now is being exhumed. Other higher parts of the rim may or may not have been buried. Were these "islands" eroded by wind? water? ice? brine slime?
Note the Endeavor central plateau, with hundreds of meters of sediment, worn away most just inside the rim. It is amazing what can happen slowly if you've got a couple billion years...
I've noticed that the sediment layering partially follows the slope -- not sure without better analysis. It is possible that the circumferential "zones" around Cape York may be more chemical in nature than structural. I.e, just different strength and chemistry of the matrix just due to original ionic groundwater diffusion from the older rim ejecta. We will soon see.
I'm having great fun thinking about it all.

.

Unfortunately almost all analysis published is concentrated on a small section of the western rim and the big picture of Endeavour and surrounds seems to receive little attention - or I may have missed the published data? With the exception of a couple of meteorites designated as having a Martian origin the ejecta we have passed has been displaced Meridiani sediment and the blocky ejecta just ahead will hopefully be our first opportunity to sample the ancient bedrock. The sediments have over-run the NW crater rim and part filled the crater so the original surface and overlaying Endeavour ejecta should be well buried, as John pointed out. The hematite response mapping indicates a high concentration inside the crater which would indicate that the mound is the ubiquitous cemented sulphates and that the crater has had significant water influence. But the mapping scale doesn't provide much discrimination.

Now that we can get a good look at the rim it seems well eroded. Is it ejecta or uplifted / overturned bedrock? The sediments seem to onlap the westerly side of the rim rather than being covered by material eroding from the rim and it would appear that there has been little erosion of the rim material since the sediments were laid down. So I tend to think that Mark's chemical alteration hypothesis for the terraces looks pretty good. We'll soon find out as Opportunity can now get back to being a geologist rather than a tourist.

Agreed, Serpens.

At this point we can see as much sitting a few meters from the contact as we have seen a few kilometers above the site. We'll know more next week when we do get to the contact, but for the time being, closely evaluating this transition zone is important. We'll know more when we know it.

I think the basic scenario here is simple. Endeavour crater was created on the basaltic basement and is unconformably overlain by the later aeolian/lacustrine (or, more properly, "playan") sediments of the Burns Fm. At this time, we don't know what the paleo-surface of the was like, nor what the many depositional or erosional environments that occurred over the billions of years between the "Endeavour Age" and the "Burns Age" are like. I feel certain that the CRISM phyllosilicate signature(s) are from an old weathering surface on the upturned basalt of the Endeavour rim, and more specifically, the nearby phyllo-signature is from weathered and covered ejecta from a crater in this weathering surface on the Cape York crest.

Who knows, it may even be the "Betty Bluep" rocks we saw at Sata Maria or the elusive "5YR 4/3 outcrop" brown argillageous-looking outcrop we've seen along the way.

These are interesting times...

--Bill

While it is generally accepted that vast amounts of erosion of sediments over broad areas of the highlands has produced crater "mound" remnants like those in Endeavour, it isn't really true that sedimentary deposits are always deposited horizontally and continuously to their maximum elevation over a region.

The martian polar layered deposits are a good, familiar example of a subaerial deposit that is thick but never (likely) extended across the northern plains to the elevation of their summit. The layers are also not horizontal.

The Bahamas are an excellent, familiar example of a subaqueous deposit that is kilometers thick but never extended across the Atlantic Ocean basin.

Once again, however, many on the MER project accept the model of extensive erosion of the Meridiani Planum sulfates.

It will be interesting to see if there are blueberries on Cape York, indeed. If there aren't, it might suggest that Cape York was never buried by sulfates. But it also might be possible that the geochemistry of the groundwater within the rim rocks wasn't conducive to hematite concretion formation.

It's a hypothesis!

-Tim.

One thing evident from the pictures of Cape York is a zone of "reduced topography" inside of, but concentric to, its boundary. One can speculate that this represents a "zone of alteration" of the original rim deposits after burial by the sulfate sediments.
The Odyssey crater is centered on the inner boundary of this zone, and indeed the northeast half of the rim debris is made up of larger (stronger) rocks, while the southeast half has almost no large rocks, presumably because the zone-of-alteration made debris from that side more friable.
It is also possible that this zone represents an ancient soil layer in the rim deposits, and that role, rather than alteration by the subsequent Meridiani sulfates, made them more friable.
The presence of obvious intrusive veins in the rocks currently under Oppy is another constraint on understanding things. Do the big rocks on the other side of Odyssey contain such veins?
The remainder of Oppy's scientific functionality will be well-challenged to answer these questions. But we are indeed positioned to ask them.

(edit: thinking ahead) Perhaps a spot can be found to park Oppy for the winter and point mini-TES at something interesting for a long time?

It's not integration time that's the problem. It's just contamination. It can't see out. It's filthy.

Mossbauer, on the other hand - that's just an integration time problem....so many weeks might be necessary.

As kenny noted on August 14 in the Cape York thread, some of the large boulders may have split along veins. We now see Tisdale and at least one boulder east of it with a surface that may be what's left of veins they split along. So, pending confirmation that the light boulder surfaces are in fact equivalent to the veins in the ground, observations east of Odyssey to date are consistent with an answer of "yes".

On sol 2748 a series of subframe images described as pancam_foreground were taken. Attached is an L456 false color composite from that series. I don't think we can say we see blueberries with certainty from this single image, but several of the pebbles in this image appear to be quite spherical and have approximately the right color to be the concretions.
Click to view attachment
Unfortunately, the R5 image has a large data dropout in the critical area, otherwise I could make a right filter, false color composite that could unambiguously identify hematite. I'll watch for the full R5 image to come down and will post the right filter composite when it does.

Try L257 and R721 images for this.

In this image set I've seen several nice rounded pebbles, but none that seemed unambigiously Blueberry-ish.

We'll keep looking.

--Bill




PS-- I was going to put these on the Photobucket site tomorrow AM, but I decided to do 'em tonight.

http://i142.photobucket.com/albums/r91/wil...00P2559L2M1.jpg

http://i142.photobucket.com/albums/r91/wil...00P2559R7M1.jpg

--b

Good idea. I'll get things moved.

--Bill

Topic split as requested - Image Enhancement for Mineral Identification - Moderator

I think you split the posts at the wrong place. My original observation that blueberries may have been observed in the sol 2748 pancam_foreground images is highly relevant to the discussion of Cape York's geomorphology.

A couple of posts moved back - Mod

Many thanks, anonymous Mod.

I'd like to follow up on my earlier observation about possible blueberries (hematite concretions) in pancam images from sol 2748 on Cape York. It had been suggested that if a residuum of such concretions would be found on top of the very different geologic bedrock of Cape York, it might mean that the cape had previously been buried by the blueberry containing sulfate sandstone that covers Meridiani Planum.

Since the target was imaged with a full set of infrared filters, we can make a false color image based on pancam right filter ratios that has successfully identified hematite in the past. In such false color images hematite typically appears in shades of yellow or orange. Some of us briefly discussed this image processing in another part of the forum.

Getting to the bottom line, the processed image showed plenty of hematite in the ground Opportunity is driving over. There were numerous spherical hematite concretions as well as angular fragments of hematite visible in the image. The question now becomes, How did this hematite arrive on top of Cape York? It seems to me that there are three alternatives:

1: It dropped down onto the basement rocks as a lag deposit as overlying sulfate sands were eroded away.
2: The concretions and fragments were transported to their current location by wind or water currents from the surrounding plains.
3: They were thrown onto the cape by meteorite impacts on the plains.

I think it may be difficult to distinguish among the alternatives. Are there other alternatives that I missed? I would have liked to provide a thumbnail link to the above image, but I still have not figured out how to do that without uploading the whole file again.

4: Condensation lapilli (distinct from your no. 3, I think)

Disclaimer: doesn't mean I believe this, just that if we're brainstorming upon finding the things in an unepected location nothing should be dismissed.

I see angular and rounded pebbles with a "hematite signature" but not to the extent that I can call them "blueberries". We've not seen these rounded pebbles in-situ, nor broken in x-section, so I can say that they are blue, but can't say berries.

And, as Nigel suggests, they may be lapilli. One characteristic of this region of Mars is the abundance of various Iron (III) oxides and hydroxides. And we don't have much experieces locally with hematites as impact melts.

The western slope of CY is so shallow that some "onlap encroachment" is indeed possible, especially at this highly-eroded point on the Endeavour rim. So a blueberry or two wouldn't be earthshaking. Those clasts do simply _look_ rounded, and not necessarily blueberrish. So the jury will be out til we get more mineralogical data.

--Bill

I understand what you are saying, Bill. It would be nice to see these pebbles on the surface rather than embedded in the soil, and a x-section would be the icing on the cake. A wheel scuff to dig a few of them up would help a lot. However, I don't think it is such a stretch to imagine that the most obviously round ones are truly spherical and not simply pebbles rounded by erosion. If you can imagine that, and accept the evidence that these things are indeed hematite, it is simpler to assume the spherical pieces of hematite are the same ones we've been seeing all these many years through Opportunity's eyes, rather than assuming some other origin for them.

This is really an interesting soil image. The abundant, angular pieces of hematite are very curious. We have rarely seen gravel composed mostly of hematite and with a large population of angular fragments. It looks like a bimodally sorted size distribution and perhaps a bimodal shape distribution as well. I'm not sure what that means, but it could possibly be evidence of a very different transportation mechanism than we have normally observed for the hematite fragments. If I had to guess, I'd suspect a higher energy environment.

Over the years, there have been many discussions of "shorelines" as theoretical possibilities or dry analogs.

Could we be for the first time approaching an actual ancient shoreline? How would that confirmation happen?