Farewell Beacon..., The next cape beckons... Options

[Shaka]

Wow! If I live to be a hundred, I'll never understand why we've sailed right on past the Beacon toward "Boat Ramp". I agree that the deepest exposures are the most important, but Beacon is the highest! It's sitting right there waiting for us. It's the top of the section. Whether it's composed of impact breccia or undisturbed laminated evaporite determines whether Victoria formed after or before the deposition of the upper Planitia Meridiani. I can't believe that is a trivial issue. It is a fundamental fact of Victoria's history.

[CosmicRocker]

Shaka: I'll have to admit that I too was a bit surprised that they left the area so quickly, but it is true that they have a lot more spectral information on the rocks than we do at this point. I think we might be able to get a clue though, from the MIs taken of the RAT hole on Cape Verde. Granted, CSM is higher stratigraphically, but not that much. The MIs displayed several large berries embedded in the rock and shaved by the RAT. They are pretty confident in their model of these concretions having formed in sediment saturated by ground water, or what is usually called the phreatic zone. On the trip south Opportunity climbed stratigraphically and observed no berries and micro-berries at the highest points, which is consistent with that model.

The fact that they discovered large, embedded concretions in the rock here might suggest that these rocks came from the section that we have already seen. I must point out a serious flaw in this argument before someone else does. You would expect the surface rocks there to be ejecta, so they likely were derived from deeper layers. But now that I think about it, perhaps a better argument fro leaving would be that it appears that CSM is also mantled in ejecta, so what is the point of wasting time there? Better to move on and learn more about deeper, intact layers.

Jeff7: Some of us think those dark streaks were formed by the removal of light colored dust rather than dark dust deposition. So, it may be a good place to go for Opportunity's solar panels. I hope we can observe something on the soil as Opportunity passes bay B1, to allow us to determine whether the streaks are due to erosion or deposition.

As long as I am going off topic, here is the drive direction panorama from sol 1009, as I was able to stitch it.

[Shaka]

Granted, CSM is higher stratigraphically, but not that much.

This is true, of course, Tom, but why not grab the very top of the section when it's sitting there waiting for you to RAT it. And we have risk-free access to the exposed edge of the layer, as well as the top, without having to reach over the brink and risk a tumble down to the dunes. If the edge reveals laminae, and there is no discontinuity with the underlying layers, we have strong evidence that the beacon is in situ, and therefore points directly at an ancient (Noachian/Hesperian) formation of Victoria, followed by burial and recent exhumation.

The MIs displayed several large berries embedded in the rock and shaved by the RAT. They are pretty confident in their model of these concretions having formed in sediment saturated by ground water, or what is usually called the phreatic zone. On the trip south Opportunity climbed stratigraphically and observed no berries and micro-berries at the highest points, which is consistent with that model.

But if the evaporite is in situ, then it indicates that ground water existed both below and above the berry-free strata.

The fact that they discovered large, embedded concretions in the rock here might suggest that these rocks came from the section that we have already seen. I must point out a serious flaw in this argument before someone else does. You would expect the surface rocks there to be ejecta, so they likely were derived from deeper layers. But now that I think about it, perhaps a better argument fro leaving would be that it appears that CSM is also mantled in ejecta, so what is the point of wasting time there? Better to move on and learn more about deeper, intact layers.

But Tom, those of us in the "Ancient Victoria" school of thought, don't believe that we are seeing, driving over, or ratting Victoria's ejecta. We hold that ejecta is nowhere to be seen. What we are seeing is sandstone that roofed over Victoria back in the Noachian/Hesperian, was subsequently indurated and leached by ground water to produce concretions, and finally eroded and collapsed.

I am frantically awaiting close-up views of the uppermost exposures in the capes to see if they are primarily intact, in situ, more or less horizontal sandstones. The latest pancam of "Hoy" looks remarkably in situ right to the top. If close examination confirms this all around Vikky, then I will hold my hypothesis to be supported. I cannot emphasize too strongly that a hypervelocity impact shatters the target rocks near the crater, transforms some into exotic forms, hurls them high into the air and deposits them around the crater with a more or less random orientation of chunks (OK, clasts) in an impact breccia. We saw some of this around Beagle, though that was such a tiny crater that regular impact models may apply imperfectly.
I have not yet seen anything around Victoria that I would call impact breccia. Close-up views may reveal it, if we ever get any. Hence my disappointment when Beacon was bypassed.

Jeff7: Some of us think those dark streaks were formed by the removal of light colored dust rather than dark dust deposition. So, it may be a good place to go for Opportunity's solar panels. I hope we can observe something on the soil as Opportunity passes bay B1, to allow us to determine whether the streaks are due to erosion or deposition.

I agree with you on this. I don't see any source of dark material down in Vikky. The only dark things in this area are the concretions, perhaps, and the basalt sand grains when they are cleaned of dust. It depends upon lighting and viewing angles, of course, but in general, what looks darker on Mars is more dust-free.

As long as I am going off topic, here is the drive direction panorama from sol 1009, as I was able to stitch it.

Yeah, I'll let other, more tidy minds decide whether to leave these posts here, or put them in the stratigraphy thread.