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Concepción, The freshest crater yet to be explored
Stu
post Feb 11 2010, 04:38 PM
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Mosaic of some new MIs...

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eoincampbell
post Feb 11 2010, 05:18 PM
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Wow, the blueberries seem to be really concentrated though still embedded... a heavier cluster than any berry bowl we've seen ?


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Stu
post Feb 11 2010, 06:03 PM
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Easy to imagine actually standing there, next to these rocks, when you see a view like this...

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MarkG
post Feb 11 2010, 06:18 PM
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...The anatomy of a crack, and a very dirty one. Likely a result of dessication shrinkage and debris (mostly blueberries, plus general Martian dust) filling, with evidence of multiple episodes of some sort of degree of re-hydration cementing things a bit.
We see again how the passage of time preferentially concentrates the hematite nodules while the sulfur-salt-sandstone matrix is powdered and blown away.
The extreme friability and tiny particle size of debris powder of the Meridiani substrate create some interesting questions. We have seen dunes of the sulfur-salt stuff only on places like the rim of Victoria, where the rate of production and concentration of the sulfur-salt powder is relatively prodigious. Where does it go? Some ideas...
1) The Meridiani hematitie/sulfur-salt plains occur only on a small percentage of the surface of Mars. Its eroded dust thus becomes just a trace constituent of the general Martian dust. It is just diluted to near-invisibility.
2) The sulfur-salt dust could be a preferred nucleation site for precipitation. Snow nucleus. This would systematically remove it from the global dust inventory over time.
3) There could be some sort of very slow chemistry going on between these sulfur salts and the Martian atmosphere. This might also influence how it erodes. It could be driven by some trace atmospheric constituent or even solar/cosmic radiation side effects.

Anyhow, these are some thoughts that the Concepcion MI's have brought to mind. I don't have good access to journals (I do read articles I find out about, by the way) or daily bull sessions with grad students, or full access to all the results of the instrumentation, so maybe this has been covered already. This forum is my scientific coffee break, about all I have time for. I hope the working scientists don't take offense, and will be glad for the display of interest in the details of their work, and forgive the speculations-based-on-inadequate-data that come out of this forum.
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Tman
post Feb 11 2010, 06:21 PM
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QUOTE (Stu @ Feb 11 2010, 05:38 PM) *
Mosaic of some new MIs...

yummy...baked blueberries?


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Stu
post Feb 11 2010, 09:52 PM
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Introducing the new "Chocolate Hills" bar... crammed full of tasty berries and covered in a delicious, dark crunchy coating...

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fredk
post Feb 11 2010, 10:46 PM
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Rightmost block of Chocolate Hills as pancam anaglyph:
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Nprev, with some luck I may be able to coerce the Mystery Men to come out of hiding - they're remarkably shy, but all this talk of chocolate may help...
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ngunn
post Feb 11 2010, 10:52 PM
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I love the way the random polygons on that rock fit themselves into a square. It reminds me of this:

http://images.google.co.uk/imgres?imgurl=h...t%3D36%26um%3D1
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Shaka
post Feb 12 2010, 12:29 AM
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Hmmm....verrrry interesting.
Is this the first time we have seen blueberries so tightly packed within a lithifying (?) matrix? Most of the laminated sandstone around here has the concretions well and evenly spaced, as in the usual pattern of their in situ formation. I assume they cannot form in such a closely-packed pattern, so we must infer that they were eroded out of the laminated sandstone, collected together in a crack between blocks and then re-cemented by later fluid invasion of the crack. Is this final step a rare and localized event, such that we have not seen before on Meridiani? Does this region have an unusually lengthened diagenetic history? One which points to a wet period following blueberry formation and excavation? Some areas of the exposure seem to show where blueberries have fallen out, leaving an "egg-carton" like pattern in the matrix. Blueberries excavated for the second time in their 'lives'! How long was this part of Meridiani wet?

Always something new. smile.gif

EDIT: Or could the local impact have played a role? C'mon, Don, are you taking the plunge? cool.gif


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centsworth_II
post Feb 12 2010, 12:56 AM
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If those are remnants of a fracture fill on the surface of the rock, maybe it was a fracture filled with loose berries which were then lithified by the fill material.

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Shaka
post Feb 12 2010, 01:55 AM
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I'd say that's the most parsimonious explanation, $.02, (Don might disagree), but then why haven't we seen it before?
Could the crater here provide a more localized, recent mechanism to 'cement' the concretions?


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fredk
post Feb 12 2010, 02:52 AM
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In the latest update, they still refer to impact melt:
QUOTE
This rock target is of interest because it exhibits a dark rind or crust that may be impact melt.
But INAG (I'm not a geologist)...
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dburt
post Feb 12 2010, 04:34 AM
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QUOTE (Shaka @ Feb 11 2010, 05:29 PM) *
Hmmm....verrrry interesting.
...How long was this part of Meridiani wet?
...Or could the local impact have played a role? C'mon, Don, are you taking the plunge? cool.gif


I'd hesitate to rule out a role for impact being so close to the little crater, but probably not, other than excavation. "Wet" is a relative term, so a possible working hypothesis might involve the role of soluble salts plus fallen dust plus transient moisture/frost in creating a cement to hold the fallen berries together within an initially open fracture, before impact exposed the sample. That potentially gives us billions of years of daily and seasonal and epochal climate change to call upon to cement the berries, without having to call upon flowing or standing water, other than transient surface films. (Or impact; sorry, I didn't even stick my little toe in...)

Just an initial working hypothesis, of course. One possibility among many, including impact melting, especially given that moist salt mixtures must have quite low melting temperatures (i.e., be very easy to fuse into a cement). On the other side, if the rock were exposed to enough impact stress to fuse the salts, how on Mars did all the brittle berries survive intact? So I'd tentatively rule out impact.

I'd tentatively rule out large quantities of liquid water too, because everything remains so fine-grained. If salty water were standing or flowing in that crack for any length of time, we might expect to see visible salt crystals (or their ghostly imprints) lining it, or perhaps solution/recrystallization damage (i.e., disaggregation) or other visible alteration affecting the salty rock next to the crack. (Where salts are concerned, liquid water is powerful stuff!) Such evidence appears to be lacking.

That seems to leave a crack filled with fallen berries and salty dust and frost and transient moisture and time as the least unattractive hypothesis for cementation. So boring!!

--HDP Don
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centsworth_II
post Feb 12 2010, 05:00 AM
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QUOTE (dburt @ Feb 11 2010, 11:34 PM) *
...if the rock were exposed to enough impact stress to fuse the salts, how on Mars did all the brittle berries survive intact?...
I was under the impression that the berries were not so brittle, especially when compared to the sulfate rock. I find it hard to imagine blocks of that fragile material traumatized enough to melt the surface while the block remains intact. Especially so close to the rim of such a small crater. This looks like a big thunk and a lot of little thuds.

It seems a bit of a knife edge to define an impact that would leave such a small crater and melt the surface of fragile sulfate ejecta blocks while leaving them intact, and not throwing them very far.
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Shaka
post Feb 12 2010, 05:17 AM
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AHAAA! The penny drops...
The dollar drops...
The euro rises...
The moon is blue and Prof Don favors moist chemistry, whereas JPL favors "impact melt". blink.gif
...anyway, Shall we then follow our JPL PI's and view the 'matrix' as the product of molten or vaporized impact material injected under high pressure into cracks in the bedrock, engulfing and entombing the berries within? Why haven't we seen it around any of the other craters we have surveyed? Is it a very short-lived material like a glass, which breaks down quickly ( i.e. in thousands rather than millions of years)? Should it have an exotic - partly extraterrestrial (Mars equivalent) - composition, which we can detect with the IDD? Can we see any other signs of this violent history? On the other hand, this IS a crater and there must be some violence involved!

Is Mars boring? Noooooo! biggrin.gif





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