On the Road Again - volume 5 - Page 14

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Serpens


Posts: 169

Reply: 261



PostPosted: February 22, 2010 4:30 AM 

Hortonheardawho. I think Ben's model is reasonably sustainable - apart from the layer and berry formation being concurrent. Doesn't the geochemistry indicate that that the lithification process here was cementation with authigenesis? There is no indication of metamorphism. So overburden requirements would be nil, other than ripples or shallow surface liquid depositing the
layers. We saw clear evidence of deflation and deposition cycles in the Victoria cliffs, but I thought that JPL had estimated only 1 or 2 meters deflation in this cycle?

I would think that the erosional mechanism in this area since the impact event is more due to suspension than saltation. Very gentle but obviously effective over a long period due to the fragile nature of the rock. Gentle eoloian erosion, a geologically benign low gravity environment and voila: berries on stalks.

False color imaging seems to indicate that the fracture fill has a hematite content.
We also have empirical evidence from Cape Verde that fracture fill can go deep, but how deep is an unknown. Width? Well we have seen the extent to which dessication cracking separates the edges of a fracture.

John


Posts: xxx

Reply: 262



PostPosted: February 22, 2010 7:11 AM 

Thinking about these dessication cracks. There are locations we have seen that indicate material is dropping down these cracks. In addition to many raised pavement blocks. Seems like a pretty dynamic process is ongoing here. How did the fracture fill become laminated? I think about the great cracks that occur in my yard every summer. They are about an inch wide and very deep. (Yeah, I dropped a fishing line and sinker in one.) Come winter, they are gone, but show up in the same places in summer.

Barsoomer


Posts: 344

Reply: 263



PostPosted: February 22, 2010 11:21 AM 

> reasonably sustainable - apart from the layer and berry formation being concurrent

So Serpens, you disagree with Ben on this aspect of the model? Is that correct? But he uses this mechanism to explain some of the morphology of the stems. Can you suggest an alternative for the morphology under your interpretation, or do you dispute the observation, or do you just see this as a weakness of the model?

Barsoomer


Posts: 344

Reply: 264



PostPosted: February 22, 2010 11:28 AM 

Just to make my previous post a little clearer, I believe Ben used the concurrency to explain the association of the berries and stems with the more resistant bedding planes, and a preferential orientation of the curved stems. Perhaps Ben can correct me if I can getting this wrong.

Bill Harris


Posts: 72

Reply: 265



PostPosted: February 22, 2010 11:30 AM 

Hort exhorted:

Again I think the best way to proceed is develop a parameterized geological model ( your job rock guys ) and demonstrate that some observations fall outside the boundaries of the model.

Good idea. To develop a "parameterized model" one needs, uh, parameters. The overwhelming source of data here is from images. So we should pass the task of analyzing and collecting photographic data to our resident imaging maven, Hort.

Start giving us numbers for the type of model you asked about, and we'll work on it. If we need additional numnbers, we'll be sure to ask you...

Bill Harris


Posts: 72

Reply: 266



PostPosted: February 22, 2010 11:43 AM 

Serpens:

"I think Ben's model is reasonably sustainable..."

I think it is too, for the most part, although there will always be minor divergences in opinions between professionals.

At least we using stromatolites in tropical seas to explain secondary features, or vulcan mind melds to illustrate impact melts. Rolling Eyes

The SE ejecta ray seems to have more blocks from the surface (ie, "pavement stones") as well as rocks from deeper areas.

--Bill

Bill Harris


Posts: 72

Reply: 267



PostPosted: February 22, 2010 11:48 AM 

"re your 174, It is good to see Dr Burt blogging again at UMSF"

Has Don Burt ever posted here? Wonder why not?

Barsoomer


Posts: 344

Reply: 268



PostPosted: February 22, 2010 12:19 PM 

> Gentle eoloian erosion, a geologically benign low gravity environment and voila: berries on stalks.

There is one thing that puzzles me about this scenario. Why are the berries on stalks far more prevalent at this crater than at the many other craters that Oppy has encountered? While it may be arguable how young the crater is, it seems clear that most of the other craters we have seen are far older.

If the delicately sculpted stems and lattice that we saw on Porcupine rock are indeed carved by the wind, I would think we would want some MIs for the geology textbooks, since I think this would be a wonder beyond what we see in wind sculpture on Earth.

Kye Goodwin


Posts: 1166

Reply: 269



PostPosted: February 22, 2010 1:12 PM 

Bill Harris, I'm not going to try to find it right now (I've lost a lot of internet "Bookmarks" to computer failure ), but Don Burt did publish a paper with our contributor Dennis in which he credited this MARS ROVER BLOG as the forum where many of the ideas in the paper were first discussed. It was among the LPSC abstracts last year or the year before and dealt with statistically characterizing spherule distributions on soil.
I think that UMSF is a higher profile forum than ours, and also much more resistant to the impact sediment explanation of Meridiani and HomePlate. I think that it is great that Dr Burt continues to contribute even under Doug's GAG ORDER , because it might strike many people as very strange that a hypothesis that was published in the journal Nature is being actively suppressed. It can't be because the idea is too flakey, obviously, so it must be an idea that is too dangerous.

Ben


Posts: 2270

Reply: 270



PostPosted: February 22, 2010 1:20 PM 

Bill and Serpens; Thanks for picking up the slack. I was getting spread pretty thin with other things I am involved in.

The reason I dwell on stems,hard layers etc. is because I believe the berries started as air-fall pellets from storms but not surge related.
The fact that the berries are located in the resistant layers leads me to believe this is a cyclic phenomena( maybe like storms seperated by thousands of years).

I am particularly intrigued by the indications that the softer layers support no stems which one would expect due to the material involved.

As you mention Serpen , it is very clear that minimum erosion shown at this younger crater is very different from the others we have seen .

One last comment about the field of Geology.
"Our government does not include geology
in the list of Physical Sciences which include Chemistry, Biology, Physics,& Math.
Their explanation is that it is based primarily on logical interpretation of data that is quite variable.

GOOGLE "Laws of Geology"

Sorry if this diminishes our stature among you forum participants but all I can say is I have never met a Geologist who isn't
totally happy with their choice as a profession and their contribution to the welfare of mankind. Very Happy

Ben


Posts: 2270

Reply: 271



PostPosted: February 22, 2010 1:30 PM 

Don Burt; If you follow this forum I think I can say without contradiction, that we would welcome your participation in our discussions.

Don't be offended but I reserve Dr. for medical practioners. Very Happy

Barsoomer


Posts: 344

Reply: 272



PostPosted: February 22, 2010 3:17 PM 

After looking at several rocks, it appears to me that the crusty coating favors rocks that have strongly parallel grain or bedding, and disfavors rocks with complex irregular grain.

Bill Harris


Posts: 72

Reply: 273



PostPosted: February 22, 2010 4:46 PM 

I swear that they're sneaking images in behind our backs...

Pan-, Nav- and Hazcam images on the steam table at Exploratorium.

--Bill

Barsoomer


Posts: 344

Reply: 274



PostPosted: February 22, 2010 5:00 PM 

This rock seems to be eroding very rapidly. The fact that we still see it at all is suggestive of the youth of the crater.

This one seems to have an additional coating beyond the usual crusty one.

Barsoomer


Posts: 344

Reply: 275



PostPosted: February 22, 2010 5:24 PM 

Rock at bottom-right. Is this the kind of small wavy cross-bedding that is indicative of water action? The rock appears to have berries with tails. So in this case, are the "wind tails" more likely "water tails" that occurred when the sedimentary rock was forming?

LWS


Posts: 3062

Reply: 276



PostPosted: February 22, 2010 5:30 PM 

Hort, Ben, Serpens et al.

RE. my #257 last night. I've noticed that no one seems to have noticed the logic or illogic in. I've therefore tried to explain my thoughts with the graphic below

This graphic tries to isolate the rock(s) in question from the others in the image.

Last night when I made the comments I only noticed a matching rock after I posted #257. That possible matching rock has forced me to modify the suggestion I made.

I think the images are very important in understanding the nature of the changes to the rocks at impact and afterwards and the nature of the rocks before impact.

I think that these rocks supports Ben's speculation on water upwelling through crevices inter alia.

I think it is reasonable to assume that rock A cracked on impact; that it cracked along a pre existing fissure; and that the other portion of the rock on the other side of the fissure probably landed somewhere in the vicinity of the original rock.

The original rock shows a depression that can be seen in the anaglyph in diagram and in that depression some pieces of the "fill" or impact melt or crust can be seen. What is most noteworthy about rock A is that the crust seems to have extended over the lower edge of the depression.

The existence of the crust going over the edge of the depression fracture and apparently being continuous with the crust on the interior of the depression, along with the existence of small pieces of crust on the surface adjacent to the rock initially suggested to me that the crust must have "grown" after the impact as it seemed unlikely that the crust would have passed through the breakage in the rock as it split to be now seen at and below the edge.

The picture was complicated or perhaps simplified when I later looked at the rock in the foreground, B. It looks as if it might be a reasonable fit for the depression in rock A snd therefore might be the missing piece broken off that rock at impact.

If that is so, it lends some weight to the fracture fill hypothesis as it seems likely that what we are seeing from the depression and on the foreground is material from what might have been a fracture fill. However that material must have been relatively plastic at impact for the two sides of the rock to retain pieces of the fill. Also, the existence of "fill" on so many rocks and on so many sides of rocks is still problematic for the fracture fill hypothesis.

I would still wish to suggest that the images of the ubiquitous "fill" material continue to evoke comparisons to microbial mats and that there is still a possibility that underground crevices in these rocks, before the impact, provided environments where water films moved upward from a subsurface icy resevoir. Various organisms could have lived as microbial mats in this environment. The impact removed them from their natural environment, landed them on the surface and they became fossilized.

The crusts would therefore essentially be fossilized microbial tissues.

There are of course a number of predictive outcomes for this model. I'll try to detail some of these in another post.

I also think that these images continue to show signs that the impact event was a relatively recent occurence.


Winston

serpens


Posts: 169

Reply: 277



PostPosted: February 22, 2010 6:06 PM 

Ben, the reason I believe that your hypothesis of air-fall pellets covered by a shell following authigenesis does not hold is that pancam false color images of broken and ratted berry interiors show the same composition as the outside. Also wouldn't infrequent air-fall such as you describe result in concentration along bedding planes? There is no indication that berry formation was associated with any particular layer. Having said that, your hypothesis on stalks being a product of more strongly cemented layers makes perfect sense. Erosion results in a wind-tail in the berry lee on surfaces where windflow is parallel to the surface. But on a slope or face where the wind force is more perpendicular the erosion would form a stalk. The length of the stalk that eventuates would depend primarily on just how strongly cemented the material in the lee is.

As I understand it the purpose of the Drake equation was philosophical, designed to focus on the concept rather than provide a definitive result. With so many unknown variables the Drake equation result is in fact a scientific wild assed guess. We certainly should not apply that approach to the wealth information we have received from the MER. (Although JPL does seem to have become increasingly parsimonious over the release of data).

Barsoomer. Could it be that the complex irregular grain is where rock fractured violently on impact, whereas the fracture fill is along an pre existing dessication crack?

Ben


Posts: 2270

Reply: 278



PostPosted: February 22, 2010 7:29 PM 

Serpens; My assumption is that the pellets are formed of dust eroded from Meridiani beds which has been lofted by cyclic storms.

It has also been my impression that the berries are more concentrated in the alternating harder layers.


I would go so far as to say that upon further study they may be found to be limited to the approximate vicinity of the plains .

Barsoomer


Posts: 344

Reply: 279



PostPosted: February 22, 2010 8:16 PM 

> Could it be that the complex irregular grain is where rock fractured violently on impact ...?

Serpens, I had in mind surfaces more like this

and also the surfaces with polygonal cracks, and other less grainy ones, rather than violently fractured surfaces.

LWS


Posts: 3062

Reply: 280



PostPosted: February 22, 2010 9:03 PM 

Barsoomer

Thanks for your observation on the predominant types of rocks the crust seems to be formed on.

Another thing that seems very atypical about this site is the size and look of the berries. They're very small, many are distorted and there seems to be large numbers of "pebbs".

Here's a colour composite of one of today's images that focused on berries in the soil

Winston

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