On the Road Again - volume 5 - Page 19

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Barsoomer


Posts: 344

Reply: 361



PostPosted: February 27, 2010 2:46 AM 

link

The above later paper, which includes Jim Bell and Steve Squyres as coauthors, gives a somewhat higher estimate for erosion rates on Mars of 1-10nm/year.

So if Concepcion Crater is 1000 years old, the rocks should have eroded by only 1 to 10 microns, i.e., we should not see any erosion. Even if the crater is 100,000 years old, we should only see between 100 microns and 1 mm of erosion. This suggests that some other factor at this location is resulting in additional erosion. What could it be? I guess since the rover science team includes Bell and Squyres, we might see this issue addressed at some point.

LWS


Posts: 3062

Reply: 362



PostPosted: February 27, 2010 7:17 AM 

Barsoomer; Excellent point! At the other site we could always be told that we were looking at billions of years of erosion. Here that explanation can't be given. I'd be also very curious as to what they have to say.

Winston

Ben


Posts: 2270

Reply: 363



PostPosted: February 27, 2010 1:48 PM 

Winston; In Horts #356 image there is a rock on the far left,middle that shows the planar, pre-impact surface with fracture fill on the left side a short distance below that surface.

I interpret this to illustrate the process that formed the fractures and fill prior to impact.

The smaller chunks with fill that don't have any of the original surface exposed ,are from the subsurface where some horizontal cracks would be expected.

If this is a post-impact coating what would control the erratic loci of deposition? Confused

Barsoomer


Posts: 344

Reply: 364



PostPosted: February 27, 2010 7:51 PM 

A crop from Horton's image in #346. A nice berry on stem apparently from a similarly sized tiny rock. Note what looks like a remnant of the crust material hanging from it. Are the crusts and the berries on stems related in some way?

LWS


Posts: 3062

Reply: 365



PostPosted: February 27, 2010 9:45 PM 

Ben; Re your #363. I think you are referring to the largest rock on the left of my composite below

I totally agree with you that this looks like a rock that came directly from the surface. The rock had a fissure and some of the fracture fill can be seen adhering to the left side of it. The angle of the picture makes it difficult to be certain if the "fill" resembles the crust that appears to be so typical of the concepcion rocks or not. It looks more like a normal meridiani fill like the one seen below.

Hopefully they will image this rock more extensively later.

You said "If this is a post-impact coating what would control the erratic loci of deposition?"

I suspect we may have to wait a bit longer for a fuller picture to emerge as to any loci of deposition. For now the deposits appear to be quite random, primarily on vertical cracks but with a few on planar cracks and with no obvious deposits so far on the planar surfaces of rocks which apparently came from the original pre-impact surface.

It is almost certainly not impact melt from the images i've seen so far of impact melt.

Barsoomer;

I think that they well might be. Some images suggest that the crust material, with well demarcated areas on which berries are present on the surface and smooth surrounding areas resemble a number of lichens. In addition, at least one of hort's 3D images suggested that the crenellated edges of one of the cusps of a piece of crust might be a fairly complex structure.

Winston

LWS


Posts: 3062

Reply: 366



PostPosted: February 27, 2010 10:53 PM 

Ben; I hadn't seen any comments about this rock below which was first posted over a week below

Below is another one like it. Any ideas on what it might be? There's an earlier image which had impressions of blackened "berry on stalk-like" outgrowths projecting in all directions. I'd never seen similar looking rocks earlier.

.

Winston


Barsoomer


Posts: 344

Reply: 367



PostPosted: February 28, 2010 12:30 AM 

link

The above links to one of the 3D images linked to in Horton's #321.

This one is very striking, especially if the central area is viewed in stereo in the large size.

It seems to be showing a fossilized record of a crust in the act of engulfing and consuming a rock. At the margin of the crust one can clearly berries sprouting from the crust, not the host rock. The berries are pointing in all directions here, rather bending towards a prevailing wind, so it is difficult to see how they could be "wind tails."

I think we are seeing something strange and wonderful here.

Serpens


Posts: xxx

Reply: 368



PostPosted: February 28, 2010 12:43 AM 

Barsoomer. That is the rate of erosion at the Pathfinder site estimated for the Pathfinder site. At the Opportunity site I believe it was calculated that no more than 2 meters of evaporate material has been eroded since it was laid down. But wouldn’t the wind energy sufficient to move the Meridiani armoured dunes would also be pretty abrasive to the evaporates, lag deposit notwithstanding? So either the erosional energy at Meridiani was greater than at Pathfinder, or the evaporates eroded faster (a distinct probability) or the dunes have been frozen a lot longer than some think. (There are probably a lot of other scenarios). But everything I see here at Concepcion leads me to believe that the crater is a heck of a lot older than some intimate.
Winston, the heat energy from an impact the size of Concepcion is really quite minor and would dissipate very quickly. What they are talking about is a massive impact, and probably the bottom of the scale would be something the size of the Gusev crater impact which would have been millions of megatons. It may have taken that crater many years to drop to ambient, but after a bang like that I don’t think that there would have been any life left in that crater to bask in the warmth.
Finding fracture fill exposed by impact is logical and consistent given that we have seen eroded remnants at a lot of places in Meridiani. If this was some kind of current biological artefact as you espouse then why have we not seen it all over the surface of Meridiani?
Confused

LWS


Posts: 3062

Reply: 369



PostPosted: February 28, 2010 1:07 AM 

Hi Barsoomer;

This one below is a collage I did showing a rock from yesterday's images with lots of berry stems and no possibility of wind tails since some of the stems are in a hollow. It looks like a berry factory.

In the collage I'm contrasting the newer image with an older one of chocolate hills showing berries and what was called wind tails (many of them) curving in and out down the rock. I suspect if we get more rocks like this with stems the case of wind tails vs. stems will be closed.

Winston

Barsoomer


Posts: 344

Reply: 370



PostPosted: February 28, 2010 2:20 AM 

Winston thanks, your image demonstrates that the stems do not have a preferred direction, as one would expect (towards the prevailing wind) if they were wind tails.

How about adopting as a working hypothesis that we are seeing some kind of life form? If so, what can we discern about its life cycle, based on what we are seeing? Your idea about lichen is an interesting one. Indeed, in the pre-Viking days, lichen was something that scientists speculated might exist on Mars. However, I wonder if under Martian conditions, the symbionts might be something different. Perhaps the algae or cyanbacteria might be replaced by rock-eating bacteria, for example.

LWS


Posts: 3062

Reply: 371



PostPosted: February 28, 2010 9:42 AM 

Hi Barsoomer;

That has been one of my working hypotheses for years now but one which I had almost jettisoned because of the sheer authoritative weight of the JPL model (as serpens would call it). The Concepcion images gave that working hypothesis new life.

I now think that there might be a range of biota living not too far from the surface underground in the cracks and crevices of rock and with access to relatively frequent upswellings of water. I think the stems, with their winding long pathways and seeming interconnections are possible conduits for exchange of materials and are an essential part of the organisms. I think the berries are also essential organs that are resistant to surface conditions and provide some essential function. I think periodic impacts and soil movements provide some avenues for dispersion of the berries. I think the stems are too fragile to survive above ground and so they disappear relatively soon after exposure and when in the top layer of the soil.

I think a tentative life cycle may be something like; lichen like organism and separate symbionts exist underground in crevices in the rocks; impact occurs and some rocks with symbionts scattered and dispersed on surface; rocks weather to release berries on the soil; dust covers berries; surface becomes indurated; cracks form; organisms become active in water cycle in cracks; on to next disturbance of rocks; cycle complete.

THere are still lots of gaps in this tentative cycle but if the Concepcion images continue to throw up new objects in the way it has started some more information might evolve to fill some of those gaps.

Hope they don't move off without thoroughly examining concepcion. eg. taking some MIs of those areas with clear stems; mapping the existence of the crust on various types of rocks; etc. However, the experience over the last 6 years has been that the rover team is only interested in rocks and water. Nothing else can exist on Mars.

A pity.

Winston

James


Posts: 3

Reply: 372



PostPosted: February 28, 2010 11:11 AM 

re levitating fracture fill...
Water-ice packed into fill prior to small impact which exhumes this fill/ice matrix, causing quick sublimnation of ice, leaving the present delicately eroded features.

Barsoomer


Posts: 344

Reply: 373



PostPosted: February 28, 2010 1:20 PM 

That's a good thought James. That would also explain the crust overhanging the edge without invoking rock erosion.

Ben


Posts: 2270

Reply: 374



PostPosted: February 28, 2010 1:51 PM 

Winston; Response to your question in #366,
I have no explanation for your first image other than the pebbles in the depression on top of the rock must represent max wind (whatever that is) which couldn't move them.

The area noted in the second image appears to be shaded with a coating of dark dust.

Where the fill drapes over the rock, I interpret that to represent the pathway of (fill depositing) fluid moving horizontally in a crack.

LWS


Posts: 3062

Reply: 375



PostPosted: February 28, 2010 2:25 PM 

Here's a diagram attempting to show some gross comparisons between the morphology of some lichens and the concepcion crusts and berries. Still a work in progress

Ben / Serpens / James; Thanks for your interpretations of the various images.

Winston

Kye Goodwin


Posts: 1166

Reply: 376



PostPosted: February 28, 2010 3:49 PM 

I guess Oppy will be moving on soon. I'm going to try to summarize what I think we saw at Concepcion:

1. It isn't clear whether or not this is a particularly recent crater. There is proportionally much more small breccia in evidence here than at any other crater but that doesn't tell me much. Berry stems and unevenly eroding layers in breccia blocks suggest that at least a few cm of erosion of the surfaces of the rock rubble has taken place since the impact.

2. There are a lot of ejecta block surfaces coated with sheets of material consistent with pre-impact fracture fills. While commoner here by far than elsewhere they still cover only a small percentage of the rubble surfaces. (Fills on rubble are not entirely novel at Meridiani. There appear to be a few examples of fills and rinds on the breccia of Beagle Crater.) These fills at Concepcion are the first that we have seen face-on rather than cross-sectioned from above.

3. The one really novel feature here is the presence of "layers" of coarser material appearing sorted "in" the fills. I'm using quotation marks as a substitute for sufficiently vague language. I think that we have seen only two good examples of this but one was confirmed with the MI:

Because the coarser material of spherules and fragments appears to be embedded in and cemented by the fill "fines", we can say that the fines were introduced along with or after the "sheets" of coarser material. How the sorted thin layers of coarse material formed vertically in the fracture is the conundrum. I don't think that we have enough good examples to make much of this, but vague as I am, this sorting and layering seems more consistent with an energetic arrival of all the fill materials together than it does with precipitation of minerals from water or slow cementing of soil.

serpens


Posts: 169

Reply: 377



PostPosted: February 28, 2010 5:21 PM 

Kye Goodwin. Good summation although I don’t think your energetic injection (surge) idea holds. While I appreciate that the ground water recharge concept is you bête noire it explains the layered fracture fill. Desiccation cracking, some debris falls in, recharge cements to cause a fracture fill, further desiccation and crack widens, and the process repeats a few times forming laminated layers. Given the thinness of the laminations I feel that the excavated fill comes from a wicking area, not the actual water table.

The depth of the thin layering with layers of differing cementation strength, some cross layering and occasional festooning is consistent with cyclical deposition. I don’t think that there is any evidence of surge. The explanaion that such layering could possible appear at the distal area of a surge has really lost credibility given the distance that Opportunity has travelled with the same cyclical evaporate layering evident.

Ben


Posts: 2270

Reply: 378



PostPosted: February 28, 2010 6:05 PM 

Serpens; I am with you except for the wicking process. Wouldn't the presence of (fallen) berries in the fill indicate a fracture a bit wide for this?

Bill Harris


Posts: 72

Reply: 379



PostPosted: February 28, 2010 9:47 PM 

Ben:
> I am with you except for the wicking process. Wouldn't the presence of (fallen) berries in the fill indicate a fracture a bit wide for this?

I don't look at it as so much wicking as crystallization from a saturated/supersaturated solution of Mg+Fe+SO4+??. Remember the Kieserite is soluble to begin with, and the phreatic surface is at Martian atmospheric pressure, so the water "boils off", concentrating the solution even more. Once the salts start crystallizing in even a wide fracture, the effective porosity closes up and the water table goes vadose. Add accumulated sands and berries in the fracture and the whole thing wicks.

I'm trying to pin down crustal heat flow on Mars, the guesstimates are all over the board. The magic depth is where the crustal temperature approaches 0*C...

--Bill

Barsoomer


Posts: 344

Reply: 380



PostPosted: February 28, 2010 9:49 PM 

Kye, why do you and others continue to view the stems as signs of erosion, given the following contrary evidence that supports a pre-impact origin:

1. Berries on stems projecting forward from the margin of the crust (post #367), seemingly part of the crust.

2. No preferred direction for the stems (post #369).

3. A solitary stem emanating from a tiny rock (post #364)

4. The slow erosion rate at Meridiani as estimated in a paper by the MER science team (post #361). The crater would have to be at least 2 million years old to erode 2cm, which is inconsistent with JPL estimates.

The idea of James (post #372) that parts of the ejecta were encased in ice that sublimed explains a lot. It explains the seeming paradox of an obviously young crater having apparent extensive erosion. It also explains how delicate features such as the berries and stems could have a pre-impact origin and yet survive the shock of the impact.

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