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Posted by: Kye Goodwin Jul 10 2007, 04:37 PM

I have been reading the response to the reponse to impact-surge linked by Dr Burt in post 170. The MER team objects to the impact-spherule explanation because " The spherules are dispersed nearly uniformly across all strata." I agree that is a valid criticism. It is very much like Dr. Burt's criticism of the MER team's hypothesis, that spherule distributions are not consistent with any conceivable ground-water movement regime that should have controled the development of concretions. I agree strongly with this point of Dr. Burt's as well. Neither theory does a good job of explaining the distribution of the spherules. Also, neither theory does a good job of explaining why the spherules do not apparently disturb the bedding.

There may be a solution in a possibilty that I now raise with some trepidation. I think that there is a chance that the spherules are superficial, and not an integral part of the Meridiani strata at all. This probably sounds crazy to many readers, but before rejecting it outright remember that science is at kind of an impasse on this and could use a new idea. If the spherules are superficial this would explain a number of puzzling observations.

The layering at Homeplate and Meridiani is most simply explained by impact-surge. It is elegantly and inescapably explained by impact-surge. The impact-surge authors have also tried to explain the Meridiani spherules as part an impact event. If doubts are raised that the spherules are integral to the deposit, this would not in any way be inconsistent with the impact-surge origin of the layered structure. On the contrary, an objection to impact surge would be removed.

I intend to start another thread under Opportunity to discuss this question. The first posting should be mine and should be an organized outline of how it might be possible that the spherules have been mis-interpreted as part of the Meridiani layered deposit. I am working on it. If anyone wants to start in on me with the obvious objections, do it here for now. Maybe Dr. Burt would like to respond. No matter what the details of spherule formation in an impact or spherule deposition in the impact sediments, the very uniform distributions that we see are troublingly unlikely. Random distributions are possible from explosive dispersal but less likely than some kind of clustering because of the rapidly changing conditions in the surge cloud. The more-uniform-than-random distributions of spherules on rock characterised by MER-team analysis cannot be explained by impact surge.

Posted by: djellison Jul 10 2007, 04:53 PM

I've seen you mention your theory that the spherules are essentially a surface feature. The problem I have with that is why, then, are there non in the outcrops up around Erebus? Why are they different from the top ( Eagle ) to the bottom ( low in Endurance ). How do you explain the fact that some were found within the rock itself visible only after a rat grinding? Or - if you can expain that - then what evidence is there that they exist to a depth exposed by the RAT, but no further? What mechanism for their formation can you come up given their composition? Seems to bring up more questions than observations it explains.

Doug

Posted by: Kye Goodwin Jul 10 2007, 07:12 PM

Doug Ellison, Thanks for asking. It will be a long haul I expect to get anyone to take this idea seriously. I have been through this debate before on the Mark Carey site and I think I did eventually convince a few people that there is some merit in the idea that the spherules are superficial.

Here are two MI's that show the surface of an outcrop on the rim of Vostok Crater before and after brushing:

http://marsrovers.jpl.nasa.gov/gallery/all/1/m/400/1M163693341EFF5000P2956M2M1.JPG

http://marsrovers.jpl.nasa.gov/gallery/all/1/m/401/1M163783537EFF5000P2956M2M1.JPG

I interpret these two images this way: Before brushing the surface of both the spherules and the surrounding outcrop rock is coated with a bright mineral that is more consolidated than a coating of air-fall dust. The coating does not have the texture of dust and covers the vertical sides of the spherules and rock fractures has well as the horizontal surfaces. I think that this is an accreted mineral rock coating. The disparate minerals covered, the hematite of the berries and the sulphates of the rock, make it very unlikely that the bright layer could be an alteration rind, because the two different substrate minerals could not plausibly be altered to the same bright mineral. Further, because the coating covers a rough contempory surface made up of both exposed spherules and rock, it is almost certainly fairly recent in origin. Accreted rock coatings are not a new discovery on Mars. Several examples were evident at the Pathfinder site. Here is a Kraft and Greely paper that discusses the Pathfinder coatings with particular reference to the balance between aeolian abrasion and rock coating formation, which would be opposed processes. They conclude that rock coating formation is probably proceeding more quickly at the Pathfinder site than is aeolian abrasion.

http://www.lpi.usra.edu/meetings/LPSC99/pdf/1686.pdf

Since Oppy landed I have seen many references to erosion at Meridiani. I think that accretion is also taking place there. The results of this brushing experiment at Vostok are not unusual at Meridiani but typical. Bright rock coatings are forming over the surface of the bright rock and spherules.

A second example of accretion at Meridiani is the formation of the rinds investigated by the MER team. I think that these too are recent additions to the outcrops but I will get to them in another post. The impact-surge authors have suggested that salt efflourescence could be an active process at Meridiani. The erosion of the Meridiani outcrops is not by any means the rule in the present era. Maybe some readers can see were I am going with this. I hope to post more later today.

Posted by: MarsIsImportant Jul 10 2007, 07:30 PM

Kye, How would this be a test for either hypothesis? I would think accretion coatings would be allowed for either, so how would this observation favor one over the other?

Posted by: djellison Jul 10 2007, 08:11 PM

Apart from 'it looks like' - on what basis do you draw that conclusion? Martian dust is perfectly happy to cling to vertical surfaces (see the Sundail Gnomon for example) - Have you compared pre and post rat spectra?

And to be honest, this doesn't touch any of the issues I raised about your theory.

Doug

Posted by: Kye Goodwin Jul 10 2007, 11:21 PM

MarsIsImportant, If the spherules are superficial, that is, not really a part of the Meridiani layered deposits then neither theory needs to explain their distributions or their relationships with the bedding.

Doug, You never give an inch, do you, even for the sake of friendly debate? I do not need to prove that accretion is taking place at Meridiani, but only to raise doubts that it might be. I think it is reasonable to think that rock coatings might have formed at Meridiani based, yes, in part on the appearance of pre and post brushed surfaces. The little bits of bright material left behind at the base of those spherules encourage me because if they were unconsolidated dust they might have been removed by violent air currents close to the spinning brush. Here is the abstract for a talk in which several MER scientists discussed fracture fills and rock coatings at Meridiani, not as processes from an ancient warm-wet Mars but as something that could have happened under conditions more like those found today.

http://www.aas.org/publications/baas/v37n3/dps2005/424.htm

Did you get a chance to read that Kraft and Greely paper? They seem quite willing to accept that rock coatings formed at the Pathfinder site. The rinds like Lemon Rind were thought by the MER team to be added to the top of the Meridiani strata after all other deposition was complete. They haven't said that the rinds are recent, but I maintain that they might be. The rinds sometimes wrap the corners of eroded blocks and occur in the ejecta of not-so-ancient Beagle Crater.

My point is that erosion may not be the only process recently affecting the "rock" at Meridiani, which we should remember is barely rock at all. Spherules are embedded in "rock" allright but that is not proof that they formed or were deposited deep within the layered strata. This gets me to the MI evidence of the relationship between the spherules and the layers but I'll leave that for the next post.

Posted by: Kye Goodwin Jul 11 2007, 12:40 AM

Centsworth_II, OK. I will start a topic under Mars because this question is not just about Meridiani. If anyone is interested, please post to "Could the Meridiani Spherules be Superficial?" I hope to hear from Doug. If Dr Burt wants to comment I will look for that here. I may post again to this thread on this topic because the spherules are a serious problem for both theories, and will come up again and again. The basic problem is that the spherule's appear to have no relationship to the surrounding rock. I think we should consider if this is simply so.

Posted by: Pavel Jul 11 2007, 01:00 AM

I'm not a geologist, but I majored in solid state physics. It seems very unlikely to me that round spherules would form in anisotropic conditions between the layers. Even in isotropic conditions, solid concretions would take the shape of crystals, unless there is a force canceling out inherent anisotropy of the material. Surface tension is one possibility, but it would mean that the spherules formed from molten liquid, probably in a hot gas and rained down on top of the forming sediment. Another possibility is the mechanical force grinding the solid spherules, but I fail to see how it would make the spherules round between the layers, again due to the anisotropic geometry. In fact, mechanic forces fail to produce round pebbles on Earth despite the conditions when the pebbles can and do rotate. There is also a faint possibility that the layers "stratified" after the spherules formed, but the layers are too similar to each other, and that would be against the second law of thermodynamics.

The end result is, I have hard time believing that the spherules formed in place. It's easier for me to believe that they came from a nearby volcano or even from space.

Posted by: Kye Goodwin Jul 11 2007, 01:01 AM

I have started writing on this topic on the thread that welcomes Dr Burt. For continuity I will copy in the three posts that I made to that thread. I hope that is OK Doug. If you have another way to link the threads erase this and do it do it your way. I hope to hear from you.

I have been reading the response to the reponse to impact-surge linked by Dr Burt in post 170. The MER team objects to the impact-spherule explanation because " The spherules are dispersed nearly uniformly across all strata." I agree that is a valid criticism. It is very much like Dr. Burt's criticism of the MER team's hypothesis, that spherule distributions are not consistent with any conceivable ground-water movement regime that should have controled the development of concretions. I agree strongly with this point of Dr. Burt's as well. Neither theory does a good job of explaining the distribution of the spherules. Also, neither theory does a good job of explaining why the spherules do not apparently disturb the bedding.

There may be a solution in a possibilty that I now raise with some trepidation. I think that there is a chance that the spherules are superficial, and not an integral part of the Meridiani strata at all. This probably sounds crazy to many readers, but before rejecting it outright remember that science is at kind of an impasse on this and could use a new idea. If the spherules are superficial this would explain a number of puzzling observations.

The layering at Homeplate and Meridiani is most simply explained by impact-surge. It is elegantly and inescapably explained by impact-surge. The impact-surge authors have also tried to explain the Meridiani spherules as part an impact event. If doubts are raised that the spherules are integral to the deposit, this would not in any way be inconsistent with the impact-surge origin of the layered structure. On the contrary, an objection to impact surge would be removed.

I intend to start another thread under Opportunity to discuss this question. The first posting should be mine and should be an organized outline of how it might be possible that the spherules have been mis-interpreted as part of the Meridiani layered deposit. I am working on it. If anyone wants to start in on me with the obvious objections, do it here for now. Maybe Dr. Burt would like to respond. No matter what the details of spherule formation in an impact or spherule deposition in the impact sediments, the very uniform distributions that we see are troublingly unlikely. Random distributions are possible from explosive dispersal but less likely than some kind of clustering because of the rapidly changing conditions in the surge cloud. The more-uniform-than-random distributions of spherules on rock characterised by MER-team analysis cannot be explained by impact surge.

Posted by: Kye Goodwin Jul 11 2007, 05:09 AM

I have a feeling that I have already lost eveybody, but I think that I should try to finish an outline of this idea anyway. The gist of it is that I think the spherules have simply formed where we see them. I could call them sub-aerial concretions but nodules would do. I am not sure about the sub-aerial part either as a cover of dust, soil, snow or even sulphates might be involved. I think that the spherules on soil have formed on soil and that the spherules on rock have formed on rock. In that way at least this is a very simple idea.

The absence of distorted layering adjacent to attached spherules is a troubling observation for both theories. The MER team has had to complicate their concretion hypothesis by suggesting that the concretions replace the surrounding rock. This asks a lot more of the concretion growth process than distorting the surrounding material or including it in the concretion. For the impact spherule theory the failure of the spherules to locally distort layers is a serious problem. No matter what mechanism is involved in creating the layers or depositing the spherules I think that we should see some evidence of interaction. My explanation is that the spherules have never been within the layered material.
There is no clear MI evidence that the spherules have distorted layers. This is negative evidence. It is convincing because with all those berries putatively in layers some distortion should be visible. Even at pancam scale distortion of the bedding should be visible and it is not visible even where many berrries can be seen together on layered surfaces. The complementary observation that spherules truncate rather than distort layers cannot be made. There are no MIs of layers clearly ending against spherules and one cannot see this sort of detail clearly in pancam images. There is no direct visual evidence that spherules have formed or been deposited within layered material. Everything that we see can also be interpreted as spherules that have formed on the surface of layered rock or been embedded by accretion.

Attached spherules in MIs usually show no evidence that they have protected the rock from scour erosion even when they are standing almost their full diameter above the rock, a condition that occurs often. Rock wind-tails with spherules are very rare and are ambiguous because of their multiple orientations, while spherules are often surrounded by indefinite extensions of the rock resembling tufa or efflorescence that show no streamlining or coordination of directions. My explanation is that much of the surface at Meridiani is accreting rather than eroding and that many exposed spherules may have never been deeply embedded.

The occurrence of similar spherules uniformly distributed over the surfaces of a surprising depth and apparent diversity of strata at Endurance Crater is a key observation for testing both theories. Both fail in my opinion for the reasons that their respective opponents have published. It is implausible that concretions would be distributed in a way that does not reveal clustering associated by groundwater movements and it is also implausible that impact spherules would be so uniformly distributed. A random distribution could result from surge but I think that the more-uniform-than-random distribution that the MER team characterised is real. I think that this is a powerful reason why the MER team has stuck with the concretion hypothesis. My explanation is that the spherules have formed in a surface environment that postdates the crater and thus is common to all exposed strata. They are evenly distributed because their growth has been limited by environmental factors. This is also how the MER team explains the uniform distribution but they have placed concretion growth long ago under a different climate and deep within the layered rock.

Spherules on soil display remarkably uniform distributions at meter scale over thousands of square meters. This is difficult to explain by gravity or wind emplacement. My explanation is that the spherules on soil have not been mechanically emplaced but rather have formed in-place limited by environmental factors.

Spherules are very prominent in the Meridiani landscape, almost covering the surface of the soil and in most places standing out above the surface of the rock. Most show no evidence of erosion. If they are very old we have been lucky that they are now so intact and obvious. The explanations of why they are so prominent after billions of years are reasonable but it could have been different in many possible ways so that the spherules might not have ended up so well displayed in our time. I think their prominence is better explained by their relatively recent origin.

Posted by: djellison Jul 11 2007, 07:36 AM

It's not about 'giving an inch', and compared to other places, hell, this is still friendly if you ask me

You've proposed a theory on the origin of the spherules. I've raised some issues that I think question that theory- and yet you've twice posted about something else (coatings) rather than tackle the issues raised. Indeed - you're ignoring them. The Spherules in the rock are NOT the same for the full height of the endurance outcrops. They're different from the top to the bottom - and they're totally absent by the time you get to Erebus. You can not possibly explain that if you maintain a surface origin for them.

There IS evidence that they formed within the layers - bellybands have been observerd where they have formed and grown a little between layers - the berries will not have distored layers, the layers distorted the formation of the berries it would seem. Why does this make concretions more 'difficult' to believe. What terrestrial analogues for spherules-in-rock can you cite to say this is not the case? Some have appeared only AFTER a rat hole has been formed and thus catagorically not on a modern surface - unless you are suggesting that many MM's of sulphate / jarosite rich rock are being desposited today.)

If you've ever tried to cut a piece of hematite with a dremel or a drill, you'll know why they exhibit little erosion. A diamond tipped cutting machine takes a couple of hours to get through one, whereas the rock takes a few minutes.

Why is the transport of the berries so hard to imagine via wind...this is a wind that almost totally eroded a wheel track in less than a year. (infact, in the most recent case almost within a week) Imagine what it can do with a billion years.

If you're challenging other theories because you think they have issues, then you have to expect issues to be similarly raised about your own theory. It's not giving an inch - it's exercising the same critical thinking you say you're using with other theories. Of all the theories, it's the one that I have the hardest time buying.

And of course, the biggest issue of all...how do you creative hematite rich spherules on the surface of Mars?

These issues are not about giving an inch. If someone said "they were put there by the berry-ferry" but then couldn't explain how, or why, or answer to some of the contrary evidence then essentially all you've got is a belief system. That isn't science.

Doug

(I've merged the posts from the other thread into this one - they're sit slightly out of order, but it makes sense)

Posted by: MarsIsImportant Jul 11 2007, 02:12 PM

I agree with Doug.

The spherules are basically made of hematite. It's possible the accretion coating you cite (if it is that) is something other than dust (I doubt it), but it cannot be hematite given the environment of Mars and Meridiani. Another problem is somehow finding a mechanism that would change the coating into spherules. You would also need to adequately explain the age problem with various known geologic features. It all seems complicated, as well as some steps seeming to be impossible. In my mind, you would need a volcanic surge cloud that remained just a few centimeters in height over many kilometers--the span of Meridiani. And it would have to do this many times to embed the spherules in deeper layers. That's just not plausible.

Perhaps I just don't exactly understand what mechanisms for the appearance of the hematite spherules you are actually proposing. It sounds like accretion of hematite. How exactly would that happen without a major surge cloud of some kind?

Posted by: Bill Harris Jul 11 2007, 02:46 PM

This is not a court of law and you don't need to introduce reasonable doubt. This is science and you need to prove the hypothesis. You've expounded on a belief, which is incorrect. You should not give up your day job in landscaping...

--Bill

Posted by: Kye Goodwin Jul 11 2007, 05:54 PM

Bill Harris, I can't prove anything by posting, which is a discussion about science, not science itself. The goal is to entertain each other, bring observations and relevant publications and maybe get a little closer to the truth eventually together. It might be a long time before any overall theory explaining the rover results is proven by anyone. Meanwhile we should be thinking rationally but with some imagination. Also, raising doubts is a legitimate way to think scientifically. Nothing blocks progress like an unexamined assumption that turns out to be wrong.

Doug, thanks for getting back to me. I don't know why I made that comment about giving an inch. I guess I was disappointed that I was really going to have to work hard to establish to your satisfaction that there are rock coatings at Meridiani. My introduction of the alleged rock-coatings was not a direct response to your objections but I was going there with it. Let's get to some of your specific points from the third post of this thread.

I have never been sure from the images just how uniformly the spherules are distributed through the Endurance strata or if there are any discernable trends in their size and shape from top to bottom. In their response to impact surge the MER team writes, "The spherules are dispersed nearly uniformly across all strata." I haven't seen a paper describing differences in size or shape with position in the crater. Any change in the spherules with strata might support both the impact spherule theory and the subsurface concretion theory because they both have a problem with too much uniformity. If the spherules are superficial I would expect some variations because of different microclimates and possibly different disturbance histories. The spherule sizes definitely vary systematically at kilometer scale as you say, but I don't think that fact helps us much, as it can be interpreted to support many theories.
The belly-bands on loose spherules are created by the level of the soil surface during growth in my theory. Many of the spherules are near perfectly spherical, including many attached to rock. It has always been hard to understand how their growth within coarse-textured rock has affected them so little. The subsurface concretion theory would be much more plausible if the spherules incorporated the grain textures of the rock or grew irregularly between the grains. Dr. Burt sees the lack of shape variation as a fatal problem for the concretion theory. I explain the lack of any discernable effects of the rock on the spherules as evidence that they did not grow within the rock but at the surface.
Yes, I am suggesting that several mm of sulphate accretion has happened in some places. Wherever the layering can't be seen an unknown amount of accretion may have taken place. The limit on this is the layering. If the layering has not been obscured then there is a shallow limit to how much accretion has happened, but this is complicated because in some places the layers have been deeply eroded and there it would take more accretion to hide them.
I was not arguing specifically that the hematite spherules should have eroded away in billions of years so the issue isn't how hard they are. I am trying to make a general point that we got very lucky, maybe too lucky, getting to see all this interesting stuff at both Gusev and Meridiani if it was all created billions of years ago. In a lot of places it would be covered over or eroded away. I suspect that we are getting such a good look at all these water-altered minerals and structures because many of them are relatively recent in origin.
Transport of the berries by wind is hard for me to imagine because their present distributions on soil are so uniform. Wind would push them into granule ripples almost immediately if it could move them at all.
How do I explain the formation of hematite on the surface of Mars? I don't. It doesn't happen like that on Earth, so it is a mystery with no known analog. Because I have been fairly confident for more than two years that impact-surge would explain the Meridiani deposits I have a different view of Mars than most. I don't explain any of the water chemistry and chemical structures (fills, rinds, coatings, spherules, popcorn spherules, etc) as products of an ancient warm climate. I think that these are processes that can and do happen under current or recent climate conditions. I take all the evidence of water chemistry as support for the plausibility of surface spherule growth.

MarsIsImportant, I was not suggesting a direct link between the rock coatings and the spherules. I was using the presence of a mineral, the rock coating, which I think has formed recently to support the recent formation of the spherules. I was also suggesting one way in which spherules might become enbedded in rock by being covered in coatings.

Posted by: climber Jul 11 2007, 06:12 PM

...and back on VC apron.
Question: The decision to land at Merdianii has been taken relying on data from orbit. Do we have finest (spacial) mesurements now where we can see Berries concentrations and absences?

Posted by: djellison Jul 11 2007, 06:33 PM

This page - http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040818a.html - highlights many of the problems with a surface genesis for Spherules and active surface creation. It's a different composition at the top than the bottom - as well as berries being different ( and indeed absent ). Why is there material forming on rocks hiding berries, but not on the soil. Why is there a composition change in the surface that ties in to the morphological evidence as seen at Endurance if the surface is modern?

All credit for thinking outside the box - and without serious challenges, no scientific hypothesis can be said to be a robust or reliable one!

Doug

Posted by: helvick Jul 11 2007, 07:06 PM

Kye,

I'm all for thinking outside of the box too but the idea must be able to explain all of the observations. One nit pick - I think the word you should be using is "surficial" rather than "superficial".

In any case.

1. To focus in on one area where I think HDP Burt has fewer dead grandmas than the MER team. What process are you going to use to create "high temperature shiny blue hematite" ? As far as I can tell the MER team's explanation relies on a very specifically balanced saturated brine as a plausible explanation but the high temperature surge "hailstone" idea seems (on balance) less dependant on a carefully balanced system. Both hypotheses are hampered by a complete failure to indicate an equivalent earth analog but then that would be asking for quite a lot.
2. Pavels comments on the mechanics of the formation process are very compelling and really problematic for your surficial formation hypothesis. Do you have any example(s) of a (non biological) process anywhere that produces fairly uniform spheres of any predominantly solid material?
3. At the most basic level we see lots of berries free on the surface, they are certainly embedded to a depth of a couple of mm in most of the RAT'ed rocks and they are present at the surface of all exposed rock formations. The simplest explanation is that they are present throughout the rock and those that we see on the surface have eroded out of the rocks. Your explanation may be possible but it seems overly complicated to me.
4. I don't see how your hypothesis resolves any of the difficulties with the two other hypotheses? Maybe I haven't read it all carefully enough though.

Actually to be honest I'd love to see one of the proper geologist types who are reading here lay down some basic pros and cons for the various ideas. Most of this stuff is way outside any area that I have any expertise in - for example I have no idea whether the claim that "shiny blue hematite" requires high temperatures to form is true or not, or how true it is as I suspect that the issue isn't totally clear cut.

All that said I've found all of these discussions extremely worth while and I hope they can continue.

Posted by: Kye Goodwin Jul 11 2007, 10:57 PM

helvick re your post 17, Thanks. On superficial vs surficial, yes my language tends to be a mish-mash of English and technical terms when I think I understand them. I can go with surficial if you like, but its too late to change the title of the thread.

1. Here is a Tim Glotch paper that concludes on the basis of crystal structure that the spherules have probably formed under low-temperature conditions:

http://www.gps.caltech.edu/~tglotch/glotch_fresnel.pdf

2. Pavel's mention of surface tension as a possible cause of sphericity might somehow relate to surface spherule formation. Thin films of moisture are often invoked to explain how water could act under Mars surface conditions. I have to admit that I haven't been able to come up with a compelling reason why my surface nodules should be round and it bothers me that they do not usually show top to bottom asymmetry. One GUESS is that the sphericity and the size limit are related to the microclimate that the berry creates during a daily period of fleeting moisture.

3. and 4. Yes, at a glance, the simplest explanation is that the spherules occur throughout the rock, but on closer inspection problems remain. The surface nodule theory solves two of the thorniest problems faced by both the impact spherule idea and the sub-surface concretion idea. It explains why the spherules do not disturb the bedding layers, and it explains why the spherules show no clustering, not along bedding planes or apparent contacts in the rock, or in any way that would suggest that they were controlled by groundwater movement.

Posted by: MarsIsImportant Jul 12 2007, 12:54 AM

Kye, that is an excellent paper!

It pretty much rules out high temperature formation of the Martian hematite spherules. That means no volcanic lapilli, and impact surge is also ruled out. These berries were created at low temperatures. That also means that the MER team is 'in the ball park' so to speak. This is strong evidence to support the MER team's hypothesis.

I am curious as to how you could form an alternative low temperature hypothesis that creates these spherules on the surface. Since you have some good sources, I am willing to have an opened mind. But on the surface (a pun), this looks like a crazy idea for an alternative. I'm listening.

Posted by: djellison Jul 12 2007, 07:11 AM

The varying morphology and density as seen at Endurance, Eagle and Erebus would be indicative of such movement would it not?

Also - invoking any water at the surface to create the spherules would preclude the existance of Olivine
http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040204a/mb_soil_opportunity_bw-B011R1.jpg

i.e. http://www.astrobio.net/news/article653.html
"Olivine is significant because it decomposes rapidly in the presence of water. Finding olivine on the surface is therefore a good indicator of a dry Martian surface."

Now - it does say one of the things it can be decomposed into is hematite - but - how does the decomposition of soil turn into a hematite rich ball and/or how can there still be olivine when it's widely assumed Mars has been just about the same for a billion years or more.

Doug

Posted by: dvandorn Jul 13 2007, 04:29 AM

OK -- here are two points that might possibly lead to further discussion. Here's hoping.

First point: If this hematite didn't form within the rocks, but is low-temperature hematite, then how did it form? Perhaps it formed some distance away from where it is now and was transported to its present location. And since 1) hematite can be produced from olivine-rich lavas and 2) there is a lot of olivine in unaltered Martian lavas, it's conceivable that low-temperature water processes could have formed this hematite -- just not in situ.

Second point: I know I've read that hematite, once formed, does not melt. If a hematitic bed of rock (formed in whatever climate and under whatever conditions were conducive to such formation) was struck by an energetic meteor (or even a basin-forming event), that hematitic rock bed wouldn't melt, it would be pulverized. Broken into pieces, smallest (dust-sized grains) nearest the impact point and larger away from the impact. Thus, it would be possible for an impact to distribute hematitic fragments within its ejecta blanket. (However, since the hematite would not melt, it would likely not accrete into spherules out of dust-sized granules within the ejecta cloud/surge. I can't imagine anything other than melting that would form the hard, solid berries we see out of hematitic particles and dust, and as has been said, hematite won't melt and therefore can't be annealed into a single solid mass from pulverized particles. And these berries are strong and erosion-resistant, they don't appear to be hematitic dust bound in some other kind of matrix.)

I am not siding with an impact origin for the spherules at this point. I need a lot more convincing before I will go that far. However, I believe there *is* a not-altogether-impossible sequence of events which which would allow for it. For the distribution to be so widespread in this area, multiple large impacts would have had to occurred into hematitic rock beds nearby the area. If the layered sulphates actually were laid down on top of berries as they sat on the surface (a process I just don't see evidence of in the MIs of embedded berries), then it is just possible that repeated impacts over time have excavated hematite, spherized the ejected granules either due to impact stresses or due to extreme erosive conditions within the impact cloud/surge, and covered the surface evenly enough and regularly enough for it to *appear* that they are uniformly distributed throughout the rock.

However, it just doesn't look like there are berry "deposition planes" within the rocks that would define the surfaces upon which they were deposited. Unless the putative impacts which distributed the berries (all at different distances and releasing different amounts of energy, thus excavating different amounts of rock and ejecting it different distances) somehow produce unformly-sized spherized pebbles each and every time, which I consider highly improbable, then I'm afraid our friend Occam won't approve.

The only thing that would make any sense whatsoever, if the berries are ejecta, is that they were ejected from a basin-forming impact partway across the planet. A single large impact event could create zones of ejecta of similar content and character that are hundreds to thousands of miles in extent, in one dimension or another. But again -- if the berries all came from a single huge impact, how did they get so uniformly distributed through the Meridiani sulphate-rich rock beds?

-the other Doug

Posted by: MarsIsImportant Jul 13 2007, 04:56 AM

Well, the distribution of the spherules was a problem that the MER team used to criticize Dr. Burt's conclusions. Yet, Dr. Burt doesn't accept that argument in opposition to impact or the others. In fact, he turns the argument right around stating that the distribution is a bigger problem for the MER team's model, because there are no major clusters observed to support the idea of spherules as concretions. Again, instead of addressing the problem with respect to impact surge--which he should--he simply says that the distrubution is an even bigger problem for the MER team's model.

We have all gone through this over and over again. I cannot arrange the arguments against impact surge better than what the MER team already has done. Dr. Burt rejects them. Yet, I think the MER team has come up with valid objections to the impact theory. That's my opinion.

I'm ready to vote in a poll.

Posted by: Bill Harris Jul 13 2007, 06:56 AM

Agreed, Mars. His argue-ments remind me of http://www.mwscomp.com/movies/grail/grail-04.htm .

---Bill

Posted by: Kye Goodwin Jul 13 2007, 03:09 PM

MarsIsImportant, re your reply 22, I agree, both the impact-surge hypothesis and the MER team hypothesis have a big problem explaining the distribution of the spherules, and both groups have been effective in pointing out the problem for their opponents while glossing over a similar problem for their own scenario. I think that the answer lies in realizing that the spherules are not an integral part of the deposit but occur only at it's surface, not the plain's surface but the entire present surface, which includes the crater interiors.

I just thought of another puzzling observation that can be simply explained by the surficial spherule idea. Both the MER team and impact surge authors believe that the spherules have eroded out of layered rock and accumulated on the surface of the soil on the plains, but the one place that we would most expect to hold accumulations of released spherules, Endurance Crater, shows no extra spherules at all. I have always had difficulty with this. The crater walls are studded with spherules and many are standing well above the rock suggesting that they are near to breaking loose. Many spherules must have already rolled from the crater walls if sufficient rock has been eroded to fully expose the spherules still in place. But where are those accumulations of loose spherules? They are nowhere we can see them, not in depressions on the slopes or at the base of slopes. The surficial spherule idea has a very simple answer: the spherules are not eroding out of the rock, so there is no need to explain why they have not accumulated downslope in Endurance Crater.

Posted by: Gray Jul 13 2007, 04:19 PM

I have two responses to this objection. First, the large drifts as the bottom of Endurance indicate that sediment is being deposited there. That sediment could easily cover many of the spherules that have eroded from the cliffs. Second, even with the deposition that is occurring, I believe there is an accumulation of spherules at the base of the cliffs.

This image: http://marsrovers.jpl.nasa.gov/gallery/all/1/p/195/1P145496190EFF3500P2415L2M1.HTML was taken on sol 195 when Opportunity was near the large rock Wopmay and near the base of the Endurance Crater cliff. I could be mistaken, but those look like spherules.

Posted by: denis Jul 13 2007, 04:50 PM

Kye,

When what looks closely at the spatial distribution of the spherules, one concludes that the plains spherules are randomly distributed at small scale, and that the crater (I mean Endurance) ones are more clustered than random. That means that the plains spherules have probably not moved from their original location, while the clustering of the crater ones is a result of their (limited ) accumulation following their release from the host rock. An other consequence is that in the frame of a surface growth hypothesis, there is no short distance interaction (soil nutriment depletion for instance) between spherules. This is contrasting with the MER team claim that the berries embedded in the rocks are more uniformly distributed than random as is expected in a concretion process (McLennan).

denis

Posted by: Kye Goodwin Jul 13 2007, 05:13 PM

Gray, Thanks for considering this. What I wrote is that Endurance shows no apparent extra spherules. The image you posted does very likely show spherules, and these are distributed thinly over the surface much as they are on the soil of the plains. What I think is missing at Endurance is any sign of spherules as scree deposits. We have not seen deposits of spherules anywhere that appear to have accumulated to a depth of more than one. On deeper soil, where trenching has been done the spherules are revealed to form a thin layer on the surface, though a few were seen at shallow depth in trench walls. In your image from Wop May's vicinity, we can be fairly sure that only a thin and partial layer of spherules is present because the bedrock is visible through the berries and soil. Here is another image from that same station that shows that bedrock is very near the surface.

http://marsrovers.jpl.nasa.gov/gallery/all/1/p/195/1P145496165EFF3500P2415L5M1.JPG

The spherules that have rolled from the crater walls could be hidden in some way but it would be reassuring to see them somewhere as a colluvial fan if they are descending the slopes.

Posted by: Kye Goodwin Jul 13 2007, 07:01 PM

denis, re your 26, Thanks. On your first point: I have noticed that spherules occur less frequently on rock than on soil. This is pretty well established for spherules attached to rock, but it also seems to be true for loose spherules. The densest coverings of spherules seem to always be on soil and I tend to think that the presence of soil is somehow causing the denser spherule populations. The causality can easily be turned around, however, and soil explained by the presence of spherules, which would reduce wind at the surface and allow soil or dust to accumulate between them. Still, I would GUESS that your clustering of loose spherules within Endurance could be caused by the generally shallow and patchy soil cover in Endurance compared with the plains, that is, a mixture of rock and soil substrates is available.
You mention limited accumulations of spherules in Endurance but I don't see any accumulations that appear to be connected to gravity movements, and I don't think that there are overall more spherules per area in Endurance than on the plains.
You write of "short distance interaction between spherules". The average distance between spherules attached to rock surfaces is much greater than the average distance between spherules loose on soil, so if the ancient subsurface concretion model is used, wouldn't a long (or at least longer) distance interaction be required to explain them? What is the approximate "short distance" you are referring to and how does it compare with the average separation of spherules attached to rock? Dr. Burt might laugh at the idea that spherules forming in a groundwater system could be controlled by nothing but the distance to nearby spherules, and I have to agree with the criticism. The MER team have been forced to propose that their spherule-building aquifer was uniformly permeated at all depths with water and solutes and that the water did not move, which is asking a lot. A surface nodule explanation isn't obviously any better at explaining the spaced-apart spherule distributions, but it does avoid (through vagueness) having to invoke groundwater and earth-like concretion formation. It may help to explain why the more-uniform-than-random distributions are clear at the surface - it is in the surface environment that spherule growth has taken place and been controlled.

Posted by: MarsIsImportant Jul 13 2007, 09:17 PM

I think Mars is throwing us another 'monkey wrench'. It might be possible that longer range interaction between spherules was in effect in the recent past.

http://www.unmannedspaceflight.com/index.php?showtopic=4397

If the CO2 ice cap at the south pole only started forming within the last 1k years, then the Martian atmosphere must have been thicker in the recent past. This is a possibility that I never considered before. So the MER team might not be as far off the mark concidering distribution as they first might seem.

Back to your idea of a some sort of surface event creating the spherules. I don't see how; but let's assume that something did happen. That would mean a drastic change in the atmosphere of Mars in relatively recent times. The only thing plausible I can think of is some sort of volcanic event. But there are no known volcanoes anywhere near Meridiani. Is it possible that some massive hydrothermal event occurred? ...something so massive that the atmospheric temperature around Meridiani reached about 300 Celsius?

We now have good evidence of possible hydrothermal activity at Gusev. Why not a much larger network at Meridiani?
(I have my doubts like probably most others reading this. I'm just brainstorming).

Edit: One thing about the hydrothermal event idea is that it didn't have to happen recently to have created the temperatures necessary for the creation of the spherules.

Posted by: Kye Goodwin Jul 15 2007, 03:18 PM

I just thought of another remarkable observation that the surficial spherule idea might help to explain. The MER team has estimated that about 2% of the total rock volume of the Eagle Crater outcrops is made up of spherules. Here is a pancam image from Endurance that shows large numbers of spherules clearly against a band of brighter rock:

http://marsrovers.jpl.nasa.gov/gallery/all/1/p/291/1P154016968EFF37MIP2274L5M1.JPG

This high density of spherules is surprising somehow. It asks a lot of the proposed aquifer, which has to be at least as deep as Endurance Crater and without significant water movement in the MER team scenario. How has it supplied the concretion materials in sufficient quantity to the entire volume of rock? If the spherules are present only as a surface concentration then the large numbers we see are not so remarkable. It is a weak line of argument, but I thought it worth adding because I think it has struck many observers intuitivlely that the spherules are strangely numerous in this rock.

I think that there was a fork in the road very early in the interpretation of Eagle Crater that went by too fast and has never been revisited. At pancam scale, such as in the Endurance image above, one might imagine that the protruding spherules are stuck to the surface of the rock. When more closely examined with the MI it is clear that some spherules are embedded in the surface of the rock. From this observation the conclusion was reached that the spherules occur throughout the bedded sediments at densities similar to those we see at the surface. I think that this decision should be revisited. It is at this point that the paradoxes of the spherules distribution and relation to the bedding are created. If we remain skeptical that the spherules are present throughout the deposit, then the contradictions never appear. I think that for this reason alone the surficial spherule idea is worth investigating.

Posted by: djellison Jul 15 2007, 03:41 PM

How do you make hematite rich spheres sat on top of olivine rich soil? The two are essentially mutually exclusive minerals. The existence of one makes a VERY strong case against the formation of the other. You're going to have to some up with something extraordinary to do that.

You've still not touched the fact that the spherules are different and/or absent in different places.

And the earth analogues we've seen of concretions show a lot of concretions in not a lot of rock - the ratio is certainly similar, if not higher, than the one here.

And - if you're proposing the surface formation of the spheres at the same time as the surface formation of sulphate rich rock - why is there not sulphate rich rock everywhere? Why is there some forming and hiding spheres to a depth of a few mm here (pointing straight down at a piece of outcrop) but none there ( pointing to a patch of soil a metre to the right).

Surface formation has a lot more issues to tackle than any other theory I've seen. It seems like you're trying to solve one problem, by creating many more.

Doug

Posted by: Kye Goodwin Jul 17 2007, 02:31 PM

Doug, re your post 31, in the same order: I am not proposing that bulk liquid water is involved. The jarosite and nanophase iron-oxide crystals at Meridiani needed water to form, but ample water would have altered them further. Olivine sharing the surface with water-altered minerals might similarly be an indication of water activity that is limited in some unknown way. I don't buy the idea that there was water chemistry happening billions of years ago that stopped and has been preserved ever since by totally dry conditions.

The spherules are different in different places at kilometer scale, but that fact could be interpretted in many ways. (We saw few large spherules near Erebus, but they seemed to be replaced by many tiny spherules.)

The trouble with trying to compare the frequency of occurence of spherules in rock at Meridiani versus Earth is deciding how much rock to include in your calculation. What is the average frequency of Utah spherules if the entire sandstone formation is included as the denominator? I think that the spherule frequency that is suggested by what we see at the surface at Meridiani is more like that of a concentration of Utah spherules where groundwater conditions were favorable than it is like the average in an entire formation.

I think you are asking if mineral is accreting on rock surfaces at Meridiani, why isn't it accreting on soil surfaces. I don't know. The fate of deposited dust on Mars surface is highly variable. It interacts chemically with some surfaces and is relofted from others. Because of the large difference in thermal inertia the microclimate of soil is very different from rock at times in the daily cycle.

Of course I need the Alien Planet Pardon to discuss the topic of surface spherule growth at all. Part of being ultra-conservative in our interpretation of Mars is not ruling out anything prematuely. If a hypothesis can simplify the picture a lot by proposing a previously unknown process then we should consider it.


Here is another way to consider the surface spherule vs deep spherule question:

Let’s review the evidence that the spherules are integral to the layered deposit, that is that they are present throughout at frequencies like we see at the surface:

1. Many spherules are visible partially embedded in the rock, and the RAT has revealed that some are fully embedded.

That’s it. There is no other evidence that the spherules occur throughout the rock. If you think I missed a line of evidence, let me know.

Now how about the evidence that the spherules are not integral to the rock:

1. The spherules do not disturb the fine bedding in the rock.
2. The spherules are distributed in a way that shows no correlation with the bedding or contacts in the rock.

There may be more evidence on this side but these two lines are pretty persuasive. Considering that we are on an alien planet and do not know how to properly weight these indications, I think that it is premature to conclude that the spherules are present throughout the layered rock.

Posted by: paxdan Jul 17 2007, 03:29 PM

An engineer, a physicist, and a mathematician were on a train heading north, and had just crossed the border into Scotland.

* The engineer looked out of the window and said "Look! Scottish sheep are black!"
* The physicist said, "No, no. Some Scottish sheep are black."
* The mathematician looked irritated. "There is at least one field, containing at least one sheep, of which at least one side is black."

Posted by: djellison Jul 17 2007, 03:47 PM

Until you can come up with ANY viable means by which they could form on the surface - it's not premature at all.

I'm not going to try and defend or explain the MER line of geology at Meridiani - but have you considered asking them, or searching for references regarding the interaction of concretion formation and rock layering. If the best you can do to explain your own theory is to find fault with another one - you're going about it the wrong way. Finding fault with theory A does not make theory B any less or more correct. Focus on YOUR theory with the evidence we have.

Simply looking at the laymans-terms evidence we've seen - I have not seen you tackle any of the major issues involved here - and you've got to. It's that simply. You can't keep arguing for this theory whilst continually ignoring the big issues sat on top of it (which you have been for a long time)

The berries-on-stalks we have seen at places like Fram are indicators surely that the 'muffin' is eroding (and leaving berries behind as it goes) , not being deposited. How can you form a berry in mid air and then form a connecting rod of sulphate rich rock to connect it to the rest of the rock? Did the rock know to form out to a point and then magically grow a berry on top?

If you're saying they're forming, today, on the surface, then why are they different not over km scales - but METRE scales - from the top of endurance to the bottom - a distance of <20m and a height of 5m. If you're aguing they're forming today - they why only here and nowhere else. Why not other equatorial regions of similar elevation?

How can you explain that over a distance of 1cm, you go from the formation of hematite on top of olivine soil, to the formation of hematite which is then burried by sulphate rich rocks?

How can you explain the composition of the rock you say is forming today - is different from the top of Endurance to the bottom? Whatever water vapour etc you're saying is forming this stuff is going to be the same from Tennesse to Axel Heiberg. But it isn't. Nor, simply at face value, does this stuff look like it's forming today. If it were, it would be the same look everywhere - but it isn't. Just in a few metres of Burns cliff it looks different from top to bottom, which indeed we see in matching APXS data. It it were forming today - would it not all be the same? Would it not have hidden the cross bedding? Why, if it's forming today, do we see this bright band at Victoria?

http://marsrover.nasa.gov/gallery/press/opportunity/20040818a.html - look at the MI's, look at the graphs. How can this be happening today?

I'm not trying to have a go at you - I genuinely want you to try and tackle these questions because for your theory to become anything other than against the mainstream hand waving ( which is where it's at currently ) - you've got to start answering these sorts of questions.

Doug

Posted by: Kye Goodwin Jul 19 2007, 05:29 PM

Doug, Thanks for removing that off-topic post.

Regarding your post 34, Sorry I do not have all the time that I would like to have these days and just trying to read all the content pouring into Dr Burt's thread takes up much of it.

You say that I do not "tackle any of the major issues", but I think that I am cutting to the heart of the matter. The spherules do not distort the bedding layers and are distributed in a way that shows no correlation with bedding layers or contacts in the rock. These are the key observations that have led the MER team to propose their concretion hypothesis. They strongly suggest that the spherules were not deposited along with the layered material. These two observations have forced the MER team to a concretion hypothesis that seems extraodinary to many and is a such a bad fit with Earth concretions that Dr. Burt can savage it at will. (Why the shape invariance, size limit, and distributions that in no way suggest growth from materials in moving ground water?) I give the MER team credit for continuing to take these two observations seriously. The impact spherule theory just ignores them.

Posted by: djellison Jul 19 2007, 05:47 PM

You're avoiding it. You couldn't be avoiding it more if you tried. You're avoiding the fundamental point of your theory..

how

In light of all the evidence I've shown ( stalks, different surface elemental compositions, different spherule sizes and distributions, etc etc)... the only thing that could be considered the heart of the matter is...

how?

Until you tackle that issue - we're all wasting our time. Sorry to be so blunt about it - but that's the truth.

Doug

Posted by: MarsIsImportant Jul 19 2007, 05:55 PM

To be fair, you are tackling the distribution problem with a unique approach. You are suggesting a surface location for the origin of the spherules. Let's assume temporarily that that is correct. What process created them?

My understanding is that you suggest the spherules were embedded into the surface through accretion of some sort. But I don't understand your proposed origin of the spherules themselves given your hypothesis. What process created them and gently laid them down onto the surface?

Edit: Doug and I are really asking the same question. We just expressed it differently.

Posted by: djellison Jul 19 2007, 10:35 PM

Interesting paper regarding erosion rates :

http://trs-new.jpl.nasa.gov/dspace/handle/2014/40227

You have to explain why this entire paper is utterly wrong to begin making sense of your theory Kye. You've got to stop pretending a theory can hang on a contraindication but at the same time ignore it's own contraindications - such as that paper.

Dou

Posted by: Stu Jul 19 2007, 10:46 PM

The conversation was overheard in a neighbouring carriage, by a member of UMSF and an ESA scientist, both travelling to a conference in Edinburgh.

"I want pictures of those sheep! Now!" said the UMSFer impatiently, booting up his laptop ready to attack the sheep images with Photoshop, eager to enhance the colour and texture of every strand of wool on their bodies.

"I have the pictures here," smiled the ESA scientist, looking at his own laptop, before adding "but I'm not showing them to anyone else..." and flipping the screen down.

Posted by: Kye Goodwin Jul 19 2007, 11:24 PM

Doug, Yes, "How?" is now the heart of the matter if you have followed me this far. How could the spherules be surficial? I am advancing a sub-aerial concretion hypothesis, but others might think of other possibilities. I am not a chemist and cannot offer a detailed chemical model but I can make make some general points toward the possibility that hematite spherules could form spontaneously under recent or current surface conditions.

Many aqueous chemical processes have been proposed to take place in the Martian surface environment under conditions like the present conditions. There is a long tradition of surface-weathering discussion, from Viking weathering pits and Pathfinder rock-coatings to many phenomena discovered by the MERs. I could post a whole bibliography in time, but here are two. This Yen et al paper introduces the idea of weathering facilitated by a daily water cycle:
http://www.lpi.usra.edu/meetings/lpsc2005/pdf/1571.pdf
This Yen et al paper suggests a roll for recent water activity in the formation of rinds at Meridiani:
http://www.lpi.usra.edu/meetings/lpsc2006/pdf/2128.pdf

My point is that scientists think that a variety of aqueous chemical processes are probably happening on the present-day surface. Is there a particular reason to think that hematite formation could not be among these processes? There is plentiful magnetite in the ever-renewed airfall dust. This could be oxidized to hematite by a spontaneous (energy-yielding) reaction if oxidant is present as believed from the Viking results. A chemist would have difficulty setting up the assumptions for a hematite-forming process because so little is known of Martian soil chemistry or the planet's diurnal water cycle.

If we accept that it might be possible for hematite to form, why would it form as tiny spheres? Why would it be sharply localized in any form? I can't offer any reason for the sphericity or localization.

OK, I admit that this is not a sophisticated or close-to-complete model, but I haven't resorted to mysticism. Maybe a chemist will comment. I think that I will continue to consider the surface-spherule idea because it is a possiblity that would explain much simply.

Posted by: djellison Jul 20 2007, 06:59 AM

No - not surface - the near SUB surface - and in one case speculated as being places that have been recently exhumed.

They're talking about alteration by thin films of water. You're talking about the deposition of hematite and sulphate rocks. If you're getting water deposition from frost - then it's pure water - not the sort of water that could leave rocks behind.

Dominating Meridiani is erosion. It's clear to see from the imagery. How you can propose that the surface is growing, and burrying Berries - I just don't know.

Doug

Posted by: Aussie Jul 20 2007, 09:56 AM

Kye,
Could you please provide a model for your theory of sub aeriel deposition and how this can result in spherical hematite products embedded withing the matrix. Look, I will even leave the accretion as opposed to erosional argument aside. Just explain how grey hematirte can form into spheres on the surface. Please don't reference weathering rinds or desert varnish, we are talking about spheres. and hematite. If you have a valid model then this thread is a valuable entity. If this is just against the mainstream arm waving then perhaps we should stop wasting time.

Posted by: Kye Goodwin Jul 20 2007, 03:28 PM

Doug, re your post 41, Yen is referring to the surface environment in that paper in the sense that the activity he describes must be within the diurnal thermal skin depth which is generally agreed to be no more than a few centimeters. The water from frost that he suggests as an agent of chemical weathering falls on the surface each night and the heat that moves it around comes from the sun shining on the surface. I include the top few centimeters in what I am calling the surface environment.

Aussie re your 42, There are many ways to work on this problem besides starting with a detailed chemical model. Were science to become convinced that hematite spherules have formed on the surface then chemists would soon find models to explain how it might have happened. The necessary reagents are plausibly present and other aqueously catalysed processes are probably happening in the same environment. I can't yet explain why spheres would be the result, but as Dr Burt has pointed out, the MER team concretion theory does not explain the sphericity either. I'm afraid that the impact-spherule idea is the only theory so far that can explain the sphericity.

It occurs to me that I should try to find out more about the non-spherule instances of hematite that have turned up at Gusev. One was a possible hematite coating on Mazatzal (see the first Yen paper in my post 40), the second was Pot-o-gold, and the third was Halley at Low Ridge. Do we know enough about any of these to say if the hematite was in the grey or red form?

Posted by: djellison Jul 20 2007, 06:09 PM

You've had ten days to bring some sound science to your theory - and have avoided or found it impossible to do so. You've repeatedly avoided ignored the difficult issues around it.

I'm going to take a leaf out of the BAUT rule book and put a time limit on this thread. I'll give it 5 more days – and then close it. Long enough for you to bring some science to it if you're ever going to, but short enough so we can all stop wasting our time if you're not.

If you're looking for somewhere to carry on talking about it thereafter, I would highly recommend the BAUT forum - as it's exceptionally tolerant of theories that are against the mainstream, but within well established rules.

Doug

Posted by: Kye Goodwin Jul 21 2007, 03:26 PM

Paxdan, re your 33, That's funny, Thanks. We have crossed the border to a far stranger place than Scotland. On Mars the mathematician's humourously cautious approach may be the most appropriate.

Doug, I do this for pleasure, and I've found that deadlines tend to spoil the fun, so your proposed deadline just isn't going to work for me. You have been keeping this thread alive with your keen interest. If there isn't any further interest by others this is likely to be my last post here. There are lines of evidence which I have not discussed suggesting that the spherules may be surficial, but I am not in any hurry.

In the fall of 2004 I read the original Brine-splat paper and soon thought that the Meridiani layered deposit had been well and simply explained. Impact-surge is such a good idea that I expected to be reading about it in the newspapers within weeks. I did read it in Nature a year later and have watched the impact surge idea slowly gain prominence in the discussion. The MER team now regularly addresses it as the primary alternative to their own work. It seems that you have decided to cut off Dr. Burt's thread. It is hard to understand why you wouldn't want the central debate about Meridiani to take place on your site.

I would be happy to hear from anyone with friendly or constructively critical comments about the ideas I have raised here. I haven't got very far yet with my research on the three occurences of hematite detected at Gusev. I have a paper copy of "Water alteration of rocks and soils on Mars at the Spirit rover site in Gusev Crater" from Nature July 2005, Haskin et al. It includes the detail that the coatings on Mazatzal "contain the only occurrence of CRYSTALLINE haematite detected to date on the basaltic plains of Gusev" (emphasis mine). The source of that is referenced but I ran out of dimes at the library that day and failed to copy the last page. If anyone is ahead of me on this, just what sort of crystalline haematite was detected on Mazatzal? This info-pauper will continue the search. This question may be pertinent to the impact spherule hypothesis because if grey hematite has been found in a form other than spherules it would suggest that a Mars process other than impact may be able to create grey hematite.

Posted by: djellison Jul 21 2007, 04:13 PM

Indeed - Dr Burt agreed it was the right thing to do - it was going in circles and getting no futher. The same is true here - but given that this thread has been going for less time, I thought I'd give it a little longer before bringing it to a close.

In both cases - the threads have been more of a cyclical soap-box rather than scientific debate - and that's not something I want at UMSF.

Doug

Posted by: tglotch Jul 21 2007, 07:15 PM

Kye,

The oxidation reaction that you hypothesize would not produce hematite, but rather maghemite. High temperatures (such as might be produced by impact) could oxidize the magnetite to hematite. However, as I think I've mentioned before in other threads, hematite formed by the oxidation of magnetite produces an infrared spectrum that is inconsistent with what is seen by TES and Mini-TES.

Posted by: Kye Goodwin Jul 22 2007, 01:33 AM

tglotch, re your post 47, Thanks very much for your response. My amateur attempt at describing at a hematite creation process has not produced a good model. May I call upon your expertise to answer a few questions on related topics?
I have been wondering what we know about the three occurrences of hematite at Gusev Crater: the hematite-rich coating on Mazatzal and hematite detected in Pot-o-gold and Halley. Do we know if the crystal structure of any of these hematite minerals resembles that of the Meridiani spherules?

Apologies for the following questions. They are too general and also leading, but I hope that you might comment.
Is there any way that hematite could form at Meridiani from the available minerals in the dust, soil or rock under climate conditions that have prevailed relatively recently in Mars history? Could such a process produce the type of hematite crystal structure that the spherules display? If grey hematite could form in a cold sub-surface aquifer, is it conceivable that slow limited aqueous processes on the surface could accomplish the same result over a longer period of time?

Posted by: tglotch Jul 23 2007, 07:56 PM

Kye,

The occurrences of hematite at Gusev were detected by the Moessbauer spectrometer and not seen by Mini-TES. This implies that the hematite there is not coarsely crystalline like it is at Meridiani.

As for Meridiani, we don't know the exact mineralogy of the dust, but we know the Fe-bearing phase is magnetite. See my above post for my take on the magnetite-to-hematite transition.

My view on the hematite formation at Meridiani can be summed up thusly: thermal IR data from TES and Mini-TES rule out a high-temperature formation mechanism. In addition, there is no reason to pose an exotic formation mechanism under current conditions when there is plenty of evidence for past aqueous (however short-lived) activity. Breakdown of Fe-sulfates in the outcrop is to me the most reasonable mechanism to form the hematite spherules.

Posted by: Kye Goodwin Jul 24 2007, 02:39 PM

tglotch, Thanks for that information about the hematite at Gusev (your post 49). I guess that it doesn’t have any obvious implications for the origin of the spherules at Meridiani.

I am seeking a low-temperature formation mechanism that could operate under recent Mars conditions because for me an “exotic” process would be one that requires a warm Mars. It is still an extraordinary claim that Mars once had a climate that would allow liquid surface water or near-surface groundwater. The MERs have added no evidence of persistent surface water. They have discovered overwhelming evidence of water-catalysed chemistry, but no structural evidence of beaches, lake-bottoms, channels or water-tables that put the chemical activity in an Earth-like context. Those are very likely impact sediments at Meridiani.

We have seen far too much evidence of water chemistry for it's origins to lie mostly in a brief warm period early in Mars history. In the Columbia Hills the evidence of aqueous chemistry is complex and mystifying, so much so, that it is now being explained as water interacting with volcanism, but again there are no clear signs of bulk liquid water. Volcanically heated waters must be fairly rare but I think that much of Mars surface will turn out to be as chemically complex as the Hills. Water chemistry has been happening there in slow Martian ways over the whole history of the planet.

Posted by: djellison Jul 24 2007, 04:21 PM

....in your opinion.

It's time to bring this thread to a close.