"Could the Meridiani Spherules be Surficial?" Options

[Kye Goodwin]

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.

[djellison]

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

[Kye Goodwin]

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...00P2956M2M1.JPG

http://marsrovers.jpl.nasa.gov/gallery/all...00P2956M2M1.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.

[MarsIsImportant]

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?

[djellison]

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.

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

[Kye Goodwin]

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.

[Kye Goodwin]

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.

[Pavel]

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.

[Kye Goodwin]

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.

[Kye Goodwin]

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.

[djellison]

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.

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)

[MarsIsImportant]

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?

[Bill Harris]

I do not need to prove that accretion is taking place at Meridiani, but only to raise doubts that it might be.

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

[Kye Goodwin]

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.

[climber]

...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.

...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?