"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.

[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.