"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]

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.

[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