"Could the Meridiani Spherules be Surficial?" |
"Could the Meridiani Spherules be Surficial?" |
Jul 10 2007, 04:37 PM
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Junior Member Group: Members Posts: 42 Joined: 2-July 07 Member No.: 2646 |
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. |
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Jul 17 2007, 02:31 PM
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Junior Member Group: Members Posts: 42 Joined: 2-July 07 Member No.: 2646 |
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. |
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