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Regarding the "Basal Surge" hypothesis, What really did create the Meridiani layered deposits?
post Mar 21 2006, 12:29 AM
Post #31


Actually, the MER team's model -- or the version of it which says that the second exposure of the Meridiani material to water was to non-acid groundwater -- also explains the creation of the Blueberries much better than the two basal surge theories, since most models of Blueberry creation call for dry ferric iron sulfates (produced by a previous exposure of minerals to acid water) to be mixed with nonacidic water that makes the iron precipitate out again as concretions of hematite (or goethite, which can later dry up over the eons of Dry Mars' history to turn into hematite). See Ormo's LPSC abstract (#1356), as well as the various reports of what's going on at the strange environment of Rio Tinto in Spain. This would also seem to explain why locations with Blueberries seem to be a lot rarer on Mars (judging from Mars Express' and MGS' maps) than locations with just plain sulfates -- simple exposure to acid water is enough to produce sulfates, whereas a locale has to be exposed to acid AND THEN nonacid water to produce precipitated hematite.

QUOTE (AlexBlackwell @ Mar 21 2006, 12:18 AM) *
In other words, you've covered yourself by picking every plausible model; therefore, you can claim that you were, ultimately, correct? I like that stock broker-like approach ("The market may go up, or down, or stay the same"). biggrin.gif

Alex, this is getting tiresome. What Squyres said was just what I said he said: he showed me that I had seriously misinterpreted what the MER team was saying, and that they really support a view virtually identical to my "fourth" listed theory. My only consolation is that he says that the basal-surge advocates have also been totally misinterpreting what the MER team really said.
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post Mar 21 2006, 12:39 AM
Post #32


QUOTE (BruceMoomaw @ Mar 21 2006, 12:29 AM) *
Alex, this is getting tiresome. What Squyres said was just what I said he said...

What's "getting tiresome," Bruce, is your penchant for strawman arguments. I never questioned "[w]hat Squyres said," so stop insinuating that I did.

I was only pointing out that, by your own admission, you laid out four models from other workers. And despite your "misinterpret[ion of] what the MER team thinks really happened at Meridiani," your "'fourth' listed theory" actually does agree with them; in fact, it was, in your own words, "virtually identical."

In other words, you were ultimately right (once again).
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post Mar 21 2006, 02:52 AM
Post #33


What you implied was that I had left myself an out for saying that either of two theories (or maybe four, since I don't fully understand your argument) was right. What I actually did was say (falsely) that the MER Team itself believed one theory, but that I wondered whether another one might match the facts better instead. What I actually found out was that I had been totally wrong in saying that they agreed with the first theory; they actually did agree with the second one. This is hardly the same thing as saying that I deliberately left myself an opening for saying that I was "right" in any case -- what it shows is that I was right on one thing and totally wrong on another. Please don't accuse me of being more egotistical than I actually am.

For whatever it's worth, I hadn't even contacted Squyres yet to ask him about this (although I probably would have tried to do so at some point in the next few days to straighten up my understanding of the whole situation). Instead, somebody else who reads this site (I don't know who) contacted him and quoted me to him, whereupon he got directly back to me.
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post Mar 22 2006, 05:43 AM
Post #34

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I promised to post some notes regarding Professor Grotzinger's comments about the blueberry spatial distribution. He noted that the berries were dispersed, not organized along bedding planes or cross-strata, as would be expected in the basal surge model. They did a Monte Carlo simulation of the berry distribution, and it was exactly what one would expect for concretions formed by molecular diffusion processes.

I might also note that he addressed the trough crossbedding and said, as others on the team have previously said, that the scale of the bedding or lamination is important, and the scales seen in Meridiani are a better fit with an aqueous origin than a surge origin. He pointed out that the gravitational constant was expected to have an affect on the scaling, but in their determination it was not a large afffect between Earth and Mars. I hope I captured that accurately, but I think that is what I heard him say. cool.gif


I'm not a Space Fan, I'm a Space Exploration Enthusiast.
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