My mind has not changed, just because I ceded one point of contention. The professor did not change his mind when he ceded one to me earlier. I never expected him to change his mind about his surge hypothesis. I also anticipated his response of the possibility of erosion of an ejecta piece in the area of home plate as an explanation for the silica sand found recently.

Just because something is deemed possible in one particular respect does not mean it is probable. It only adds a small amount of credibility to an alternative argument. It simply raised the scenario from the realm of impossibility in my mind to one of possible but unlikely. I'm sure the Professor feels the same way about his concession to my point. Yet, such concessions are expected, else this issue would not be given the room for argument on this forum.

A straw poll (and given the nature of forum software, such things are easily done ) of the two main rock formation theories would be an interesting thing. I think it's only fair to give HDP's hypothesis more airing time, and then we could do a poll to see which camp people fall down on.

Doug

Yes, Professor you have addressed the topic before. But you concentrated on how features observed coincided with those predicted by your surge hypothesis. That seems to make your scenario somewhat possible in those respects (I'm temporarily discounting objections for other reasons). But those same characteristics of those features also coincide with the MER team's explanation. Differences in interpretation of the same features cannot distinguish between the two competing theories.

What I'm looking for are distinguishing characteristics of your explanation that would not be present given the MER team's wet Meridiani scenario...or vice versa. This would offer a test to determine which hypothesis is more probable. A predicted distinguishing feature that can be observed would turn this argument away from a 'he said she said' like confrontation.

dBurt – back to the sulfates: You’ve stated often that you have a problem with the latest MER scenario that: “requires maintenance of a highly acidic aquifer in rocks containing basaltic materials” (unpublished response to response Knauth, Burt and Wohletz). You feel the neutralization capacity of the basalt wouldn’t allow this imbalance. You reference Zolotov 2005 to support of your point. However in a recent abstract of Zolotov (Lunar and Planetary Science 2007) the point is made that “acid weathering on early mars probably player a larger role……”. Apparently he doesn’t have a problem with longer duration acidic conditions. As you have pointed out by the presence of neutral salts, neutralization eventually occurs, but after what period of acidity? He also discusses the role of large impacts as a cause of acid weathering. Another abstract by Benison et al (Seventh Int. Conf on Mars) discusses the geochem and mineralogy of mars and makes a good case for extended acidic conditions even in the presence of mafic rocks. Do I hear the sound of rock hammers chipping away at this once solid foundation ?

"the other don"

HDP Don re#190,195

Thanks so much for your input. Looks like our questions encounter a resonator with Dr Wohletz . I would like to know to which data on berries sizes he is refering to. I will try to figure out what is the significance of his SFT distribution parameters (phi, dispersion), as compared to our more conventional ones (mean, skewness). What impress me is his statement for a signature of an accretion scenario.

denis

Let's just assume for an instant that the impact surge hypothesis were correct (that's a temporary assumption).

The hematite spherules are like hail stones. Shouldn't they create some type of minor bomb sagging evidence within the layers of deposits? This should be observable with the Micro-Imager on the rover. I know of no such disturbance within the layered deposits. Just because such a disturbance has not been identified yet, is no indication of whether they are actually there--unless somebody actively searched for such evidence. Perhaps this was the basis for the MER team ruling out the volcanic surge process in the formation of the spherules.

If I remember correctly, somebody stated there was no indication of disturbance within the layers caused by the spherules. Doesn't that highly suggest that the spherules were created in place? If the spherules would not create a disturbance in the layers during the impact surge, then why not? What is so different about an impact surge from a volcanic surge that would prevent such disturbances?

Edit: http://volcanology.geol.ucsb.edu/saltlake.gif

http://volcanology.geol.ucsb.edu/hydro.htm

"Bedding sags form by the impact of ballistically ejected bombs, blocks and lapilli upon beds capable of being plastically deformed. They are common in hydroclastic deposits of many maar volcanoes, tuff rings and tuff cones. Beds beneath the fragments may be completely penetrated, dragged down and thinned, folded, or show micro-faulting (Heiken, 1971). Deformation is commonly asymmetrical, showing the angle and direction of impact if three-dimensional exposures are available. These differ from dropstones in glacial environments in that dropstones fall perpendicular to the bottom, symmetrically indenting bedding and rarely, if ever, penetrating."

The spherules would be the lapilli in this case.

MarsIsImportant - Do dig out that evidence please, as you did so well for the silica-rich soil. In the Navajo and Page Sandstones, hematitic nodular clumps up to meters across weather out as readily as individual concretions - no digging necessary. More readily, in fact - they form erosion-resistant benches. (I always prefer to cite observational evidence, rather than my general predjudices about how things ought to behave.) Your second argument is that some sort of "quick change" must have stopped the process that formed them. If so, why did it apparently stop at exactly the same time uniformly over the entire 100's of square kilometers of Meridiani - or (using direct observations by the rovers) the more than 10 kilometers of Oppy traverse, including rocks many meters deep?

What kind of "magic process" did you have in mind? I can think of no terrestrial analog offhand, or anything implicit in the extant Meridiani model that would allow it (one of my numerous problems with that model). Remember that concretions grow many meters deep in the rock, cutting them off from any conceivable weather variations. You can't stop them with a freshwater influx, because that would dissolve all the soluble Mg-sulfates that cement the rock (although such an improbable dilution is how the MER team hypothesis suggest that the hematite replaced jarosite in the first place). Also, the brines would never mix - the freshwater would sit essentially forever on top of the salt water, as in terrestrial coastal areas (another problem I have with the MER team hypothesis). Your "magic cut-off process' reeks of a 7th dead grandmother to me (i.e., rather super-special pleading), especially if you have no examples in mind for a possible process.

Next time ask me a specific question - then I probably won't ask you one.

--HDP Don

denis - I told you everything I know. I presume it is data he pulled off the web links in your original post (#181). Contact him for more info (although he may read this eventually).

HDP Don

Absence of evidence is not evidence of their absence. But even if those clusters are not there, that simply means it is a Martian mystery. Mars is not Earth.

If there are no major clusters at Meridiani, your alternative has even larger obstacles to overcome. The spherules must have been created in a low temperature environment. Kye pointed out this source for that supposition and it makes a lot of sense. It is only one piece of evidence; but it is strong.

http://www.gps.caltech.edu/~tglotch/glotch_fresnel.pdf

Edit: Sorry for jumping around my thought processes, but...

There is also no apparent asymetrical distortion within the bedding layers around the individual spherules. That should be another problem for the impact surge hypothesis. But then again. Mars is not Earth. It has less gravity. So Absence of evidence is not evidence of their absence. We need to look harder in an effort to be sure we didn't miss something.

Meanwhile, I'll do my best to dig up more evidence. And if I stumble onto something that supports the impact hypothesis, then I will share it here. It doesn't matter to me what the truth is; I'm just searching for it.

The server having been overloaded temporarily, I just deleted a duplicate post. That leaves me space to mention:

Why doesn't someone ask me if the impact that formed Victoria Crater produced a surge? (The one-word answer would be yes. Expounding, Oppy must have driven right over it, given that there's orbital evidence that some remains, and not recognized it.)

--HDP Don

Other don - Misha Zolotov (a colleague in SESE at ASU) has heard me give various talks on impact surge perhaps more times than anyone alive except Paul Knauth, and he is beginning to listen. His original (2005) statement that we cited still holds - impossible to maintain acid groundwater in a basaltic regolith (simple common sense, although he did some calculations, and others have done experiments). His LPSC abstract this past March took what I had said about impacts into abundant Fe,Ni-sulfide deposits (the abundant sulfide deposit idea originated with Roger Burns - we just added impacts, as in my mine dumps article) and about various gaseous sulfur species, in addition to steam in the surge cloud (also mentioned in my mine dumps article) and proposed a great deal of post-impact acid rain - a catastrophic flood of acid. He recognizes that this acid soon would be neutralized. This suggestion does not require target sulfides, BTW - only sulfates, and in fact it was made long ago w.r.t. the dinosaur-killing impact at Chicxulub Crater, Mexico, where the target rocks were rich in Ca-sulfates. The "catastrophic acid rain" suggestion is probably irrelevant for Meridani, where there is absolutely no sign of surface runoff, such as a catastrophic rain would produce (and the MER team therefore, quite reasonably, left rain and surface runoff out of its model). Using Occam's Razor, we also left it out of our impact model (although it certainly had occurred to us too). Sulfide weathering or acid steam condensation (also in McCollom and Hynek's volcanic surge model - abstract #3257 at Friday morning' session in Pasadena) seem completely adequate.

Relevant to Benison, D.K. et al. in Pasadena (I presume you are referring to #3376?), what strikes you as particularly Mars-like about those acid lakes? Is it that they appear to be chloride-dominated, unlike the surface of Mars? Is it that the hematitic concretions look like normal concretions, unlike the berries? Is it that by far the dominant salt precipitated is the least soluble one, gypsum, which forms pure white effloresecences, which can be picked up by the wind (very locally only) and forms white dunes? (Unlike the most soluble Mg-sulfates that dominate Meridiani.) Is it that the deposits are rich in kaolinite and other crystalline clays, as might be expected (and that presumably you'd find typical playa lake beds of clays if you trenched them), unlike Meridiani, which utterly lacks lake beds or crystalline clays? Is it that acid persists in schists and amphibolites - regional metamorphic rocks probably utterly lacking on Mars (although they might exist somewhere very, very deep inside Mars)? Is it that they specify no source of acid (but other literature specifies constant replenishment via sulfide weathering - as we propose, following Burns). I could go on and on, but perhaps you get the idea. Yes, if you cut it off from any contact with a basaltic regolith, or wind-blown dust or sand, and provide an unknown surficial source of acid (e.g., volcanic acid mist or impact-related rains), you might form a very temporary acid evaporite lake on Mars - but then you might expect to see some signs of there having been a lake. Where is it? (Meridiani is very large.) If an alien civilization had colonized Mars, they might have built monoliths, but where are they? As I concluded an earlier reply, many, many, many things are theoretically possible for Mars, including acid lakes and little green men, but please, please specify your evidence. (Jarosite is only a mineral, which usually forms via sulfide weathering on desert mine dumps or in gossans - which is how Roger Burns suggested it might form on Mars. Us too.) Thanks.

BTW, I think there's ample evidence of impact cratering on Mars, ample evidence that impact cratering produces size-limited spherules of various types, commonly enriched in Ni (as for Chicxulub spherules), and ample evidence that surge deposits emulate those deposited by wind and water. There's also every reason to expect both abundant spherule-containing surge deposits on Mars and their preservation until the present. What other evidence would you like? Note that a model NEVER constitutes direct evidence of what happened - only of what might have happened. Also remember w.r.t. models - GIGO. Also remember Occam's Razor, as restated by Einstein (choose the simplest hypothesis that explains everything). The MER team hypothesis, in addition to being the most convoluted imaginable, fails, IMHO, to account for all the evidence (athough to give them credit, they really, really tried). Ours does, so far as I yet have learned.

Sorry to rant - you seem adept at pushing my buttons. And keep chipping away - I'm truly grateful for your efforts.

HDP Don

Dr. Burt, you nailed it. That is precisely why I have tried to stay out of this debate, in spite of my desire to rant and rave about various points. By forcing all of this discussion into this one thread, it has become a tangled mess of competing and disparate ideas. It seems to me that breaking specific conversations out into separate threads in the Mars topic would provide a natural order to this brawl, allowing one to more clearly weigh the merits of the indivdual contributions. There have been some very insightful comments made as well as (dare I say) a few clueless ones. I am only suggesting that we should create some order from this chaos.
...One more thing...did the impact that formed Victoria form a surge? ...without a doubt, and the MER team has already announced that they intend to investigate a proximal contact from that event as soon as they are able to command this little robot to enter the crater.
That would be fun, and maybe more fun if we could see which way we each voted.

MarsIsImportant - You are correct that absence of evidence is not evidence of absence. On the other hand, Oppy has been driving over spherules for 3.5 years, along a traverse of over 10 km, and has imaged literally millions of them. So we have a pretty good statistical idea of what they are really like - see yesterday's posts. I could show you more variation in 10 minutes, over 10 meters of outcrop, sampling only a few hundreds of concretions, anywhere on this planet, I dare say. Certainly that's true at the sites that have been cited as Mars analogs (concretions in the Navajo and Page Sandstones of N. Arizona and S. Utah).

Statistically, the blueberries are like flipping a coin, and getting 500 heads in a row. You could always argue that the next flip might give you a tail, but at some point you have to suspect that somebody might be pulling a fast one on you - i.e., that they handed you a two-headed coin (heads on both sides). Let's just say that at this point I'm statistically pretty confident that you could flip that coin for the rest of your life, and never, ever, come up tails. My co-authors and I early on suspected that Mars might be pulling just such a fast one on Oppy and its team, so we tried to come up with an alternative hypothesis. Can you conceive of a two-headed coin, even if you've never encountered one? Time to check it out, don't you think?

I have reread the Glotch et al. article that you cite (I did so when you mentioned it on the other thread). You apparently fail to understand just what it is they are claiming. Not my field either, of course, but I think the key point is understood by looking at their Figure 10 on the last page. All that they claim to have DISPROVED by spectroscopy is a completely random orientation of platy hematite grains - this "A" is a straw horse, unreasonable to anyone who knows crystals. What they claim to have PROVED is "B" - that the c-crystallographic axis [001] of the hematite flake is radial to the center (in other words, that the flakes are arranged like those in a cylinder of paper you would get by rolling it up). This is the way a concretion might grow - but it is also the only way that an accetionary lapillus made of tiny hematite flakes might grow (as I have mentioned in many previous posts - roll 'em up like a snowball). If the spherules hadn't grown this way, they wouldn't be shiny or specular on the outside. What Glotch et al. fail to discuss is why a sedimentary concretion would consist of shiny blue-gray hematite (the specular form) in the first place. They claim to have grown some hematite at high temperatures by some unspecified process - but it wasn't a hydrothermal brine or salty steam, as far as I know. I think they probably just dry roasted red hematite. In this case as in many others (including part "A" of that figure), they picked their own straw horse to shoot at - they're certainly not shooting at us or at anything we ever claimed as a possibility. That part is not particularly great science, IMHO.

BTW, very enterprising of you to look that reference up. My compliments. It just doesn't prove what you thought. It only explains why the spherules are shiny (they contain shiny flakes that are facing outwards), which anyone with the least understanding of crystallography already knew. It does NOT explain why they are blue-gray, as far as I can tell, and it certainly doesn't disprove anything we've ever claimed.

--HDP Don

...sounded pretty convincing to me!

However, why couldn't a less catastophic 'unimodal' process repeat itself many times (i.e., short-duration groundwater flooding events) and produce similar results? If other influences such as wind erosion (presumably minimal by our standards over medium time frames) and precipitation (utterly absent) are nullified, wouldn't this tend to generate much more uniform berry distribution if for no other reason than that the process is much simpler than its terrestrial analogs?

MarsIsImportant - These are pretty obvious, and I've already stated them many times. If Oppy were to find actual lake beds, that would provide positive evidence for the vanished lake hypothesis. If it found large, non-spherical berries, or multiply clumped berries, or berries related to fluid passageways, that would provide positive evidence for the concretion hypothesis (the shiny, blue-gray nature would still be totally unexplained, as would the elevated Ni content). If it found huge salt crystals, or their casts or imprints, such as typically grow beneath the surface in playas (or anywhere else that salts are soaked in brines) that would provide positive evidence for the soaked-in-a-brine hypothesis. If it found actual mud (especially mud containing mud cracks), that might provide positive evidence for the interdune playa at a water table hypothesis. If it found braided stream channels, or other types of independent evidence of flowing water, that would provide positive evidence of the highly ambiguous (IMHO, completely non-existent) "festoon problem" (just look at them "festoons" in the middle of the cliff at Cape St. Mary - my post #79). And so on.

I cannot emphasize this enough - there is NO POSITIVE EVIDENCE for the hypotheses that provide the individual parts to the highly complex extant model, other than the salts (wrong mix and wrong grain size for evaporites - so they had to get the wind to bring them from somewhere else, vanished), cross-beds (ambiguous - but certainly not typical dunes, for the most part), and spherules (millions fail any reasonable statistical test for concretions; the concretion hypothesis cannot explain their Ni content or shiny blue-gray nature).

There already is POSITIVE evidence (based on Oppy observations) for EVERYTHING in the extremely simple impact surge hypothesis (salt mix, all bedding features, shrinkage cracks, spherules and their nature and distribution, impact craters everywhere, related deposits seen from orbit, nearly identical features seen at Home Plate, the whole shebang). You couldn't ask Mars to produce anything more. The lack of coarse material (to quote you, absence of evidence is not evidence of absence) is easily accounted for by making the impact target distant or allowing it to be Meridiani-like itself (beat up on Meridiani and you'll get more Meridiani, as predicted by William K. Hartmann in his "kablooey of dust and steam" phrase). The lack of abundant Fe-sulfides (again, absence of evidence is not evidence of absence) seems not a problem - how else than by destroying them are you going to form jarosite or other acid sulfates? (Although acid steam in the surge cloud works too.) The abundance of specular blue-gray hematite in the accretionary spherules is not unexpected for a salty, steamy surge cloud on such an exceedingly iron-rich planet, although I'd predict that other compositional varieties of spherules will also be found. Keep in mind that if there hadn't been something unusual about the Meridiani spherules, Oppy would never have landed there.

The main problem people seem to have (especially you) is they apparently cannot believe that Mars would throw Oppy and its team a fast one - would not meet everyone's prior desires and expectations (i.e., would hand it a two-headed coin to flip, as per my previous post to you). Well get used to it. Begin to suspect. Mars loves to play tricks on our expectations. It's not what we want it to be, it's what it is. It is an alien little planet, after all. That's all for tonight. (And I'd really rather make the debate a little less repetitive tomorrow, else I may have to give another quiz. Or would you prefer a classroom demonstration? )

--HDP Don