Those of us who are interested in exploring alternatives to the "cold, dry Mars hypothesis" and its associated basal surge mechanism (to account for Meridiani's layering) are in essence being subjected to denial of service attacks -- the available bandwidth is flooded with large, somewhat repetitive posts from the cold, dry Mars camp, though the intention is clearly educational and not malicious!

As a practical solution, I am therefore starting this new thread devoted to the basal surge theory, with the hope that discussions of such can be centered here. And, even though I do not believe in basal surge, I am going to present my own layman's analogy -- probably not original -- as an attempt to justify the theory, which analogy has two additional purposes, a) as a gesture of goodwill, and as a new way of looking at the mechanism which can hopefully prevent us from entering an infinite loop.

To me (and many others), the Meridiani layering is so uniform that it must clearly be the result of a seasonal/water-based process -- not basal surge.

So -- how could one possibly reconcile the layering uniformity with an origin of catastrophic meteor strikes?

Imagine, therefore, a series of balloons of varying sizes and each filled with a different colored paint. Imagine also that these are dropped sequentially -- but with time for the paint from each impact to dry -- at random but adjacent locations on a level surface such that the splash patterns tend to overlap.

Under this scenario, it must be granted that a cross section through the dried layers of paint might show that the layering was reasonably uniform, ie, the paint from each impact, even though its source is a "catastrophic", spreads out in a thin, uniform layer -- just as one might imagine that the pyroclastic outflow from a meteor strike might also create a uniform layer.

Anybody want to throw a dart at this -- and leave the other dart boards alone?!?

Impact ejecta is not paint. Once it settles it is solid material. It is significantly thicker the closer it is to the crater.

I really like the color idea. It helps me visualize the 'beautiful messiness' a series of impacts and the resulting surge clouds would make in the 3-D layer structure.
(I imagine Jackson Pollock flinging rocks from space down to the surface)

To address Shaka's point, maybe a better analogy would be some sort of colored material capable of gradiating outwards.
Like maybe colored aquarium gravel, same-colored sand, and same-colored flour aerosolized in the same balloon.

And each time the stuff settles out, the next impact will excavate and fling outwards some of the newly laid down sediments also (but probably with chemical modification?).

Very pretty. Thanks for the concept!

Interesting start to a discussion, but keep in mind that Mars, unlike the Moon, has an atmosphere, so that impact-generated fine material will necessarily be "flung out" as a turbulent mix in a rapidly travelling density current or cloud. Grains (and pretty colors) will inevitably be mixed (result = ugly brown) and, yes, chemical modification (and grain cementation) will probably occur, in part owing to moisture condensing on sticky salts in the cloud. Also, material should become segregated by grain size as the cloud loses energy. Finally, an impact into fine material (such as that pulverized by previous impacts) can kick up (rework) only fine material (pointed out by Bill Hartmann). These sorts of processes can occur at any scale, from dozens of meters to planet-covering. Sorry if this is too technical - feel free to ignore it.

-- HDP

If you take liberties with the accuracy, a simulation would make just an *awesome* screensaver.

Random impact locations, with random impactors sizes carving out proportional depth craters and colored sediments (no mixing, no transformation to brown, just a spread of pretty color of the deepest layer across the tableau) would be very pretty.

(And accurate to a degree for an airless surface with ballistic ejecta trajectories, but not for a turbulent surge cloud)

Far from "too technical", this is wonderfully lucid summary and should not be ignored. But how does it relate to Meridiani Plain?
Please, Don, can you show us any photographs - from Oppy's Meridiani journey - which demonstrate these processes? I haven't seen them so far.
Instead of "turbulent mix", "grain cementation, ...condensing on sticky salts in the cloud", "segregated by grain size", "kick up (rework) only fine material", "at any scale", I see only the repetitive (yes, boring!) invariant laminations - hundreds of the bloody things - left behind by the passage of endless sequences of sandy dunes - well-sorted, un-turbulent, devoid of "sticky" agglomerations or aberrant inclusions of shattered ejecta, of tediously predictable scale.
Why am I missing all the fun?

Yeah. More like primer, undercoat and lots of topcoats all thinly applied by brush. Paint balloons or impact surge is much more fun - damn that pesky evidence.

Umm, perhaps because you haven't been paying sufficient attention? Have you ever looked closely at, e.g., Home Plate in Gusev Crater, believed to have formed in exactly that way, with exactly the same boring, sometimes dune-like bedding (and with even an underlying hematitic bed rich in tiny spherules)? Not wishing to beat an utterly dead (and mostly unloved here) horse any further, I suggest you re-examine the far-too-lengthy, two-year-old thread on exactly this topic further down under Mars (General): http://www.unmannedspaceflight.com/index.php?showtopic=4308.

Juramike, at a planet-wide or regional scale, individual surge deposits could probably be "painted" as a single color, resulting in a very pretty map covered with overlapping colored circles of various sizes. One problem is that you would very rapidly run out of distinguishable colors (too many impacts!). Another is that the distal deposits were probably heavily eroded by the wind and were perhaps rather thin (only a few cm) to begin with, so it would be difficult to know how many crater diameters to draw them (10-20 might be conservative). As a possible example, I've suggested that at least two different thin surge deposits are exposed in the cliff walls of Cape Verde in Victora Crater, where an unconformity (technical term for an old erosion surface) is clearly exposed (see, e.g., pictures and discussion in the May 22 issue of Science, p. 1058-1061).

-- HDP Don

You seem to be fairly new here; if so, welcome, but I strongly suggest that you read the lengthy 2-year-old thread cited just above. Although not all questions can be answered unequivocally, there's so much visual evidence for impacts and, by implication, for impact surge deposits, and so little evidence against, in exposures at both Home Plate and Meridiani Planum, that I find it fairly embarrassing (but then I've probably become a true believer over the past 5 years).

When it comes to visual evidence, consider the following: If my trusting wife were to come home unexpectedly and find me in bed with our beautiful neighbor, what evidence should she believe, that of her lying eyes, or the erudite, complex, overly technical explanation that I could perhaps provide her with at my leisure, based on her prior expectations (i.e., Rosenthal effect)? BTW, my wife did just this minute come home from watching a Phoenix Mercury preseason game and found me innocently sitting here at the keyboard. Time to pay some attention to her, I guess. Good night.

-- HDP Don

This topic has been discussed - to the tune of seveal tens of thousands of words contribution from Don - here - http://www.unmannedspaceflight.com/index.p...0&start=320

My words in the last post of that thread stand. Please read them.

Can someone describe an experiment that would stand a good chance of settling the question? I'll admit I I only read the first quarter of that long 2-year-old thread, but it seems that if the argument has reached a stalemate based on current data, it would be interesting to know what sort of data some future probe could collect that would resolve it.

Also, can someone give a crisp statement of the question? Is it as simple as this? "The MER Team argues that the Meridiani geology has water-formed features, but Dr. Burt claims all those features are the product of impacts."

Apologies if this has already been gone over in detail. Just post the link. :-)

--Greg

Greg, substitute the word "layering" for "geology", and eliminate the word "all", and I think your summary statement is about right.

Juramike, a screen saver would be cool! I wish I could clone myself about a thousand times, and one of those clones would be put to work figuring out how to do it! You are obviously pretty darn good with computer graphics, so be my guest!

And Doug, Juramike's idea of a screen saver makes me realize even more the potency of a visual approach to the layering question, and its potential for preventing this topic from entering an infinite loop yet again; hence, I present this image:


Click to view attachment

This is, of course, Tycho Crater. In contradiction to my own paint balloon analogy (which is in itself a straw man), it's hard to see how you'd get Meridiani-type layering from this -- albeit Tycho is more of a high speed paint ball (versus balloon) impact on an airless world. But informative nonetheless.

Oh, and this is really rich: this image was found on a crackpot web site that apparently seeks to explain natural phenomenon in terms of thunderbolts, with Tycho being the result of an electrostatic discharge between the moon and an approaching body. I kid you not!!!!!

Question: Blueberry - hailstone or concretion?

Experiment: Close study of a blueberrry.

At least one thing that has sunk into my brain is that even the thin atmosphere of Mars makes all the difference.

Other pairs of cents on the subject:
~I personally find the basal surge hypothesis compelling, even if it turns out to be wrong in the case of Meridiani and/or Gusev. I think it is useful to put at least a little pressure on the prevailing hypothesis to continue to prove itself against at least one competitor and I don't think the case should be closed so easily. There's no reason it has to be an acrimonious debate, just intellectually stimulating.

~When dburt finally get's his Basal Surge website up and going, the aforementioned "too long" thread would make a great basis for the "Frequently Asked Questions" section.

...or Frequently Answered Questions.

Seriously though, continuing this debate does increase the risk that Glenn might be seduced by "crackpot web sites", or Don by his "beautiful neighbor".

I don't know, it may be keeping Don out of trouble. His wife did find him at his computer. If not for the lure of the debate....

Unless you're pulling my leg, I don't see how that works. Unless you're including meteoritic infall as "hail" . . .

But if you are serious, please explain; this is very compact indeed! :-)

--Greg

Boy, are we having fun!

Seriously, though, and in the spirit of Centsworth's belief that we should give the basal surge theory the benefit of the doubt, I would like to expand on ngunn's mention of hailstones.

The blueberries, to me, are clearly concretions, and not projectiles or ejecta. (I live not far from a part of Louisiana [Washington Parish] where hematitic concretions in the soil are common, and, except for the color, they are very like the blueberries.)

However, hailstones -- which also resemble the blueberries -- are a kind of atmospheric concretion, and perhaps one could argue that blueberries coalesce in the cloud created by a meteor strike and are scattered as part of the deposition of the freshly created layer.



Again, this seems rather far fetched to me, and I mention it only by way of going the extra mile to accomodate Dr. Burt. Not to mention the following related points, on which I would be grateful for some corroboration:

1) Does not the formation of hailstones require a strong updraft, to hold the hailstones aloft, or at least slow their descent, as they form layer by layer? And how could equivalent conditions obtain after a meteor strike? In the strong updraft from the explosion? Or in the parabolic arc of the ejected material, in which there would be a kind of equivalent weightlessness? And how do either of these scenarios square with the idea of basal surge, which, I assume, means "ground hugging"?

2) Did not a RAT cross section through several blueberry-filled layers specifically show that the layers under the blueberries were NOT dimpled as if from impact?

Doug, sorry if I am covering old ground, but I am doing so only in response to new comments that have been made here, and, I hope, in a way that sheds new light on things . . .

Sorry, but yes, you are covering old ground, so far (and no one would know better than me). New ground would be most welcome. Feel free to PM me if anything particularly bothers you. And Centsworth and Shaka, most of my female neighbors were probably beautiful at least 50 or 60 years ago..., but I do appreciate UMSF watching out for my virtue.

-- HDP Don

Please don't. Doug was serious. Discussion closed.