John

As a result of Irishman's and Phantomwolf's discussions, I have some areas I will address with supporting detail later.

In regard to your questions 1 through 3, they have already been addressed specificially by me. You reiterating the questions serves no point if you ignore my answers.

Citing this forum as evidence of what is the truth is an appeal to popular opinion and not how any scientist I know conducts his research nor provides evidence for his argument. Furthermore, given BA's articles on Hoagland it would seem obvious that this is a haven where those who support BA's views would gather. That is why I am here, in hopes of a hostile, challenging audience. I could just as easily argue that there are those who do not see the convexivity disappear when the image is rotated 180 degrees, as is advocated by BA, which I noticed in several posts here upon my arrival and yet saw none having any epiphany when the image was rotated. Yet such arguments are irrelevant to the resolve of the features. However suffice to say, virtually everyone in this post has seemed to have no problem recognizing what is being referred to by the "convex" claims except yourself.

Jon, I have been interpreting aerial imagery since age 14 as a result of my scuba diving and interest in oceanography leading me to work with FIT studying erosional concerns resulting from ACOE groin fields and their effect on coastal barrier reefs. I have been looking at satellite imagery for some 20 years and been contracted almost equally by private industry and the US miltary for interpretation of that imagery and other remote survey methodologies. I am more than proficient with 3D interpretation of imagery, recognizing geomorphologies and interpreting morphogenesis. Why dont you try some other avenue.

Yes, I can do so, but why would i want to provide you further credentials to cite beyond your own and other's arguments to present to facilitate you not doing your own research and not addressing existing arguments such as the deviation of these 'dune' features from aeolian mechanics on "geomorphic grounds"? Furthermore, these "evidences" are not on public display because, as I've indicated, JPL chose to release these statements in a non-public fashion and JPL/MSSS/NASA have not addressed these features in any public manner, yet showed an ongoing interest by reimaging the exact same piece of Martian terrain. Despite the lack of public discemination by JPL, there is every liklihood you would find the JPL references on your own if you were to exhert even a minimal of effort.

Once again you have read me incorrectly and fail to address the real, specific concerns entirely.

What i said, essentially, was that an equally INVALID anaglyph could be made to show convexivity.

Simply making an anaglyph image that shows a 3D impression does not make it "valid".

Jon, the fact is that the horizontal relative displacement or "error" between the two images due to imaging angle far exceeds even the widths of the valleys themselves, making it impossible to interpret the vertical relief of the much lesser 'dune'features, where that relief is representated in a far smaller horizontal displacement aspect of a lesser vertical relief than the valleys themselves.

As I have stated, one might map the two images to make them correspond better but such a methematical correlation fails to recognize the horizontal offset from verticle relief and treats all terrain detail as if it were horizontal, which it obviously is not, Even the verticle relief of the valley walls themselves would be treated as if horizontal detail in mapping, thereby creating distortions and further removing these two images as objective representations of the 3D terrain in pristine form.

The non-mapped image comparison below clearly demonstrates that there is no way to correlate the the two images into an 3D anaglyph composite as they exist



So, Jon, specifically by what means do you maintain it is reasonable to correlate these two divergent images to make a 3D anaglyph?



Regarding: M15-01228 and M01-03437:
By 'articulated' i am referring to the these high albedo features having such startling definition or relief. These features in both images are notable due to the high positive relief of these features and the minimal distance between them. I was not referring to them 'bifurcating" which I do not see any profound evidence of in either image. While your dune images are a nice survey of Dunes on Mars, none of the images begins to replicate the detail seen in M15-01228 and M01-03437.

Regarding "Fetch" involved in dune mechanics, specifically interdune mechanics:

"Dynamics of secondary airflow and sediment transport over and in the lee of transverse dunes"
Ian J. Walker and William G. Nickling

Startling definition and relief?? These are two low quality images, they show no clear sharp features. If Tripp is such the ariel photo expert as he states then he should have no problem finding Kyle MacLachlan riding the giant tube worms out in west texas and white sands new mexico via several online satilite mapping services. Or try google image search on sand dunes/dessert photography and behold, nice single file lines of sand dunes everywhere, or perhaps they migrated from mars to earth.

Perhaps the dreaded phrase to woo woos: Occam's Razor would cause some peoples heads to explode.

__________________
-- the only conspiracy I believe in is this damn monopoly on breathing air.

I would sincerely besurprised if your grasp of Sir Occam exceeded your lipservice to him just as your other scattered irrelevent references. Incidentally, I make no reference to these features as being biological in origin nor have I used "worm" anywhere. Woo woo that. Have you got any valid contribution?

In fairness, M15-01228 actually has higher resolution available. The best resolution (uncompressed) .gif image of the same locale (downloadable from the MSSS website: http://www.msss.com/moc_gallery/m13_...5/M1501228.gif -- WARNING: It's 3.1 Megs) in the image is about 50% larger (roughly 465 vs. 315 pixels across for the .jpg in the link. This additional resolution, however, does not support Tripp's assertions. On the contrary, IMO.

In addition, scanning southward in the same strip (within M15-01228) are a number of in-valley dune-trains with varied morphologies. It would take some creative license to see all of them as convex landforms.

__________________
“The simplest schoolboy is now familiar with truths for which Archimedes would have sacrificed his life.” – Earnest Renan

Well acid trip... Most of what you present is not substatiated in the photographs besides your opinion of the artificality of these structures as you ramble on in your postings.

I case you need a remider tripp here you go http://en.wikipedia.org/wiki/Occam's_Razor
At least that way you can rebut a foundation of some knowledge.

Of course seeing as how your sense of humor about the "worms" per say has been lost like the Beagle 2. =D>

eye-zee thanks for the link to the high res shots, show lots of pretty marching dunes.

I think instead of grasping at the artifical aspect of them, perhaps the more compelling and scolastic approach would be to understand the unique weather and topographical features that make these. Could go along way in helping understand the desert encroachment on fertile crop lands that poses farmers a major headache in trying to feed the world.

On the other hand on the remote chance they are a "worm" that would be alot of meat if we could harvest them and ranch them here on earth. Miles and miles of worm steak, yummy.

__________________
-- the only conspiracy I believe in is this damn monopoly on breathing air.

jawajedi, I suggest you go read the FAQ:
Your behavior with Tripp (such as calling him "acid trip") is crossing that line. Don't get yourself banned. Behave.

I'm all for a good joke, but calling names is just rude, and accusing him of holding beliefs he doesn't is a straw man. You're not helping!.

Though the idea of ranching giant Dune worms for meat.... Hmmm.

I made no mention of artificiality. I have been arguing these features within natural geomorphic parameters only.

I am well acquainted with Occam. Your delivery of nothing but your verdict serves no one and does not advance the discussion in any direction unless you misinterpret Occam to be a popularity poll.

Irishman, Thanks.

Tripp

Regarding your post on Thu Apr 08, 2004 7:46 pm. When did you answer my questions?

Q2 If these features are not dunes, how about you come up with testable alternatives?

Prior to my asking this question (Thu Apr 01, 2004 10:45 pm and Mon Apr 05, 2004 10:22 am) you suggested they could be lava or glacial flow features (Thu Mar 25, 2004 8:25 am). As I pointed out subsequently (Sat Mar 27, 2004 11:25 am) scale is wrong for the first, and the geometry and associated landforms are wrong for the second. You did not respond as far as I can see. The only testable suggestion I can find since I asked these questions is the glass tube (Mon Apr 05, 2004 8:50 pm). You tender no evidence for this so I do not take this seriously. If you have come up with more specific alternatives, I must have missed them. Why not repeat them for everyone’s benefit?

Q2 What evidence would you accept as indicating the transverse features were dunes?

I cannot see where you have addressed this question. If you have, once again, please repeat them.

You wrote: “virtually everyone in this post has seemed to have no problem recognizing what is being referred to by the "convex" claims except yourself.” Wrong. Just about everyone in this conversation does not see your convex illusions. Not only our noble host, but Aurora, beskeptical, ToSeek, PhantomWolf, 01101001, Irishman, and jawajedi (though I too find the aggressive manner distasteful).

Your refusal to answer question 4) suggests strongly that you don’t have the evidence, and that the alleged JPL correspondence is as fictitous as the alleged reference to these features in the press release about Vallis Marineris.

Your refusal to provide an anaglyph that shows convexity in this area suggests that you cannot.

The transverse features in the Acidalia valleys show all the characters of the dunes in the other images: consistent orientation, confined to valleys, tuning fork terminations, ends broken up into shorter wavelength features, smaller sets oblique to and superimposed on the main dunes, and variable wavelengths. So, another question:

Q5) Why do you accept the features in the other images as dunes and not these? Or, to put it another way, list the features in the Acidalia valleys not consistent with them being dunes.

Thanks for the Nickling and Walker reference, I would have appreciated more if you had provided the link and citation. For the benefit of others, it can be found at http://office.geog.uvic.ca/blast/Pub...IPG26-1p47.pdf . It is important to read the quote (from the bottom of age (70) in context. It reads: “For instance, over closely spaced dunes shear stress progresses toward a maximum at the crest of the downwind dune with a value that is proportional to the boundary layer development distance, or effective fetch, beyond re-attachment.” The following sentence reads: “However, because wake effects and flow perturbations (e.g., pressure stagnation, surface flow amplification) impede boundary layer development, boundary layer recovery may never occur over closely spaced dunes, especially during fully turbulent, transporting flow conditions.” In other words
Yes, fetch a factor in dune development, but the distance is small, typically less than the wavelength of closely spaced transverse dues, such as these. My original contention that fetch is not important as an issue in due localization compared to sand supply (Sun Mar 28, 2004 5:09 am) still stands

So I suggest you actually engage the real issue as to the nature of these features, summarized by questions 2, 3 and 5. If you do not then there is not much point continuing the discussion, is there? I am quite happy for these features not to be dunes, if the evidence is forthcoming. Are you likewise prepared to change your opinion on the nature of these features ?

Jon

Jon, I answered your questions HERE quite directly, even citing your specific questions verbatim as quotations.

This request of me is patently ridiculous as no alternative is reasonably 'testable" on Mars at least not with more data than is now available. Furthermore this excahgne with you has had conspicuous difficulty evne establishing what is "convex" not to mention recognizing inconguencies in the "dune' supposition. Beyond these, I addressed this question at the above url.


No. I did not in any way suggest these were lava or glacial features. I only suggested similar arcs also appear in lava and glacial features. I have no belief these forms were originating from these morphogenic processes. Your objecting to these as lava and glacial features came as no surpprise to me and i glossed over your words without reading them because they did not provide me any new info and you had evidently missed my point or were speaking for other's benefit.

I never said these were "glass tubes" and your misrepresentation of my words is long past being a barrier in our communications. We have been dealing with the difficulty of your recognizing the convex form and then your failure to respond to how these features do not adhere to aeolian mechanics.

I already addressed these. Again reference my first cited URL in this post.

NO, Jon. I am not wrong. My statement was that everyone but you seemed to have no problem recognizing what was claimed to be convex. You showed your inability to recognize what was being disucussed repeatedly. No one else,.even those who disagree that it is actually convex, has any problem recognize the convex appearance. THey see the convex 'illusions" and want to dismiss then as an illusion. (There can be no illusion if something is not oevertly and commonly recognized to be other than what it is) I have no basis for intelligent exchange with you given your deficit in this matter and the barrier in discussing fundamental concepts.

Jon, are you calling me a liar? There is zero doubt whatsoever that these individuals are referencing this specific terrain. My refusal to provide the reference does not need to be intuited nor interpreted at all; I have stated my reason quite explicitly: their brief email addresses of these features have no bearing on a directed dicussion of those details other than providing you a lazy reference. I have even cited these persons words describing these features in this thread to better express what is in evidence.

I can make an anaglyph.

I can make an anaglyph of those two images.

I cannot make a valid anaglyph that shows anything reliably representative of the terrain from those two images.

Everyone else in this conversation seems to have entirely dropped any and all reference to the anaglyph as demonstrating any truth of this image. I suggest there is a reason for this. What do you suppose that reason might be? If you have trouble resolving this on your own try rereading my previous posts which you do conspicuously fail to address.

Constructing an invalid representation of these convex areas (which you quite clearly are unable to identify) entails only suitably offsetting these features in composite layering, as you yourself recognized is 'appropriate' and doing so without regard to other features. In knowing what one is doing one even has the option of making them appear to extend into the screen or project outwards. All of this is a waste of my time, which I have no intention of engaging in, especially with the only product of this effort being to teach you that these two images are not even close to reasonable candidates for a 3D anaglyph image.


Jon, are you so unable to recognize that the anaglyph is invalid that you must fabricate an irrelevant test for me to create yet another invalid anaglyph rather than respond to this fact?

Because the other features concur with common aeolian mechanics and these do not. The 'characteristics" you list of these complying with aeolian mechenics are actually suppositions you maintain to comply with your prejudicial pre-existing evaluation of dunes, suitably ignoring my challenges to how this violate aeolian mechanics.

No, nowhere in that extended citation does it indicate that fetch is irrelevant when smaller than the wavelength. That is your prejudicial interpretation which is nowhere indicated by the text. What that passage indicates is that boundary layer may never reform in the turbulence and, implicitly, so too is the wavelength no longer maintained in that turbulence. Reasonably, the wavelength is no longer responsible for periodicity in such tightly spaced dune distribution where lee calm is the primary factor in grain deposition in absence of turbulence.

The simple reason "fetch" is not more often directly addressed in dune study is that it is implicit that the fetch is sufficient if winds have already formed dunes. The fact is that winds on Mars have far less force to lift grains amd initiate saltation due to atmospheric thinness and fetch becomes a greater factor in determining where dune formations may and do appear.


Jon, I suggest you do a better job of following the exchanges. not ignoring what is convenient and incorrectly rephrasing what suits you because at this point your continually hoisting your ego from the highest yardarm has seriously derailed all coherent exchange on this matter.

I didn't see it mentioned so in case you haven't read it, it is nicely done.

here

Even the puns are high caliber, such as..."Pane in the Glass".

__________________
Lighten up! This is a stellar board!

JonClarke said:
This is a misstatement, or confused wording. Most of the folks listed do see the convex shape, we just realize it is an illusion and can see through it as well. You apparently cannot see the convex shape at all, and Tripp apparently cannot see through it. Or prefers the convex shape interpretation.

Tripp, thanks for the link back to your previous address of the questions. I checked, but some of the responses were not satisfying - they feel incomplete.

Is this perhaps explaining that you did not connect his question with the valleys we have been discussing? If so, okay, but it seems odd you wouldn't make that connection. :shrug:


So your response is "unknown combination of morphegenic mechanisms". Well, that certainly is difficult to test. It would be easier if you could more clearly state exactly what it is you think you are seeing. I have been trying to interpret your posts to understand, but can't find a clear explanation. You don't agree with the glass worms, but are you thinking glass tubes? You don't think it is artificial, but rather some natural geomorphic feature. What? You dispute that it is lava tubes, so what are you proposing it is? You have connected the "tubes" to several craters you state are vents - what kind of vents? How are the tubes related? What is the material of the tubes? Not lava, not glass, what? Again, if you would explicitly state a hypothesis then we could talk about that specific. Without you declaring your position, we are left with
a) it is sand dunes in valleys;
b) it is something else, unspecified.

Not much to work with there.

I'm sorry, but there is substantial doubt that the individuals are referencing these features. JonClarke has provided a link to the comments as they were made, with pictures of the features being addressed by those comments. They did not specifically reference this region of Mars, and did specifically address other regions. They showed a number of example pictures, none of them from this region or resembling this region. The pictures shown had a very different characteristic look, and those images are hard to interpret and do not look like dunes. These features do look like dunes. So you are mistaken to connect the statements made by the scientists about non-dune features with these features.

So if you have some other evidence to suggest the scientists meant these specific features (such as emails), you should provide them to back up your assertion. Otherwise, the case is pretty clear you are in error. Your motivation not to provide them is not something I wish to speculate on, but the evidence as it stands is counter to your claim.

Here's the point. JonClarke feels the anaglyph is representative and accurate. You claim it is not and that an equally invalid anaglyph can be constructed that makes the convexity more apparent. If you provide the invalid anaglyph that shows the convexity, you will prove that the anaglyph is in question. But you do not, you just claim it is possible to do so. And I'm supposed to take your word for it? It doesn't matter if the anaglyph accurately represents anything or not - the point is that the current one is inaccurate, so show another inaccurate anaglyph with a different outcome to show the current one is questionable.

I don't have the glasses to view it, and am not versed in the technical aspects of how to make one. Thus I have avoided the topic. That does not mean it is not a valid topic, just that I don't feel I can provide adequate critical evaluation either way.

But that is exactly why you should do it! Prove the two images are not good candidates for a good 3-D image. That's not a waste of time, that's demonstrating your point, not only to him but to me and others as well.

I don't know about Jon, but I sure could use a demo.

In using "these features", Jon is referring to the high albedo arcs of the "dunes" and, in my view, limiting the perspective of the discussion to those features alone and thereby curtailing the discussion and obserations, which suits his case fine, but not an honest address of the details.

Meanwhile, Irishman, your questioning my seeming reluctance to connect Jon's question with the valleys (which Jon himself did not do, and I believe intentionally) also muddies the waters because the outward concave nature of the large valleys themselves is more than apparent and not in question, but this has nothing to do with issues being debated.


Isnt a conclusion premature when the discussion of what is in evidence is not resolved? How do you reasonably "test" a conclusion, such as "dunes", when the depth of the 'test" is the same as that which resolved the conclusion? (rhetorical)

I have stated what the evidences were and addressed contradictuions with the "dune" conclusion as well. If BA's article is being praised and these details are in question, then what is being considered in praising that article?


I have only been discussing the evidences. However there is a good chance the equiangular orientation of the tri-radiate valleys is not happenstance, which I have expressed before in this thread.



Actually you are mistaken and the reason you are mistaken is your confusion over the subject matter of the exchange between JonClarke and myself.

JonClarke was referring to my reference to JPL scientists' emails discussing the visual appearance of convexivity in the very area we are here discussing, which is what i was addressing in my response, and NOT the 6th paragraph of the JPL Media Relations Office detail from a live press conference held on May 22.2000. The emails to which I refer,were not ever officially made public by JPL and were. again, quite undeniably referencing this specific image and these debated details.

The features you, Irishman, are referencing, are described by Edgett and Malin as " Ridged layered geologic units (they're not dunes)" was released in March 2000 at the "31st Lunar and Planetary Science Conference". This material is hardly worthy of mention of all the conference reports two months later at the May 22, 2000 JPL Public Relations Office announcement of the Mars satellite imagery availability on the web at http://www.msss.com. (Incidentally, I watched this entirety of this press conference in its live broadcast)

The case is only "pretty clear" to you because you are predisposed to your answer.


You dont have to take my word for anything.

The visual appearance of convexivity in an anaglyph image is the result of features being offset (ideally from vertical displacement) in two images taken at slightly varied angles (intended to approximate the offset of human eyes). Any offset of features by the appropriate amount would create such a forced perspective in an anaglyph image. Anagyph imagery is reasonably held forth as evidence of relief and a recreation of what is recorded in the imagery when the two images are taken at nearly the same positions.



It should be clear clearly obvious that the two images. Above, are so widely divergent (30+ degrees as opposed to 2 degrees) that no correlation of features that exist across the image can be maintained in both X and Y coordinate directions. You might deliberately correlate features to allow a 3D appearance for a short distance (and this is what Jon is seeing) but not continually across the image and with no objective, reasonable means to assure these are real representations. Even the *OBVIOUS* and clearly deep, convex shape of the overall valleys themselves cannot be maintained in the anaglyph (unless it is done with mapped images, and such mapping distortion of the original imagery aspects immediately invalidates the anagyph result as no longer representative of the direct imaging) ,

"Here's the point. JonClarke feels the anaglyph is representative and accurate. "

No, actually JonClarke maintains the anaglyph is representative only and does so because it shows *ANYTHING* at all with a 3D relief. Jonclarke wrote "You ask how I can maintain the analgyph is valid. My criteria for it is simple: it works. With it I can see in stereo. " JonClarke is not all concerned whether this anaglyph is "accurate" but is more than happy to reference it as 'proof" when it serves his case (which is no surprise given the creator).

The "critical evaluation" here has nothing to do with owning 3D glasses to view the imagery. (If you want a pair which is easily obtainable simply go to your local Blockbuster video store and ask if the "Spy Kids:3D" video glasses might be given you free of charge) The "criticial evaluation" here is, as is so often the case, in the evaluation of the validity of the original data. A simple comparision (evident in the above image) of images shows these are not reasonably candidates for creation of a 3D anaglyph as there is no means to correlate them and maintain the image perspective that is the reason for creating the anaglyph in the first place. THis is a case of "garbage in, garbage out". While these individual images have value on their own, they have no value whatsoever as a stereo-optic pair. Even the lighting angle variances ALONE are enough to rule out the appraisal of features the size of the slip and windward faces of the "dunes" in an anaglyph image.

And that is exactly what I have already PROVEN in the above image comparison! Creating a whole other anaglyph with 3D aspect to the 'tube' features is irrelevant to any "proof" and a supreme waste of time. When I create an anaglyph I remove appropriate red or green/blue channels in either image and then composite the images to finish the 3D anaglyph. I myself use photoshop. Creating such a false anaglyph would take several trials and errors to create an ideal image correlation. While there are software programs that do all the interim steps. I don't own such a program and dont need one because valid anaglyphs are straighforward and dont require fudging to create. My teaching how this 3D perspective is achieved and creating one single anaglyph is hardly reason to purchase such a program for a one-time use.

What you are really asking for is a demonstration of how 3D anaglyphs work and not any sort of "proof" of why these two images are not candidates for a realistic 3D anaglyph composite, which has already been provided. The only way these two images would be worse candidates would be if the original image angle was offset at an agle opposite to the second imaging angle. What you're really requesting, an understanding of how 3D anaglyph perspective is achieved, can be obtained from a search of "anaglyph" over the internet.

I see, the limiting of the focus to the ridges rather than the valleys as a whole.

This is what I mean. "A good chance the equiangular orientation of the tri-radiate valleys is not happenstance." What does that mean? What would/could cause it to not be happenstance? You throw out tidbits and hints but then don't explain what you mean.

You mention "vents" but then don't describe what is being vented or how they are connected to the convex tubes you say are there. But when asked details (like are they lava forms) you deny the specifics.


Thank you for explaining the confusion. Of course, it's a little unfair to make reference to emails that we can't check and use that as a basis for your statements. JonClarke did find a very similar statement in a public release, so it is not irrelevant to show that statement and what was addressed by it. You have not provided any evidence of another statement that is similar but addressing the tri-radiate valleys. How can I evaluate that? The most I can give you is that maybe the scientists are wondering about these valleys. But given how they've presented publicly questions about other features that they are puzzled over, that leaves that speculation a bit unfounded.

I'm willing to evaluate evidence, but how can I when I can't view it (the emails)?


Actually, I located a pair. And I agree. I was making two comments. 1) no glasses, and 2) lack of knowledge.

Okay, I here what you're saying. I looked at the image and it seems to work for me. My work has posted a bunch of these around (not this feature in question, though), and it works as well as most of those. :shrug:

I will try to look more into anaglyphs to further my understanding.

Tripp

I wrote a longish post yesterdaybut it seems to have been eated by the cyberspace ghoul So here goes again.

Your response to Q2

A request for testable alternatives to the dune hypothesis is standard scientific practice. The dune explanation makes a wide range of testable predictions, alternatives should do likewise. If you don't produce testable alternatives them you are not working the problem scientifically. The only apparent alternatives to dunes I can find you mentioning were lava, ice, and the glass tube. If this was not you intention, my apologies. So please quote what you genuine alternatives, rather than a generic link, it would simplify matters.

Your response to Q3 (which I had incorrectly typed as Q2)

Thank you, I have found your reference to MOLA in the link. In the absence of MOLA data and your rejection of the analgyph, what other data that is to hand would you accept?

Your response to question Q4

Only you know whether or not you are a liar. However refering to vague unnamed sources then not providing them when asked if not good scholarship.

With respect to the analgyph

If you were to produce an analgyph from a different combination of these images that produced apparent convexity it would greatly strengthen you argument that the concavity is also illusionary. If you are able to do with I would encourage you to do so.

Your response to Q5

Rather than general statements about how these features do not comply with aeolian mechanics, please list the specifics. Rather than dismissing as prejudical suppositions without explanation my list of ways in which these features resemble other dunes, please show how they do not.

With respect to aeolian fetch

There seems to be some kind of semantic confusion going on between us. Let me reiterate: fetch is a term rarely used in connection with sand dunes. A searcg through GEOREF (the premier geoscience data base) showed only a handful of associations of fetch with terms such as aeolian, eolian, dune, etc. In those references it is used in at least three different ways: the distance needed to reestablish the boundary layer (e.g. Nicking and Walker), the distance wind blows over the study area as a whole, and the distance the wind must pass over a sediment source before it is saturated in sand grains and starts depositing dunes.

In the original discussion of fetch (Sat Mar 27, 2004 6:21 pm) you said: "If these "dunes' were formed in this right (eastern) arm of the tri-radiate valleys as it is currently. then there would be no wind "fetch" distance or area of wind build-up to achieve sufficient force to form dunes in that reformed valley". This is use of fetch in an oceanographic sense, which does not apply to sand dunes. Wind needs to blow long distances over water to form large waves. Wind needs to blow only a few 10's of metres over a sand source to generate large dunes. This is much as a I said Sun Mar 28, 2004 5:09 am. It would be a good idea if we both specified which definition we are using.

Could you please provide references that explain why fetch is more important on Mars than on earth.

I have another question for discussion

6) What are your reasons for seeing convexity?

Yes, I know you think you have presented this before, but a summary under one heading would be useful at this stage of the discussion and helpful for newcomers.

Best wishes

Jon

Irishman

I depends how you use the word "see" I suppose. I can "see" why some perceive convexity. I may have seen convexity myself the first time, while recognising its illusionary nature and the true nature of the features in question. For me the illusion disappeared on inversion of the image, and I have never seen it since. I can "see" why some perceive convexity regardless of the orientation, becausing the curving dunes look like the curving lines used by artists to give the illusion of convexity on a two dimensional surface. But knowing this is not an artistic representation, where perceiving the illusion is an aid to understanding means that I do not see the convexity.

At the risk of introducing a red herring, this is analogous to the face on Mars. Some people perceive a face in patterns of light and shadow in a low resolution image of a Cydnonia mesa. I can see why they do so, but it does not mean that I perceive a real face there, quite the contrary. I see a mesa. Persisting in seeing a face is identical, IMHO to continuing to see real convexity in Acidalia.

Cheers

jon

I've only time now for brief responses to specific passages and not detailed arguments.

Where did JohnClarke find any statement in public release with direct reference to these tri-radiate valleys? What is the URL, please? I must have missed it. Or are you still referring to the "ridges (not dunes)" discussion made by Jon, again confusing the subject matter?



Still you are confusing conveying a 3D appearance in an anaglyph image with being a valid image. Presenting a 3D appearance via anaglyph is no great trick or mystery. However, the real question here is by what means canthese two images here be correlated so that any offset of features betweeen the two images (which results in a 3D appearance) is real representation and not a subjective choice or not the result of some methodology (such as mapping) which grossly distorts geometric relationships recorded in the original imagings? . Jon insists the anaglyph image is valid but steatfastly and repeatedly refuses to address the serious problem of the lack of correlation between these images.

They valleys themselves are not all that curious nor do the valleys themselves have any convex appearance. This area should be a non-issue and quite readily understood given commentaries in this thread alone. Yet curiously NASA/JPL chose to image the original image footprint almost exactly making no doubt that there is indeed a great degree of question regarding the image. While the high imaging angle in the second image enabled the duplication of the original imaging, that second image does not serve well in an anaglyph 3D representation as a result of the high imaging angle variance but it does provide a highly different perspective of the terrain under different lighting conditions and angle of view wherein NASA would hope and expect that 3D convex appearacne to no longer be present. Unfortunately that 3D convex appearance continues to be maintained.

Testable alternatives only come about from a resolve of what the evidence is and that is what we have been discussing in this thread here: what is able to be reasonably ascertained from the imaging evidence. Testable alternatives only come about when those details can be encompassed by known or hypothesized regimes. Any attempt to make all details fit any regime or hypothesis, ignoring incnvenient details, is only a superficial rush to judgement. Using comparisons of the perception of a "face" in Cydonia with this discussion only serves to prejudice and taint this disucssion, does not serve to advance any open discussion, and only shows a highly prejudiced approach. Similarly accepting such data products as the anaglyph as being valid at face value (irony intended) is not at all "working the problem scientificially".

I have already addressed this and other questions, Jon. My original response to your "testable alternative" challenge was, quote "How do you reasonably "test" a conclusion, such as "dunes", when the depth of the 'test" is the same as that which resolved the conclusion? (rhetorical) ".Your now repeated reiteration of all questions, both ignoring my answers and ignoring my own questions to you, does not further the discussion at all and only hobbles the discussion. Also your assertion that my failure to provide an alternative as not being "scientific" is objectionable, and itself represents a misrepresentation of the scientific process.

Wind needs to blow only a few 10's of meters over sand to gnerate dunes? This is a fallacy and you applying the concept of fetch limited by your oceanographic sense of the term. That wind needs far more terrain to achieve sufficent and sustainable velocity over time than "10's of meters". In discussions of water that amount of exposure of that water to an EXISTING wind is often considered, but not the sole consideration of "fetch". The merriam-webster dictionary defines the noun 'fetch" as: "a : the distance along open water or land over which the wind blows b : the distance traversed by waves without obstruction " While the achievement of sufficient wind velocity on earth it not such a necessary concern in study of dunes or waves, on Mars typical vind force is only sufficient at near gale velocities to reach similar force for dune formations seen on earth. On Mars this velocity typically requires channeling of winds into valley convergences or along other features which redirect ad accelerate wind direction, such as cliffs or scarps. There are many examples of this phenomenon in the Mars imagery, some of which have been discussed here, including Gorgonum Chaos.


My argument has never once been that the concavity (of the valleys) is an illusion. This is a misrepresentation on your part. Furthermore, given your own claim to understanding anaglyph imagery and recognition that the 3D effect is the result of offsets between comparative images, it should be a *GIVEN* that any feature can be represented or misrepresented as convex given false offets. This challenge is again irrelevant to the question of how one might correlate two so difergent images and still be able rely on the image geometries from which any and all 3D impresssions are derived in an anaglyph composite. You laid claim to the validity of the anaglyph. Surely any 'scientist" should be able to defend the process by which his "proof" is derived.

Jon, you stated, quote "Your refusal to answer question 4) suggests strongly that you don’t have the evidence, and that the alleged JPL correspondence is as fictitous... " In response I asked you if you were calling me a liar. My reasons for not providing direct reference to these emails have already been stated and also include no means to ascertain the validity of these emails by any source which is deemed credible by this forum. Despite this I have stated that these statements can be easily found via an internet search. Your evident failure to do such a search is not my problem. However if you do not find another tact with me in our exchanges, you and I will soon have serious problems that will prohibit any positive exchange from which others benefit.

Hi Tripp
If yours was a brief response, I would hate to see a long one.

With respect to your response to Q2: If these features are not dunes, how about you come up with testable alternatives?

In the image in question we see a Y shaped valley with transverse features. It is a reasonable hypothesis that these are dunes. We see such features in other Martian valleys and on earth. It is a testable hypothesis, because dunes in such a situation have a number of characteristic morphological features we can look for. If we find them, the hypothesis is strengthened, if we do not it is certainly weakened, if not outright falsified. Other explanations are certainly possible, can be similar tested. If you do not then I can only conclude you can’t come up with any or are unwilling to. Your choice mate.

You accusation of my ignoring your questions is one I take seriously. Please list the questions you feel I have ignored and I will attempt to answer them, just as I would like you to answer mine. However, I will not troll through 5 pages of posts to look for them as I will indubitably miss those you consider important (as indeed as I seem have done so already). I suggest you number them, as I have with mine, so we can keep track.

With respect to the distances over which dunes form
Dunes can and do form in 10’s of metres. If you go to a beach you will see dunes beginning to form within a few metres of the sand being dry enough to be mobilised by the wind. You see the same phenomenon with source bordering dunes, which develop similar distances downwind of dry river beds or lake floors. Provided the wind is sufficiently strong enough and there is a sand supply dunes can develop very quickly and over very short distances.

With respect to Q3 (as modified): What evidence (in the absence of MOLA and valid analyphs) would you accept as indicating the transverse features were dunes?

Please answer!

With respect to the analyph

You are misunderstanding what I am asking. My understanding of your argument is that while these are truly Y shaped valleys, their appearance as valleys in the” Mars unearthed” analgyph is meaningless because of the poor registration of the image. Furthermore, it would be possible to construct an anaglyph that could show these features as convex. Were you to do so it would strengthen your argument that the anaglyph is useless. So why don’t you do so or provide a link to someone who has?
Your response to Q4.

I have asked you repeatedly to provide evidence for this JPL correspondence. If you cannot produce it for a whole range of reasons (which can include valid ones such as confidentiality), then please say so, but if you can’t produce the evidence you should not have mentioned it the first place. Unsubstantiated references don’t advance the discussion. You should not be surprised when failure to deliver evidence as to their veracity when repeatedly asked leads people to draw negative conclusions.

Q5: Why do you accept the features in the other images as dunes and not these?

Once more, please list the specifics as to why the features I call dunes do not comply with aeolian mechanics.

Q6 What are your reasons for seeing convexity within the valley floors?

Your response is????

Best wishes

Jon

Yes, I am still referring to the "ridges, not dunes" quote that Jon found. As I said, this statement is similar to the statement you say you have in emails. Thus the relevance to this discussion. I realize it is not about this tri-radiate valley. That is my point - the comment above is not about the tri-radiate valley. If there is a similar comment by scientists that is about this valley, it has not been presented here.

I just went back to page 1. Funny, I find the person who brought up the JPL Media Relations Office comment from May 22, 2000, to be you.
http://www.badastronomy.com/phpBB/vi...=228879#228879

So I was not wrong when I thought that you indicated this comment was about these features.
And you refer to the same Media Relations Office comment here:
http://www.badastronomy.com/phpBB/po...=231774#231774


I went back to the beginning to find search terms to perform the internet search you said would easily let me find the emails in question. Instead I have found your comments stating that the JPL press release was referring to the tri-radiate valley system. Thus JonClarke's link to the context on the statement from this press release is valid, and it clearly shows the features they mean, and they do not mean this tri-radiate valley.

So how can you say you were not referring to the JPL press release, when in fact you were the one who first brought up the press release?

I did try a google search, could not turn up anything relevant. Perhaps I just don't know what to search for.

As I said before, "quote "How do you reasonably "test" a conclusion, such as "dunes", when the depth of the 'test" is the same as that which resolved the (original) conclusion? You are too busy repeating the same things again and again to ever engage in an disucssion with.


I gather you have not done much applied research or field work. To put it directly, even you yourself have cited a report by Malin & Edgett roporting on enigmatic ridge forms which are "not dunes" but the origin is not resolved. Also in the contested JPL Media Relations Offices statement there is the direct, clear statment, "Seeing Mars up close through the narrow angle camera has been a humbling experience. We often find surfaces for which there are no obvious analogs on Earth, like certain ridges that look like dunes. Our terrestrial geologic experience seems, at times, to fail us," IF NASA/JPL's Edgett and Malin are prepared to withhold conclusions in regard to some evidences on Mars (no matter to what they're referring) then perhaps it should be good enough for you too. When one engages in superficial evaluations based on "looks like" which ignore the finer salient image detail, it is not hard to reach conclucions such as "A face!" or other more commonplace evaluations, this does not mean they are supported when subjected to a more detailed, rational examination.


I have only reiterated the same question, rephrased again and again, sometimes highlighting that question in maroon colored text.



"So, Jon, specifically by what means do you maintain it is reasonable to correlate these two divergent images to make a 3D anaglyph? ) "

"Jon, are you so unable to recognize that the anaglyph is invalid that you must fabricate an irrelevant test for me to create yet another invalid anaglyph rather than respond to this fact? "


"JonClarke is not all concerned whether this anaglyph is "accurate" but is more than happy to reference it as 'proof" when it serves his case (which is no surprise given the creator)."

"Jon insists the anaglyph image is valid but steatfastly and repeatedly refuses to address the serious problem of the lack of correlation between these images. "[/i]

I was not addressing the "distances over which dunes form". This is only a limited definition of "fetch" in both common and technical usage. As shown by the non-technical application of the term "fetch" the Merriam-Webster dictionary has two definitions of the noun "fetch": : the distance along open water or land over which the wind blows b : the distance traversed by waves without obstruction " Fetch is not necessarily the distance of INTERACTION of the wind with a surface, such as "waves" in "b". Fetch, in its its larger unconfined definition involves the distance wind blows over land or water and represwents an unobstructed distance. In this regard it can also be made to apply to grain sources as they are involved in dune formation, but this is more limited definition and is understood within the context it is applied.

I have already answered the question twice now. You have even reiterated my response. WTF do you want?



Were I to construct an anaglyph showing the convexity of the "tubes" it would not at all strengthen my argument that the anaglyph is useless. Such a construction would only demonstrate how anaglyphs work, at best. Even if one were to take two images taken simulataneously from two seperate cameras seperated by an ideal angle of view, one could skew these two images and make false representations of the relief in an anaglyph composite simply by improperly offsetting the two images (which would be quite easily properly correlated).

Beyond that, as a "scientist" you should not be defending any data product as "proof" of anything if you do not have an intrinsic understanding of the product creation and its validity.


[quote="JonClarke"]I have asked you repeatedly to provide evidence for this JPL correspondence. If you cannot produce it for a whole range of reasons (which can include valid ones such as confidentiality), then please say so, but if you can’t produce the evidence you should not have mentioned it the first place. Unsubstantiated references don’t advance the discussion. You should not be surprised when failure to deliver evidence as to their veracity when repeatedly asked leads people to draw negative conclusions.

All of my resons for not providing the emails or a link thereto are valid and honest. The context in which I introduced these emails is only relevant to this debate because of your repeated claim you recognize no such overt apparent convex shape and did waste many posts back and forth seemingly deliberately misinterpreting what was asserted to be convex. I ony cited JPL's address of these features due to the fact these esteemed individuals do recognize the convexivity as being readily apparent although a "trick of light" or illusion. Were it not so readily apparent there would be no "trick" involved.

Because they maintain appearances within aeolian paramaters.

I already answered the question with specifics as you recognize yourself with "one more" . I do not need to do so here, now, again at your beckoning so you can yet again ignore the detailed references and continue to provide only useless generalizations with regard to earth and Mars. never addressing specific details. When I provide my argument it will be with supporting imagery to clarify that argument.

The fact I have made reference to the JPL Press Release in other conversations has nothing to do with my words from a conversation you youself were citing that was discussing the private emails of two persons associated with JPL. You were mistaken.

OK Tripp, we don’t seem to be getting very far. The discussion is in grave danger of bogging down in who said what, rather than in the nature of these features. At the risking of leaving some loose ends, I suggest we try a different approach to lead to a better understanding of these features. This is my goal; I hope it is yours also. This is what I propose:

First, we start complete fresh, ignoring everything said or done before.

Second, we work first from factual observations, and build up a suite that we agree on.

Third, after we have a good suite of such observations in hierarchical point form, we can move to hypotheses on how the features in question form. Fair enough?

There is the template to start with; we can add more headings and sub headings as required.

1 VALLEYS

1.1 Geometry

1.1.1 Four radial valleys, arranged approximately (N to the top) in 11, 2, 4, and 7 o’clock positions and labeled valleys A, B, C, and D, respectively

1.2 Scale

1.2.1 Valley A

1.2.2 Valley B

1.2.3 Valley C

1.2.4 Valley D

2 VALLEY FLOOR FEATURES

2.1 Valley Cross section

2.1.1 Valley A

2.1.2 Valley B

2.1.3 Valley C

2.1.4 Valley D

2.2 Valley profiles

2.2.1 Valley A

2.2.2 Valley B

2.2.3 Valley C

2.2.4 Valley D

2.3 Transverse features

2.3.1 Planar geometry

2.3.2 Scale

2.3.3 Albedo

If you accept this approach, put it in bold and add, in normal font, specific observations, specifying which image you see this in. If I agree with your observations, I will simply bold them and, perhaps, add some observations of my own in normal font. If I disagree I will not bold your observation and we can discuss the issue, as you would if you disagree with mine. Other people can, and I hope will, join in. We will use a consensus approach. For example, if two people disagree on an observation then it is in formal font, if two out of three agree on the observation then it is recorded as bold, but the minority opinion will be kept.

Best Wishes

Jon

Since we're discussing dunes and ridges and wind erosion... Here's some pretty clear examples... from this world. Note similar appearance, including wind driven ) shapes.

http://www.pbase.com/image/25610622
http://www.pbase.com/image/25967416

http://www.pbase.com/image/25967421
And to give you an idea of the scale, this picture features an airstrip
http://www.pbase.com/image/25967422

Awesome photos, akochan. Also, since you are very new here, welcome!

The photos are on unconfined dunes, of course but illustrate three different morphologies. the first is of transverse dunes, the second of draas (sand mountains, which are composite landforms an order of magntitude bigger than dunes), the last two of longitudinal dunes (I don't know if these have been seen on Mars).

Cheers

Jon

I was at work so I didn't have time to do any real serious photo hunting, but if I find any confined dune/wind photos I'll post links to those too.

Thanks for the welcome.

There are plenty from MGS of Mars.

Dunes in a channel - MGS's "Mars Picture of the Day" for today.

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Everything I need to know I learned through Googling.

Just a small thought:

If these are actual tunnels and as Hoagland thinks, have "cars" trapped inside them...where are the other cars? Where are the stations? Where are the suburbs? The tunnels had to go from somewhere to somewhere else...so where are those places?

Surely if huge glass tunnels, miles long can survive, evidence of those people that built them can survive, along with their homes and businesses.

Oh wait, apparently all the martians did was build huge faces and weird tunnels. Oh, and pyramids. No actual cities, no suburbs, not one shred of any real technological apparatus. No evidence, in fact, that Mars ever had any kind of atmosphere to support towns and schools and tunnel-building universities.

Still amazes me, the lack of critical thinking on this planet.

OP: Now we have MRO's take on at least one dune-filled canyon, no doubt the first of many: Aram Chaos

(Google Mars for context)

No glass tubes. No giant worms. No shiny ice. Just marvelous dunes in a canyon.

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Hoagland is the internet's own comedy relief. He's just like one of those people that gets all excited over an obvious pyramid scheme. And when you try to explain it to him, he won't listen and think you're just trying to hold him back.