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Unmanned Spaceflight.com _ Mars _ geology of Gale Crater and Mount Sharp

Posted by: David Palmer Jun 21 2014, 01:49 PM

The idea that the Lower Formation of Mt. Sharp is of lacustrine origin (lakebed sediments) has rather fallen out of favor recently, but I just finished my essay on Mars, "An Interpretation of the Geology of Gale Crater & Mount Sharp, with Implications for the History & Habitability of Mars," which I have spent over one year researching and writing, and the primary thrust of this paper is to offer a fresh defense of the lacustrine model, incorporating some fairly original ideas on my part. I'm not a professional scientist, but this is a labor of love that springs from a near-lifelong interest in Mars (since I was a young boy in the 1960s). And I'm trying to publicize it prior to Curiosity reaching Mt. Sharp, as that will be a test of my theories, and I'm hoping to get some recognition if I'm right. So here's the link for all interested readers: http://galecratergeology1.tumblr.com/post/85407991682/an-interpretation-of-the-geology-of-gale-crater-mount

Posted by: PDP8E Jun 21 2014, 08:23 PM

Hi David,

What A fact filled first post!
Your paper is thought provoking, and I was surprised to find part 2, 3, and 4 after I finished reading the first!
Thanks for sharing and we shall see how your theory fits reality in the coming weeks, months, and years.
(I always thought those channels looked young!)

NOT SWEET! (read it to find out!)

cheers!


Posted by: elakdawalla Jun 23 2014, 03:33 PM

Hi David, it's clear you've put a lot of work into this. I do think you need to recognize the work of others by labeling the images on your pages with the missions and institutions that produced them. A partial list of who should be credited for data of various kinds can be found on http://www.planetary.org/explore/space-topics/space-imaging/copyright.html.

And this piece of advice is not just for you, but for any non-professional who wants to have their ideas on science taken seriously. It's important to demonstrate that you take other scientists seriously as well. In science you do that by demonstrating an awareness of what other people have written on the topic. Some of what you've written here likely agrees with other scholars; some disagrees. It's on you to show where your ideas fit in -- whose previous scholarship do you agree with? Whose are you contradicting? What specific arguments can you make that demonstrate that your ideas hew closer to the truth than the ones you're contradicting? You certainly wouldn't be the first to talk about lakes within Gale crater, or to map the heights of deltas! There is http://adslabs.org/adsabs/search/?q=title%3A%22gale+crater%22&month_from=&year_from=&month_to=&year_to=&db_f=%28astronomy+OR+physics%29&nr=&bigquery=, as I'm sure you know. It's one thing to chitchat on a forum, but if you want to join the scientific conversation you have to listen to what others have to say and make counterarguments, and you demonstrate that you've listened to what others have to say by citing previous work in the area. I don't see a single citation on your page, so what you have right now is a thoughtful and well-illustrated blog entry, not a scholarly contribution. You don't have to be a professional to make a scholarly contribution, but you do have to respect the work of others in order for them to respect yours.

So the next step, if you want to be taken seriously, is to cite previous work, and then distill this into a 2-page abstract and submit it to the next Lunar and Planetary Science Conference; the abstract deadline is usually right around the end of the year. There's no requirement that you be a professional to present work at a conference. Choose a poster presentation rather than a talk; the conversations around posters are much more fruitful.

Posted by: PDP8E Jun 23 2014, 09:01 PM

my post (above) seems to have replicated itself...
was that the glitch?

Odd - I've removed the duplicate text. - Mod

Posted by: David Palmer Jun 23 2014, 10:45 PM

QUOTE (elakdawalla @ Jun 23 2014, 08:33 AM) *
Hi David, it's clear you've put a lot of work into this. I do think you need to recognize the work of others by labeling the images on your pages with the missions and institutions that produced them. A partial list of who should be credited for data of various kinds can be found on http://www.planetary.org/explore/space-topics/space-imaging/copyright.html.

And this piece of advice is not just for you, but for any non-professional who wants to have their ideas on science taken seriously. It's important to demonstrate that you take other scientists seriously as well. In science you do that by demonstrating an awareness of what other people have written on the topic. Some of what you've written here likely agrees with other scholars; some disagrees. It's on you to show where your ideas fit in -- whose previous scholarship do you agree with? Whose are you contradicting? What specific arguments can you make that demonstrate that your ideas hew closer to the truth than the ones you're contradicting? You certainly wouldn't be the first to talk about lakes within Gale crater, or to map the heights of deltas! There is http://adslabs.org/adsabs/search/?q=title%3A%22gale+crater%22&month_from=&year_from=&month_to=&year_to=&db_f=%28astronomy+OR+physics%29&nr=&bigquery=, as I'm sure you know. It's one thing to chitchat on a forum, but if you want to join the scientific conversation you have to listen to what others have to say and make counterarguments, and you demonstrate that you've listened to what others have to say by citing previous work in the area. I don't see a single citation on your page, so what you have right now is a thoughtful and well-illustrated blog entry, not a scholarly contribution. You don't have to be a professional to make a scholarly contribution, but you do have to respect the work of others in order for them to respect yours.

So the next step, if you want to be taken seriously, is to cite previous work, and then distill this into a 2-page abstract and submit it to the next Lunar and Planetary Science Conference; the abstract deadline is usually right around the end of the year. There's no requirement that you be a professional to present work at a conference. Choose a poster presentation rather than a talk; the conversations around posters are much more fruitful.




Excuse me, but I cite 66 references in my essay! In fact, that part of my essay is something I put a great deal of work into, it was one of the most time-consuming parts of the process. And as regards the pictures, I state at the beginning of the references, "All photos courtesy of NASA/JPL unless stated otherwise." And when a figure is not from NASA, I do credit it when talking about the figure in the text.

One thing I do differently in my essay, as compared with most academic papers, is to not give captions for the pictures, but to place those pictures directly in the location where I am talking about them. This is in response to something I have found INCREDIBLY irritating about most scientific papers, having to go back and forth in the document to see the figures being referred to. I aimed to make it flow a lot smoother, to read a lot easier.

Dave

Posted by: djellison Jun 23 2014, 11:49 PM

QUOTE (David Palmer @ Jun 23 2014, 02:45 PM) *
And when a figure is not from NASA, I do credit it when talking about the figure in the text.


You've included images that I know are not NASA's that do not have a credit in the text, next to the image, or anywhere else.

There is no way to know if an image is NASA's or not.

Moreover - the images that do originate from NASA - "All photos courtesy of NASA/JPL" for most of the images you use - that is an insufficient and in many cases an incorrect credit.

Just one example - the last image of Page 1 is clearly an HRSC image. I see no credit whatsoever.

The image credit should, at the very least, be

CODE
ESA/DLR/FU Berlin


And more properly in a publication should be

CODE
G. Neukum, R. Jaumann, and the HRSC Co-Investigator and Experiment Team, HRSC: The High Resolution Stereo Camera of Mars Express, in Mars Express: The scientific payload, edited by A. Wilson, pp. 17-35, ESA, Noordwijk, The Netherlands, 2004.

R. Jaumann, G. Neukum, T. Behnke, T.C. Duxburry, K. Eichentopf, S. van Gasselt, B. Giese, K. Gwinner, E. Hauber, H. Hoffmann, A. Hoffmeister, U. Köhler, K.-D. Matz, T.B. McCord, V. Mertens, J. Oberst, R. Pischel, D. Reiß, E. Ress, T. Roatsch, P. Saiger, F. Scholten, G. Schwarz, K. Stephan, M. Wählisch, and the HRSC Co-Investigator Team: The High Resolution Stereo Camera (HRSC) Experiment on Mars Express: Instrument Aspects and Experiment Conduct from Interplanetary Cruise through Nominal Mission, Planetary and Space Science, 55, 928-952, 2007.


If you want to retain flow.... put a one line caption and credit with every single image.

It also is very very easy to miss your references, because they're only at the end of the fourth webpage. Ideally - they should be at the bottom of each section as appropriate.

Posted by: elakdawalla Jun 24 2014, 12:09 AM

Ah, my mistake, I did not notice the list of references on the fourth page. The essay is not organized like a typical paper, so I got a little lost -- observations and inferences are all mixed together. On a closer second reading I see you considering models one by one. You're missing any of Malin and Edgett's mapping work on the crater and other mound-filled craters.

Almost none of your photos are from NASA/JPL alone (only Viking and the rover Navcams and Hazcams have that credit, without other institutions like UA for HiRISE or MSSS for Mastcam images). I see at least one photo of mine, which has data from MRO CTX and Mars Express (MSSS and ESA/DLR/FU Berlin (G. Neukum)). I believe that there are several other amateur-processed images in your essay but I cannot be certain because they are not labeled as to their source.

I think there are a few really good points in here about inconsistencies in relative timing of events being described by different researchers, points that they should listen to and think about. But the way that this essay is structured, no professional will read it.

Scientific papers have a typical structure and signposts to that structure that really helps a reader. You have an introduction and literature review section, briefly summarizing past work -- here would be a great place to identify the specific logical inconsistencies you have found in those stories. You have a methods section, identifying your data sources and how you went about doing your research -- it should be devoid of interpretation, focusing on the locations of the geomorphic features you are mapping: craters, channels, boxwork, shorelines, etc. Then lay out your two models (the story you tell about the order in which formation and erosion happened for all the geomorphic features you identify in the previous part). Then have a discussion section where you compare your model to others' models -- you have a choice here: you could compare your model to other models one by one, or take geomorphic features one by one and compare all models' explanations for them. Your essay sort of does the latter but we keep coming and going to features and I lose the thread of your argument. Finally you wrap up with conclusions, which may include a section that identifies specific tests of your models. All this stuff is in your essay but it's mixed up, and there's a lot of irrelevant material like your discussion of Martian sky color.

This organization is important, because as a reader I cannot keep everything in my head as I read. I will read, and get partway through, and need to return to literature review and observation and model sections to remind myself of stuff as I read your discussion section. Right now you have a little bit of observation, and some discussion, and then comparison to one paper, and then some different observations, and then discussion, and I'm sorry, but I find it very hard to follow.

Posted by: djellison Jun 24 2014, 01:20 AM

QUOTE (elakdawalla @ Jun 23 2014, 04:09 PM) *
I'm sorry, but I find it very hard to follow.


I tried - and I'm afraid I had to give up.

You've clearly done a lot of work David - but the devil is in the detail when it comes to gaining professional traction.

Posted by: Juramike Jun 24 2014, 04:05 AM

You've put a huge amount of work into this. I encourage you to push it just a few more yards to get it over the goal line. If it's not in the peer-reviewed literature, it doesn't count. (Gray literature can't be cited in many journals.) Worse, someone else can take the ideas, do the extra effort, and get the credit for it.

I encourage you to distill it down to your best concise story ("the slam dunk"), get really, really hardcore tight with the data ("How do I know what I know?"), get really, really hardcore tight with the interpretations ("Can I prove this to a court of hostile scientists?"), and try to find every single reference relevant your research ("On the shoulders of giants"), and submit as a short paper. As you move forward, you may need to tweak the interpretation to fit the observations, or that the evidence doesn't support the interpretation (in which case it's just speculation, and won't hold up to peer review.) In some cases, you may need to modify, scale back, or even abandon the paper.

Most importantly, as Emily mentioned, the key parts of any paper are Introduction - Materials and Methods - Results - Discussion - and Conclusions. That formula works well and allows reviewers and readers to critically evaluate the paper for each step. (Personally, as a lab guy, I think the Materials and Methods section is the most important part. If it is not clear what original work was done, and how it was done, and why that method is valid, then the rest of the paper is weakened.)

For a few suggestions to getting it ready for submission, I'd suggest a reference style where the author names and years are in-line with the text, such as: "blah-blah-blah (Smith et al., 2010)." Or: "As recently described in Smith et al., 2010, blah-blah-blah." Saves having to keep track of reference numbers, and many readers might already be familiar with the references and then don't need to page back to the end of the text or poke around in the footnotes. References are your friend: if someone else has already published something in the literature, you aren't (totally) responsible for defending those concepts. The goal is to minimize exposure. A truly brilliant piece of work uses concepts already in the literature to weave a beautiful tapestry.

Figures should also have a complete as possible caption, and have citations and have the sources acknowledged. They should also be referenced in the text. I like a style that keeps them in-line for the manuscript. (You can sometimes get away with that for the first cycle of peer review.).

An LPSC abstract follows the same rules, but has to pack everything down to two concise pages.

For the record, my first foray into submitting a manuscript in planetary science many years ago was appropriately slammed in peer-review. It was a humbling experience, but ultimately helped me become a better scientist. ("Agressive baserunning, conservative fielding...")

Go for it! And good luck!

Posted by: serpens Jun 24 2014, 08:04 AM

Firstly let me congratulate you David, on the level of effort you have put in and I appreciate that this is meant to be an essay rather than a formal paper. Consequently the referencing for papers etc. can simply be a bracketed reference number in text relating to the references summary. Certainly in many articles and papers, including LSPC, authors do not necessarily reference the provenance of images. Still it is polite to do so but make it a list of figures else the referencing clutters the document and you lose continuity. I enjoyed reading this although the format and layout presents a real challenge and the flow of logic is pretty disjointed. All in all it was a bit of a challenge. I am not sure what your end objective is; publication, presentation at a scientific forum or exposure on forums such as this. Regardless, Juramike has pretty well summarised my feelings on layout and presentation, although I suspect that to some extent your format is suffering from the vagaries of Tumblr which is not really a vehicle of choice. Visual presentation and structure is extremely important and it would be sensible to convert the document to .pdf. I would suggest that you don't let ego get in the way, treat this as preliminary draft and start the process of rewriting which is unfortunately an integral part of paper writing. The end results will be worth it.

Enough on presentation. While I don't think that you actually present any new concepts you are trying to present your insights as a cohesive hypothesis, addressing Gale crater as a whole and an effort such as yours deserves a well considered response. I intend to try and sort out (in my own mind) your propositions over the next week or so and I will correspond directly with you by email. Would you mind letting me know your address on the forum messaging system?

Incidentally, I would suggest you use the metric system as opposed to feet.

Posted by: David Palmer Jun 24 2014, 02:08 PM

In response to Serpens:

My intention with my essay is purely noncommercial, it is basically a hobby thing on my part, and the more people I'm able to share my ideas and enthusiasm with, the better. The "publishing" of my essay is first and foremost exactly what I am doing here, posting it in online venues with intelligent people who share similar interests (however, Mars Journal has expressed interest in this paper, if I am able to come up with a 15-or-so page summary of my ideas to present in conjunction with the full-length essay).

I have to disagree when you state that I have no original concepts, as no one else has proposed an "artesian hydrant" in Mt. Sharp, and no one else has suggested that there was major fluvial activity (and a lake) in Gale Crater in the recent geologic past (and I discuss the testing of these hypotheses in the section aptly titled, "Testing My Hypotheses," at the start of part 3....it now appears that the time of reckoning will be early 2015, when Curiosity reaches the lower reaches of Mt. Sharp).

One of the purposes of my essay was to not only present my ideas, but to capture the beauty of Mars, and I'm rather surprised that Emily can't relate to my approach, and rather roundly criticizes my essay, since I thought I was doing something in the vein of the blogs she presents, both in terms of the level of (non)technical discussion, and in terms of aesthetics (only on a larger, more ambitious scale). Possibly some of the critics of my essay don't understand exactly what I am trying to accomplish here.

My interest in Mars was originally stimulated when, in the 1960s, I encountered "The Exploration of Mars," featuring the artwork of Chesley Bonestell. And I wanted to be a space artist for a while, but that didn't work out, so the next best thing was to wait till there was enough gorgeous photography available.....which we now have, and which fortuitously coincided with my having some original ideas I wanted to run with. And when I had my ideas a little over a year ago, I figured it might take a couple of weeks to write a paper....little did I know! I ended up having to read hundreds of articles and papers on Mars and Gale crater, many of them rather technical, to feel I had done adequate homework.

The logic I present may be rather hard to follow because the subject matter is so vast (the only paper on Gale that I can think of that approaches this scale is Anderson and Bell's, and they just do a piecemeal analysis of individual features without driving towards an overarching conclusion), and everything in my paper ties together as part of the whole (except for the two tidbits I placed at the end, Notes on the Sky Color of Mars and The Future of Humanity on Mars....that's just bonus material I added, because I thought I had some significant things to say and could also use it as an excuse to further indulge in the presentation of gorgeous pictures).

I basically present my main hypothesis (a recently active artesian hydrant) at the beginning of the essay, where I offer some of the more direct (and interesting) arguments for it (such as the morphology of the channels), and the latter part of my essay is mostly spent elaborating on this idea from different angles, bringing in additional supporting evidence from a wide-ranging survey of Mt. Sharp and Gale Crater, and addressing competing models and demonstrating their shortcomings (and in some cases, taking data that was used to support a competing model, such as SWEET, and showing how it actually supports the lacustrine model). And I was particularly pleased with how I sketched out a new interpretation of cratering frequencies and age determination, and brought in the recent evidence that the crater production function has NOT been nearly constant over time, and the implications that has for Gale.

I am of course going out on a limb in presenting these ideas, but I believe I have outlined a model that is compatible with all known data and explains all of the geomorphology of Gale and Mt. Sharp, whereas the competing models all have internal contradictions, and conflicts with the empirical data.

And you're right, Tumblr has definite limitations, and my essay is NOT formatted the way I originally intended it.....Tumbler definitely has a mind of its own. For one thing, my original manuscript had "block" paragraphing, with spaces between paragraphs. But when I copied and pasted into Tumblr, it eliminated the spaces, and wouldn't let me add them back, so my only recourse was to do the old-fashioned indentation thing. PLUS, I couldn't do the wide panoramic pictures I did in my original manuscript (which in some cases were much wider than the text), so I had to resort to cropping and zoom shots. And, the image resolution on Tumblr is lower than in the original pics.

But the reason I used Tumblr was that I felt I was under the gun and needed to get my essay out there well before Curiosity reached Mt. Sharp, and lacking as I do experience with setting up websites, I needed to work with what I was readily able to figure out, and I didn't have the money to pay someone else to set up a website, and all the other do-it-yourself sites that I checked out, fell even shorter of giving me what I needed. So I worked with what I had.

The reason I mix and match Metric and English, is that I wanted the essay to also be accessible to people who are not fully comfortable with the Metric system yet. This essay makes the attempt to straddle a number of fences (as another example, I only get as technical as I have to, in conveying my scientific ideas), so it can't really be expected to conform to the mold of an academic journal paper.

My address for direct e-mail is RainBoKatchr@aol.com

Dave

Posted by: elakdawalla Jun 24 2014, 06:18 PM

My apologies, I completely misread your intent. When you said "And I'm trying to publicize it prior to Curiosity reaching Mt. Sharp, as that will be a test of my theories, and I'm hoping to get some recognition if I'm right" I interpreted that to mean that you were advancing scientific hypotheses for which future Curiosity work would be a test, and you wanted recognition of your scientific contributions if you were right. It seems like that's what you intend; on page 3 you say:

QUOTE
However, dating the cosmic ray exposure age of the channel fill should be exceptionally interesting, and is likely the single most important test of my hypotheses that Curiosity can perform. For if it shows the low exposure age that I am predicting (several million years, or even less in areas subject to a higher-than-average erosion rate), it will confirm both my SAH and YCL hypotheses: that the formation of the Northern Channel’s fill (and hence the occurrence of the Second Generation Lake) was not only a recent geological event, but also had to be a product of the artesian hydrant mechanism I am proposing (as there is no other conceivable source for such a large volume of water within such a recent timeframe).
I interpreted this to mean that you intend to advance your scientific hypotheses among the professional community. That was the basis of my criticism, and I apologize for its harshness because it simply doesn't apply if you're just writing a blog where you have fun discussing features of Gale crater.

So, if you don't actually seek any interest from the scientific community, then almost all of my comments above don't apply. The one thing that does apply is that you need to credit your image sources properly, especially the non-NASA and amateur-processed ones. (NASA images are in the public domain, but ESA ones are not, nor are any "derivative works" of NASA images, including ones published in professional journals.) You've got a fine blog about Gale crater -- a year's worth of blog posts strung end to end. You might get more attention to it from other members of the amateur community if you split it into many, many pieces and posted them as more-digestible blog posts with good titles for each entry; that'll help search engines find you. Do it on Wordpress; it's a much better platform for blogs than Tumblr is.

I agree with Mike that there are some things in here that could be of interest to the scientific community, if that's really what you want to do. But I disagree with him that it's ready for you to rewrite and submit for peer review. I think you would profit a great deal by pulling out your model and your explanations of logical inconsistencies in others' work and putting that in an LPSC abstract and going to LPSC and inviting comment and listening to what scientists have to say.

Posted by: djellison Jun 24 2014, 08:59 PM

Of the entire 4 page work - this is the part that I find most obviously factually incorrect....


From section 4 - "there are actually very few perspectives within Gale that show the sky directly above the horizon"

This is patently false. Every image you include after that comment has the sky in it. Every. single. one. There are hundreds - hundreds and hundreds that do - as well as the end-of-drive MAHLI postcards that get taken after each significant drive. Your claim is just totally false.

"NASA now seems to have wised up to what the actual sky color of Mars is, has quietly dropped its former references to the “pink” or “salmon” sky of Mars, and recently there have been photos and panoramas released from earlier surface missions, apparently re-calibrated, that show a green-tinted sky similar to Curiosity’s"

Also false - and the images you include are not NASA's - infact, I think they're Olivier de Goursac's - but you don't credit him appropriately. Many are manual colorizations of navcam mosaics.

And finally - I'm really not sure how it's possibly attempt to conduct a discussion on the color of the Martian sky without including references such as...

BELL ET AL.: CHROMATICITY OF THE MARTIAN SKY
http://marswatch.astro.cornell.edu/Bell_etal_SkyColor_06.pdf

or
MAKI ET AL. : The color of Mars: Spectrophotometric measurements at the Pathfinder landing site
http://onlinelibrary.wiley.com/doi/10.1029/98JE01767/abstract

You can have you own opinion - but please don't simply brush aside careful scientific analysis because it doesn't match your opinion. That's not scientific. If you think they're wrong - then you have to do the work to explain why. 30+year old anecdotes that have nothing to do with Pathfinder, Spirit, Opportunity or Curiosity do not constitute scientific discourse.

Posted by: mcaplinger Jun 24 2014, 09:56 PM

QUOTE
a green-tinted sky similar to Curiosity’s...

Moreover, as has been discussed at length on this forum, the green tint is largely if not completely an artifact of the Mastcam IR cut filter bandpass, and is not a real feature of the martian sky.

Posted by: fredk Jun 24 2014, 10:10 PM

mcaplinger beat me - I was going to link to http://www.unmannedspaceflight.com/index.php?s=&showtopic=7418&view=findpost&p=208388 and surrounding discussion on the green cast. Just having a colour CCD on the surface doesn't necessarily tell you very accurately what the colours are, as anyone who's taken a picture with a bad whitebalance setting knows.

Posted by: David Palmer Jun 24 2014, 10:43 PM

QUOTE (mcaplinger @ Jun 24 2014, 01:56 PM) *
Moreover, as has been discussed at length on this forum, the green tint is largely if not completely an artifact of the Mastcam IR cut filter bandpass, and is not a real feature of the martian sky.



I DID state that the actual sky color of Mars is near-neutral, and thus that any liminitations in the instrumentation, or slopiness in the processing of the data (or its ultimate display on a monitor) will skew it towards either the red or green or blue....and it is clearly the case that the earlier (especially Viking) images over-did the red. This is confirmed by the fact that Mars doesn't look that red in a telescope....it is actually a slightly ruddy yellow.....similar to desert terrains on Earth.

Posted by: djellison Jun 24 2014, 10:51 PM

QUOTE (David Palmer @ Jun 24 2014, 02:43 PM) *
I DID state that the actual sky color of Mars is near-neutral,


And this 'statement' is contrary to the two peer reviewed articles I cited above. Despite being from different scientists using instruments on different spacecraft, 7 years apart, on different parts of the planet - the Pathfinder and MER (both A and B ) results are in excellent agreement regarding the color of the sky on Mars.

Posted by: David Palmer Jun 24 2014, 11:05 PM

QUOTE (djellison @ Jun 24 2014, 12:59 PM) *
Of the entire 4 page work - this is the part that I find most obviously factually incorrect....


From section 4 - "there are actually very few perspectives within Gale that show the sky directly above the horizon"

This is patently false. Every image you include after that comment has the sky in it. Every. single. one. There are hundreds - hundreds and hundreds that do - as well as the end-of-drive MAHLI postcards that get taken after each significant drive. Your claim is just totally false.



My reply:
This is NOT correct....because any perspective within Gale Crater is ringed by hills. I never did say that sky wasn't showing in the pics....just that the sky DIRECTLY above the horizon is cut off. So the above comment involves a misreading of my statements. Also, I explicitely stated at one point that the photo I was describing only created the illusion of sky, that there were hazy hills in the background (it almost looks like sky, but you can see the outline of hills if you look close)....so it is incorrect to say that every image I include has sky.

And in fact, most of the photos I use ARE NASA's.....taken directly from the "raw image" files at http://mars.jpl.nasa.gov/msl/. The Olivier de Goursac panoramas are put in as a bonus (to be pretty), and are not what I'm basing my primary conclusions on.

In any case, I AM doing additional work on giving credits for images, so that is a valid criticism of my essay....this has been a work in progress for one year now, so it's not surprising that it needs some additional tweaking.

Posted by: serpens Jun 25 2014, 12:30 AM

I think perhaps everyone needs to take a deep breath and have a nice cup of tea. Colour by definition is a human perception of reflected frequencies and that perception can differ to a degree between individuals. So the human perception of the colours of Mars, after selective frequency transmission and tweaking should best be described as a very good approximation and really is not worthy of this type of argument.

The "artesian hydrant" scenario you refer to would correlate to a spring mound effect and this has been considered previously as a possible influence on the development of Mount Sharp, but is considered a very low probability. For instance Figure 2 of the 2013 paper by Kite et al "Growth and form of the mound in Gale Crater, Mars: Slope-wind enhanced erosion and transport" provides a good comparative illustration of the stratigraphy expected from various influence forming Mount Sharp, including spring mounds. The thing with Gale is that we are looking at an erosional end state and really do not have a clue as to the structure of the crater, or floor depth when some of the features you discuss were formed. But if we consider the lower (seemingly non Aeolian) layers of Mount Sharp in the light of Mr Steno's rules and the apparent structural strength of some of the sedimentary rock observed by Curiosity then at some time there was a lot of material above the current floor that Curiosity is traversing. Despite the exceptional capability of orbital imaging and Curiosity's ground truth , the scope of "hands on" analysis is very limited. This means that even after Curiosity investigates accessible parts of Mount Sharp there will probably be multiple hypotheses alive and well at the end of the day, including possibly some of yours.

You make some good observations and interpretations but perhaps should revisit potential alternative influences. In analysing Gale I think it is necessary to consider it in the context the surrounding region and the somewhat unique North South crater rim height difference due to the position on the dichotomy boundary. There is reasonable evidence that a Mars Ocean existed, possibly a couple of ocean recharges, and that would have implications for partial flooding of Gale from an aquifer.

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Posted by: David Palmer Jun 25 2014, 01:22 AM

reply to Serpens:
I am very aware of the spring mound hypothesis and discuss it in my essay, and state that it could have contributed to the core of Mt. Sharp, but Rossi et al. envision Mt. Sharp being built of evaporate deposits, and of such activity being confined to the early geothermal phase of Gale Crater, so it is a different hypothesis from mine, where I am claiming that the artesian hydrant is an ongoing phonomenon that was active again fairly recently. And while the northern ocean would indeed have filled Gale Crater, I am claiming (on the basis of the Mt. Sharp channels and their delta deposits) that a deep lake existed in Gale LONG after that ocean had dried up. And the natural interpretation would be that a still-active aquifer occasionally commutes to the surface when conditions are right, the water table of which can be calculated to be well above the half-way point of Mt. Sharp on the basis of the surrounding terrain and the geologically recent Cerberus Fossae outflows.

Dave

Posted by: vikingmars Jun 25 2014, 02:45 PM

About the color of the Martian sky : we had already this debate loooong ago in 1982 while processing the Viking Lander 1 images from its Monitor mission at the IPL in JPL. The two scientific papers cited hereabove (Bell et Al.: "Chromaticity of the Martian Sky" and Maki et Al. : "The color of Mars: Spectrophotometric measurements at the Pathfinder landing site") truly depict the real colors of the Martian sky which could be referred globally as a "salmon pink". However, the saturation of its color depends a lot on the quantity of dust (aerosols) suspended into the atmosphere : as you know, it can vary during the seasons.

Here is a processing done over 999 Sols with images from the VL1 Monitor mission that show the variations of dust suspended in the atmosphere over its landing site. Although the sky may look "blue"” to your eyes 30° over the horizon, this is an artifact done by the processing of your brain : a problem also identified long ago also by the astronomers watching the Red Planet through their telescopes. Now, if you sample carefully the colors of the sky 30° above the horizon, when the dust opacity is at its minimum (Sols 1335 and 1957), you will notice that the Martian sky never loses its salmon pink hue. It’s only much less saturated than normal and only tends to be more "grayish". But, it always keeps its "salmon pink" color just above the horizon.
So… the Martian sky is definitely NOT blue !

PS : There was a huge dust storm blowing over the VL1 lander on Sol 1742 : this explains why you see a reverse in the luminosity of the sky.


Posted by: serpens Jun 27 2014, 03:44 AM

Dave, I am answering here rather than by email because I would be interested in the take of a few of the extremely knowledgeable posters on this forum. Note by the way that I said influenced by spring mound effects, not that this is a sole cause. When I suggested looking at a regional context I was considering the topography surrounding Gale, in particular the North and North West which indicates significant erosion and indicates that that Gale was possible once covered to a regional level above the crater rim and then exhumed. If so we have to consider that the channels originating on Mount Sharp could be the end remnants of drainage channels that originated well outside the crater when the crater was filled to a common level. Erosion and exhumation of the crater and Aeolian deposition of the higher section of Mount Sharp would have removed any evidence. The implication of course is that any lake corresponding to the Mt Sharp deltas would have been quite shallow. There are remnant channels all over the area and in generating hypotheses on Gale we have to consider every possibility with respect to the changing regional terrain over many billions of years and the fact that we do not really have a clue as to the actual environment when some of these features formed. Atmospheric pressure, temperature, wind speed or water content. My take is that for a reasonably long period it was one heck of a dynamic environment and the topography of Gale and surrounds was nothing like it is today. There are lots of potential hypothesis for gale and the evidence of a lacustrine environment and I throw the above in simply to point out that every possibility has to be considered.

Posted by: David Palmer Jun 27 2014, 04:07 AM

reply to Serpens:
The basis of my argument for the artesian hydrant in Mt. Sharp, is that the deltas (in particular the delta deposit of what I have christened the "Northern Channel," which Curiosity is now driving towards) would have been long-since worn away unless they were very recent, given the measured wind erosion rate in the local environment (low crater retention ages as calculated from orbital imagery, and also in-situ measurements of wind erosion rates by Curiosity). So these channels had to flow, and their deltas be deposited, when the topography of Gale, Mt. Sharp, and the surrounding terrain was essentially as we see it today. If there had been more than several hundred vertical feet of wind erosion (which appears to be only several tens of millions of years worth), any trace of those deltas would be gone.
And another reason that these channels could not have been part of any regional drainage system, is that they are oriented radially on the sides of a more-or-less conically-shaped mountain, so the mountain had to be the source of water.

Dave

Posted by: David Palmer Jun 27 2014, 09:35 AM

reply to vikingmars ("About the color of the Martian sky"):

I never did say that the Martian sky was blue, rather that under CLEAR conditions it is close to neutral or grey. And when I refer to the "sky," I am considering the full dome of the sky, not just the area several degrees above the horizon. Just as on Earth, if there is white or brown haze near the horizon, we still say that the sky is "blue," not that it is white or brown, because blue is still the dominant color in the dome of the sky. But when we have a lander that is predominately photographing the landscape, a bias tends to be created such that the color of the sky just above the horizon, is psychologically perceived to be the defining color of the sky (in this case pinkish beige), because that's the only part of the sky showing in most photos, whereas if we were to step out onto the Martian surface and gaze upwards, we would take the color occupying the greater part of the sky's dome to be the defining color.....which in the case of Mars, is a mix of beige and grey or blue-green, under clear conditions, and better yet, at a below-datum location such as Gale Crater, where there will be more Raleigh scattering of the blue end of the spectrum. Also at Gale, the pinkish beige area just above the horizon is usually cut off by the surrounding hills.....so the net result at Gale is a fairly bright sky (even at the zeneth) that is usually a cross between beige and blue-green. The above examples that you site from the Viking 1 lander, have a darker sky under clear conditions than we ever see in Gale, due to the higher elevation and less of a total gas column, but under clear conditions I would still rate the Viking 1 sky as grey, or even blue-grey (and this is not due to the chromatic contrast issue that you mentioned....when I take pieces of paper and hide the surface and lower atmosphere in the illustration you provide, the higher areas under clear conditions still look bluish-grey to me).

NASA now seems to have realized their earlier failing in making the Viking photos WAY too red, and they have recalibrating photos archived that are said to approximate what a person would see on Mars, and they can be found at http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-mars.html
You will note that in some of these Viking photos the sky is green and in others grey (NOT red or orange or pink as in the old releases).

Dave

Posted by: scalbers Jun 29 2014, 06:40 PM

I can point here to my post in another thread, where the brightness and color of Martian sky is simulated considering both Rayleigh scattering from the air molecules and Mie scattering from typical amounts of dust. Here it does look salmon/gray when one is away from the horizon and the sun. I haven't actually looked on a color diagram with some of the pixel values yet though.

http://www.unmannedspaceflight.com/index.php?showtopic=6248&pid=206891&st=30&#entry206891

A back of the envelope calculation suggests the scattering from the dust aerosols would be roughly 16 times as much as the scattering from the gas part of the atmosphere in the darkest parts of the sky. I'm assuming aerosol optical depth is 0.2 on my envelope.

Posted by: marsophile Jun 30 2014, 04:02 AM

Given the wide variation in the amount of dust, perhaps one should be wary about drawing conclusions from a calculation for one specific ("typical") level of dust.

Posted by: mcaplinger Jun 30 2014, 05:16 AM

QUOTE (marsophile @ Jun 29 2014, 09:02 PM) *
perhaps one should be wary about drawing conclusions from a calculation...

With all due respect to the modeling, I'd only draw conclusions from properly-calibrated images, which I've seen none of in this thread (maybe the Viking images, though Viking calibration is somewhat problematic.) The coverage of the sky at different elevations has been very limited from MSL so far, though there was one zenith image taken with MAHLI if I recall correctly.

Of course, considering the title of this thread, the whole discussion of sky color is wildly off-topic.

Posted by: serpens Jun 30 2014, 05:49 AM

QUOTE (mcaplinger @ Jun 30 2014, 06:16 AM) *
Of course, considering the title of this thread, the whole discussion of sky color is wildly off-topic.


Amen to that

Posted by: vikingmars Jun 30 2014, 02:49 PM

QUOTE (David Palmer @ Jun 27 2014, 11:35 AM) *
reply to vikingmars ("About the color of the Martian sky"):

Thank you Dave for your kind comments.
The link you are referring to are the images processed in 1990 by Mary-Ann Dale-Bannister (Washington University, St. Louis) who, successfully was the first to try combining high-resolution black-and-white images (BB3 and BB4 diodes) with the 3 lower-resolution channels (RED, GRN and BLU) images from the Viking Landers.
When the images were issued, we just stared at them, much amazed and impressed by their quality and their good definition.
BUT, the color balance was not done EXCEPT for the mosaic (link http://nssdc.gsfc.nasa.gov/photo_gallery/caption/vikinglander2-1.txt ) which shows colors close the real ones and that was the ony mosaic aknowledged to bear "Real Colors at VL-2" by Mary-Ann herself (but not for the other ones).
A good proof is that, within the same data set, are some other processings done by Mary-Ann in which you can found one which is close to my mosaic BUT which does not reflect the real colors unfortunately (see herebelow). Her goal was to give a lecture about the effects of winds on Mars but NOT about the colors of Mars...

And, I must agree with you on this specific point, it is true that, under very, very low atmospheric opacities, the Martian sky tends to turn a "grayish-pink" 30° above the horizon smile.gif
<== (Mary-Ann processing done here only to show the low sky luminosity under a dust storm, NOT for the real colors)

Posted by: Astro0 Jun 30 2014, 10:56 PM

ADMIN NOTE: All, as noted a few posts earlier, let's keep this discussion ON TOPIC. We're going over OLD ground or sky in this instance. wink.gif

Posted by: serpens Jul 1 2014, 06:09 AM

The more I look at the "headwaters" of the Mount Sharp channels the more it appears that the channels have been covered by the aeolian deposits that characterise the upper region of the mountain, rather than originating there. The inference is that the channels date from the early period where the crater was infilling and it is only recently (in martian terms) that the less consolidated material has been eroded away to reveal the lithified channels and deltas. An indication of the topography that would enable such channel formation is provided by Endeavour crater which has been overrun by sediment from the NW. If there was surface water flowing in Meridiani today it would possibly flow into the crater, cutting channels in the mound slope similar to those on Mount Sharp, terminating in a lake. Aeolian mountain building process and erosion like those proposed for Gale would then result in topography similar to the Gale channels/deltas, albeit on a much smaller scale.

 

Posted by: David Palmer Jul 1 2014, 09:10 AM

Reply to Serpens:

Your hypothesis (which we can christen the "overland-flow hypothesis") is not plausible, for several reasons:

1) To have such an overland flow which then poured down the northern and western sides of what was to become Mt. Sharp (carving the channels in the process), the eastern/southern portions of Gale Crater would have needed to be filled with sediments to the brim, forming a tableland....but if that were the case, why would the northern/western area of Gale Crater have been sediment-free? (which would have been needed to provide a basin into which the channels dumped their load).

2) Looking at the headwater of the Grand Canyon (seen in the image you pasted above), it is obvious that the channel is beginning at this point, as a juvenile channel that is both shallow and narrow, whereas if the (visible) Grand Canyon were a surviving remnant of what was originally a channel sourced from a great distance, flowing across a tableland (which has since eroded away), then it would have acquired the traits of a mature channel (full or near-full width and depth) LONG before the location of the Grand Canyon's visible headwater.

3) It HAS been suggested by other authors, possibly first by Anderson & Bell, that the Upper Formation was laid down on top of the lower mound AFTER the channels were carved. And this would indeed provide a possible mechanism for protecting the channels and their deltas from erosion and meteor impacts, until such time as these (presumably friable) sediments were stripped away via wind erosion. However, this is not plausible.....the surviving Upper Formation is at least reasonably lithified, as demonstrated by the crisp surface features visible in high-resolution photos of the mountain, including yardangs, ridges, steep topographic gradients such as scarps and cliff-bench layering, impact craters, and boulders in colluvium piles, all of which imply a hardened, indurated substrate (i.e., rock).

If an underlying formation is covered by a later formation that is lithified to a comparable degree (one that is NOT friable and unconsolidated), then the stripping away of the overlying formation can be expected to inflict heavy damage to the lower (older) formation, as there would be no clear dividing line between the formations that would result in highly differential erosion. And if this had happened to the Mt. Sharp channel complex and fans, they would today be a mess, with some portions still obscured by their original sedimentary cover, other portions filled in or covered up by newer (reworked) materials, and still other portions gone forever as a result of erosional cross-cutting or systematic deflation of the landscape, in short a geologic hodge-podge that would require detailed stratigraphic research in order to decipher the original structure (if it even could be deciphered), rather than the channel complex being showcased before us in gleaming, near-mint condition (as it obviously is). And to suggest otherwise would actually involve a violation of the Second Law of Thermodynamics, since erosion is a very highly entropy-producing process, and cannot be expected to cleanly pluck away an overlying formation, almost grain by grain (as if by the Hand of God), without also doing great damage to the underlying formation.

And there is no conceivable mechanism whereby the material that today constitutes the upper mound was lithified, but the outlying materials of the same formation were not (and so could be readily stripped away without substantially damaging the channel complex)....unless, of course, an artesian hydrant were present (as per my essay's main hypothesis) that would provide lithifying water exclusively to the sediments sitting on top of Mt. Sharp (i.e. the upper mound), in which case we also have a ready source for the water carving the channels, and the overland-flow hypothesis becomes redundant.

Dave

Posted by: Gerald Jul 1 2014, 12:26 PM

QUOTE (David Palmer @ Jul 1 2014, 11:10 AM) *
And there is no conceivable mechanism whereby the material that today constitutes the upper mound was lithified, but the outlying materials of the same formation were not ...

I admit, that I didn't (yet) read all of your essay. But did you consider an ice cap or permafrost as a possible protective mechanism? This works at least for mountains on Earth. Lower parts tend to melt earlier, hence loose their protective property earlier, and are eroded faster. An ice cap could also explain the canyons, as e.g. fjords in polar regions on Earth.
Then add the - currently I think mainstream - http://www.gps.caltech.edu/~kite/doc/Kite_et_al_Gale_Mound.pdf, which are stronger at the base of the mount, and accelerate erosion further.
The central mount has been higher, even after sedimentation due to the initial impact, this way starting the preferred erosion in the "low-lands".

I don't claim this as the only possible explanation, but just to given an idea that there may be plenty of alternative conceivable mechanisms.

Usually I avoid to discuss about the overall geomorpholgy of Gale, since I think finding "the" correct hypotheses without a huge amount of data and their deep analysis is like a lottery with a couple of tries within millions of possibilities, just think about the largely unknown climate on past Mars, e.g. due to the http://hirise.lpl.arizona.edu/ESP_034132_1750, add volcanism and large impacts. You might win the super-jackpot, but a-priori-chances are low.


About the artesian spring hypothesis: Shouldn't there be obvious http://en.wikipedia.org/wiki/Cenote like in the http://en.wikipedia.org/wiki/Chicxulub_crater region, due to leaching? And: How did the water manage to get out only at the mount, not at fractures somewhere else (think about the hydrostatic pressure), leaving several smaller mounts in the surroundings?

Posted by: serpens Jul 1 2014, 02:56 PM

I have a little difficulty with some of the assumptions on which you base your last post David. Taking your numbered points:

(1) Endeavour crater currently reflects the required topography so it is possible that so could Gale at the time the channels were formed.

(2) To my eyes the channel is not pristine and the filled remnant wends towards the top right of the image, disappearing under the (Aeolian?) sediment without narrowing.

(3) The extent of lithification of the various levels of mount Sharp can only be assessed if Curiosity gets up close and personal. But I submit that can assume that the lower (dark) beds will have been saturated (Curiosity's findings, the presence of boxwork and clays and the channels/delta deposits). The overlaying light (Aeolian) deposits evident in the layers above this level would almost certainly have much reduced cementation. So there would seem to be a reasonable probability of a significant difference in erosional vulnerability, particularly in light of the increasingly gentle environment of the past few billion years.

Painstaking analysis of Curiosity's findings by the resident experts will narrow the field but as I mentioned previously, there will probably be a number of hypotheses as to the formation of Gale alive and well at the end of the mission. Consider how long it took to get a handle on Opportunity's small area of Meridiani. Anyway, as you are aware I threw the "overland-flow hypothesis" as you termed it in purely to point out that there are alternatives to an extremely high pressure aquifer to explain the Mount Sharp channel features. But it is merely wild arm waving from the depth of an armchair and not worth argument.

Posted by: David Palmer Jul 1 2014, 09:33 PM

Reply to Serpens:

Actually, I WANT "argumentation" over my hypotheses....my model needs to be roundly criticized, it needs to go through the wringer....its not just there to sit and look pretty.....and I figure that by this time next year, it will have been proven right or wrong. It's put forth as a serious scientific hypothesis, which means it is something that needs to be tested....Emily (elakdawalla) doesn't seem to understand exactly what I am trying to accomplish here....just because I am an amateur scientist, and this is a hobby of mine, doesn't mean I also can't be attempting serious science, and attempting to get the notice of professional planetary scientists. And sure, I'm going out on a limb by presenting my ideas, but there's a void to be filled, because no one else has a coherent, all-encompassing model to present. And although Gerald wishes to wait till there is more data in, I figure that the prize is to be had by the person who jumps into the fray and is the first to come up with a model that holds water (no pun intended), even before the so called "experts."

I'm having to get back to work now, but later today I'll make specific replies (concerning geology) to you and Gerald.

Dave

Posted by: ngunn Jul 1 2014, 10:09 PM

QUOTE (David Palmer @ Jul 1 2014, 10:33 PM) *
Reply to Serpens:

Actually, I WANT "argumentation" over my hypotheses.

just because I am an amateur scientist, and this is a hobby of mine, doesn't mean I also can't be attempting serious science,


This is indeed a place where engagement with non-professional contributions have resulted in fruitful discussions, and I hope that's what will happen here. To encourage that you need to bend a bit with incoming comment, accept that learning is a two-way process and so forth.

I'm an interested follower of the thread. I do think Aeolis Mons is bizarre and takes a bit of explaining.

Posted by: Gerald Jul 1 2014, 11:12 PM

QUOTE (David Palmer @ Jul 1 2014, 11:33 PM) *
...just because I am an amateur scientist, doesn't mean I also can't be attempting serious science, and attempting to get the notice of professional planetary scientists.

If you persue this idea seriously, I'd suggest first to duplicate Kite et al's simulations, as an exercise.
Then model your ideas, and run similar simulations. Compare the results of the simulations with each other, and with available data.
Describe your model and simulation runs in a way, that other scientists can duplicate your results, usually as a paper. Show, that the results of your model fit better to the empirical data than results of other models.

Posted by: David Palmer Jul 2 2014, 07:43 AM

Reply to Gerald:

It is beyond my means to do a computer simulation or mathematical modeling of SWEET, however that is not a requirement. If I can show that Kite's SWEET hypothesis is logically incoherent or in conflict with empirical data, that is all that's needed. And in fact, my essay was originally motivated by reading the SWEET hypothesis and finding it anything but "sweet."

In my essay, I point out MANY insoluble problems with SWEET, and here is an example: it proposes that wind-entrained sediment drops when it encounters the "stagnant air" in the center of Gale (building up a mound), however the Upper Formation consists of cross-bedded dune deposits, which require strong horizontal surface winds to form....and not only is this incompatible with SWEET's aeolian model, but it would cause the sediment to cascade down the side of Mt. Sharp, and the upper mound never be able to form (the only model that makes sense is that the entire crater was filled with extended horizontal sediments, and there was a dune field on top of those sediments).

As far as a mathematical modeling or simulation of my hypothesis, all that is needed is a determination that there is (or was) a net hydraulic head at the location I propose (6,000 feet below datum), and indeed this is/was the case, thanks to the low elevation of Gale, and the high surrounding terrain. And in fact, there probably still is, considering that there was an outflow at Cerberus Fossae (likely from the same aquifer) several million years ago that is estimated to have had a nearly 3-mile-high effective hydraulic head (according to James Head, et al....again, no pun intended). And if the Martian aquifer is still that active, it was certainly FAR more than adequate to fill Gale Crater in the distant past. Hence, bye-bye SWEET (although I do agree with a number of aspects of the wind regime they model, as I explain in my essay, and attribute the erosional deflation of the outlying parts of the crater fill of Gale to those winds).

Concerning your earlier posting: the channels of Mt. Sharp are NOT fjords, those are U-shaped glacial valleys that have moraines at their end, whereas the channels are obviously water-carved, and have deltas at their end. And because of the lack of available watershed area and the lack of a dendritic tributary system, the obvious interpretation is that they were spring-fed.

Also, an ice cover could not have protected the channels and deltas from wind erosion and meteor impacts, as conditions over the last few billion years have been generally far too dry to allow surface ice at this location (it's only been present during high obliquities).

Concerning your suggestion that there should be "cenotes" in Gale Crater if there was an aquifer like I am proposing: cenotes normally form in karst terrain with a limestone basement, where water flow through fractures widens those fractures further (due to the high solubility of carbonates), until sink holes or related features develop (and such a basement was present at Chicxulub). But with a basaltic basement, as in Gale, things are the opposite: the minerals in basalt are relatively insoluble, and in response to weathering in the presence of water, they swell to form clays and so will tend to fill fracures. PLUS, almost the entire region, especially the floor of Gale, is covered by fine-grained (frequently clay-rich) sediments, which are a very effective aquiclude, and would serve to contain an aquifer and allow it to build up high pressures.

My suggestion is that the only area in the local terrain that still has fractures commuting from the surface to the deep aquifer, and thus the only location where water could exit, would be the (largely buried) central peak and its associated megabreccia field (and in fact, as indicated by Schwenzer et al, on the east/southeast side of Mt. Sharp they do show spectroscopic clay signatures at approximately the same elevation as the headwaters of the channels on the west side of the mountain, suggesting seepage from fractures, and which provides additional support for my artesian hydrant hypothesis).

Dave

Posted by: Gerald Jul 2 2014, 12:12 PM

Picking out a couple of statements:

QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
It is beyond my means to do a computer simulation or mathematical modeling of SWEET, however that is not a requirement.

This would have been a way to become accepted by professionals.
QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
If I can show that Kite's SWEET hypothesis is logically incoherent

Computer simulations are a good way to reduce that risk drastically, since simulations use to refuse running, if inconsistent.
QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
...it proposes that wind-entrained sediment drops when it encounters the "stagnant air" in the center of Gale (building up a mound), however the Upper Formation consists of cross-bedded dune deposits, which require strong horizontal surface winds to form

A net deposition is sufficient for the growth of the mound, supported by humidity. Low humidity levels may be sufficient to form thin crusts supported by hygroscopic salts like almost ubiquitious http://onlinelibrary.wiley.com/doi/10.1029/2009JE003425/pdf. The crusts reduce erosion for settled strata, be it horizontally-layered or dune fields.


QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
the channels of Mt. Sharp are NOT fjords, those are U-shaped glacial valleys that have moraines at their end, whereas the channels are obviously water-carved, and have deltas at their end. And because of the lack of available watershed area and the lack of a dendritic tributary system, the obvious interpretation is that they were spring-fed.

Alternatively, melting ice caps washed away parts of the moraines and formed deltas, most remnants of the moraines wheathered physically and were transported away by slope winds, some remnants may still be there and accessible for investigation by MSL. No need for a tributary system, and if it has been present, most of it would have been eroded by now.
QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
Also, an ice cover could not have protected the channels and deltas from wind erosion and meteor impacts, as conditions over the last few billion years have been generally far too dry to allow surface ice at this location (it's only been present during high obliquities).

It could, since it allowed for cementation and lithification, reducing erosion in the dry phases, when not covered by softer layers.
QUOTE (David Palmer @ Jul 2 2014, 09:43 AM) *
cenotes normally form in karst terrain with a limestone basement, where water flow through fractures widens those fractures further (due to the high solubility of carbonates)...

They can also form in a calcium sulfate-rich settings (on Earth: http://www.researchgate.net/publication/259569515_Gypsum_karst_in_the_Olvera_area_(Cdiz_province_Andalusia_Spain), e.g. in gypsum Keuper (upper Triassic) regions); hydrated calcium sulfates have been found in relevant amounts at Gale.
After an impact the underground is heavily fractured, not just at the central peak (see e.g. p.7 of http://www.planetary.brown.edu/pdfs/3763.pdf).

(I probably won't continue the discussion, since my priorities are somewhere else, but I'll read possible replies.)

Posted by: David Palmer Jul 2 2014, 01:59 PM

Reply to Gerald (my comments are in upper case): Admin Edit: Upper case is considered 'shouting'. Please either use "quotes" or as has been done in this case, italicise comments.

G: A net deposition is sufficient for the growth of the mound, supported by humidity. Low humidity levels may be sufficient to form thin crusts supported by hygroscopic salts like almost ubiquitious perchlorates. The crusts reduce erosion for settled strata, be it horizontally-layered or dune fields.

My point was that dunes shouldn't have even formed on Mt. Sharp, given the SWEET hypothesis.....because there shouldn't have been horizontal winds, and dunes only form on a near-horizontal surface, not the top of a mountain.

G: Alternatively, melting ice caps washed away parts of the moraines and formed deltas, most remnants of the moraines weathered physically and were transported away by slope winds, some remnants may still be there and accessible for investigation by MSL. No need for a tributary system, and if it has been present, most of it would have been eroded by now.

For such a small watershed, the flow rate produced by ice melt in such a cold environment would have been insufficient to transport the up-to-ten-meter-wide boulders we see in the channel fill.

[i]G: It (ice cover) could (have protected the channels), since it allowed for cementation and lithification, reducing erosion in the dry phases, when not covered by softer layers.

Lithification would not have protected the surface against meteor impacts, which are almost absent in the foothills of Mt. Sharp.

G:
(Cenotes) can also form in a calcium sulfate-rich settings (on Earth: e.g. in gypsum Keuper (upper Triassic) regions); hydrated calcium sulfates have been found in relevant amounts at Gale. After an impact the underground is heavily fractured, not just at the central peak

But the basement under the calcium-sulphate-containing surface sediments is what is important here, that is what lies between the surface layers and the aquifer....and on Mars it is almost always basalt...and in the floor of Gale Crater, there would have been an impact melt lake, which then cooled and solidified and formed cracks, but sedimentary deposition of fine-grained clay-rich materials in such a sump, together with authigenic clay production, could be expected to fill those cracks and form an aquiclude in the crater floor (forcing the water to exit the only fractures left open for it, even though that represents a higher elevation).

Posted by: serpens Jul 2 2014, 02:52 PM

ngunn provides some sage advice above. I commend it to both of you.

Kite's model is reasonably simple, but he clearly states that it was designed that way to investigate a concept. Shortcomings include assuming a non erodible crater floor, failing to consider the effect of a previous lacustrine environment and the overlooking the potential effects of valley exit winds or possible adiabatic warming of katabatic wind that on exit would end up warmer and less dense than the air at the crater floor, providing lift to aid central deposition. We also do not have a clue about the air density during the formation period. But I would assume that a degree of sensitivity analysis was employed and the model certainly fulfilled its intended purpose. While Dave presents a number of arguments against the concept these are based on assumptions and unsubstantiated statements, depending on qualitative reasoning (I think this therefore it is so).

Personally I don't see that concepts such as Aeolian slope wind formation, crater infill, "overland-flow", airfall (volcanic ash draping), surge deposits and springs are in any way mutually exclusive . It would seem that the lower dark beds of Gale were laid down in a neutral pH saturated environment where probably Mount Sharp merely consisted of a central uplift. Above that is a sulphate/clay mix which could imply an interface between basalt buffered ground /lake water and acidic inflow with the sulphates domination with height. The amount of material would seem to point to infill. If Curiosity makes it to the delta above the entry point then the pH of the deposit may provide an indication as to whether it came from a nearby basalt buffered ground water spring or whether it was acidic surface flow.

The higher reaches of Mount Sharp seem to have both massive layers and also cross beds with indications of deposition/erosion cycles and a number of deposition events with various material. My take for what it is worth is that Mount Sharp was formed through a combination of mechanisms over a long time. Mount Sharp is not so much an enigma as a jigsaw puzzle.

All possibilities remain in play. Edit. Inflow requires a transportation medium. Aeolian transportation results in cross beds. There are also massive beds in the upper level where air fall deposition is the most likely cause. The reduced impact evidence in the foothills would seem pretty compelling evidence to me that the area was buried and then exhumed.

Posted by: mcaplinger Jul 2 2014, 03:13 PM

QUOTE (David Palmer @ Jul 1 2014, 02:33 PM) *
...I figure that by this time next year, it will have been proven right or wrong... the prize is to be had by the person who jumps into the fray and is the first to come up with a model that holds water (no pun intended), even before the so called "experts."

What is the test for your hypothesis that you expect to be resolved in a year?

BTW, referring to the scientific community as "so-called experts" is a sure way to have your work dismissed.

Posted by: David Palmer Jul 2 2014, 03:29 PM

QUOTE (mcaplinger @ Jul 2 2014, 07:13 AM) *
What is the test for your hypothesis that you expect to be resolved in a year?


1. Particle size distribution, minerology, and bedding characteristics of the Lower Formation should all indicate lacustrine, not aeolian, deposition,
2. The channel fill of what I am referring to as the "Northern Channel" should show a very young cosmic-ray exposure age (several million years),
3. The minerology and isotopic ratios of the channel fill should reflect a groundwater origin, rather than surface precipitation (I am expecting a high salt content....and a bias towards heavy isotopes in the bound water, as compared with atmospheric moisture or frost or snow).

Posted by: Gerald Jul 2 2014, 05:30 PM

QUOTE (David Palmer @ Jul 2 2014, 05:29 PM) *
3. ...I am expecting a a bias towards heavy isotopes in the bound water...

Didn't you actually mean a bias towards light isotopes? That's what I would expect for an old aquifier.

Item 1 could be explained by lakes, ruling out Kite's simplified purely aeolean model, although not the concept;
item 2 could have been caused by rapid recent erosion.
Item 3 appears to be more specific to your main hypothesis of an ancient aquifier, although there may be some ambiguity with a hypothesis of an early formation of the channel filling material, or just old buried ice as kind of a local aquifier.

In which way is the test specific to the (high-pressure) artesian spring hypothesis? Or which additional tests could provide unambiguous evidence?

Posted by: serpens Jul 2 2014, 11:17 PM

A slight aside. I wonder at the validity of using high obliquity ice events to explain the channels and other features. Taking an extreme case of say 80% obliquity, Gale being equatorial will still have the sun directly overhead twice a year, and each pole will receive maximum insolation once a year when the other pole is dark as the tropic are positioned close to the poles. There would be transfer of significant amounts of CO2 and some entrained water vapour between poles and some increase in air pressure during transfer as is evidenced in the current environment. But how great a rise at the equator and how much ice could reasonably be expected to deposit, albeit for a short term is uncertain although there would probably be increased Aeolian activity. I expect that there are probably a number of models relating to this, but models of Earths climate are somewhat unreliable despite the wealth of empirical data available so perhaps models of Martian climate should be treated as indicative, not absolute. The point I am trying to make is that I really do not think that glacial activity, or even significant deposition of ice would feature at Gale, regardless of changing obliquity although early on when Mars had a denser atmosphere, high obliquitys would have been extremely energetic periods.

Posted by: Gerald Jul 3 2014, 12:20 AM

That's why I would prefer to wait for more reliable data. There are hypotheses ranging from a mild wet early Mars to Kite's snowball. May be both is true in hundreds of millions of years. A one degree change of obliquity on Earth is thought to cause ice ages. What would happen on a 10 degree change? A larger ice shield at the poles may lead to a run-away cooling due to higher albedo. We don't know whether there have been oceans on Mars, and if so, when, and to what extend? What's the consequence for the humidity of the atmosphere, and the amount of snowfall? That's simply too complicated to estimate, at least for me. I'd think, that climate changes on Mars have been much more severe, and more frequent than on Earth, and Mars should be cooler than Earth on average due to the larger distance from the Sun. But if there had been much CO2 or even CH4 in the Martian atmosphere, there might have been a strong greenhouse effect. On the other hand, SO2 resp. elementary sulfur in the atmosphere (due to volcanism) would probably lead to additional cooling.
We also don't know the vertical temperature profile of early Mars. High mountains, like e.g. http://www.peakbagger.com/photo.ashx?phid=425&l=1 (Kilimanjaro) on Earth (still) have an ice cap despite their proximity to the equator. Without additional information, I'd apply this observation also to early Mars, and consider the fainter Sun.
With all these uncertainties I can't at least rule out temporary ice caps on Mt Sharp as a valid hypothesis, on the current thin basis of knowledge.

Posted by: David Palmer Jul 3 2014, 02:48 AM

Reply to Gerald:

No, I did mean what I said, that groundwater would be enriched in heavy hydrogen and oxygen isotopes, relative to atmospheric precipitation (and thus any residual bound water in minerals and sediments that interacted with this ground water, such as ones eroded and transported by spring water, would show such an enrichment).

Any atmospheric precipitation will be biased towards light isotopes, because lighter molecules are slightly more apt to evaporate. This effect becomes significant in some environments on Earth....in the polar regions, deuterium concentrations in snow can be 40% lower than in sea water. And the same is true for groundwater vs. atmospheric moisture....groundwater will have a relative over-abundance of heavy isotopes, compared with water that has evaporated and subsequently precipitated.

For example, see http://www.whoi.edu/cms/files/kcasciotti/2006/9/Gat1996_14124.pdf

You are quite right in saying that a lacustrine origin for the Lower Formation would not prove my hypothesis....but it is a necessary condition for that hypothesis to be valid (a necessary but not sufficient condition, to use terminology from logic).

The first condition lays the groundwork for the possibility of my hypothesis being right, but the later two conditions are more directly a test of it (low cosmic ray exposure age, and chemistry and isotopic ratios characteristic of groundwater involvement).

You state that a low cosmic ray exposure age could also be the result of rapid erosion (of very ancient materials), and not signify recent deposition. However, my point is that IF rapid erosion of a relatively thin formation is occurring (several hundred feet thick, in the case of the channel fill), that observation suggests that the strata in question is fairly young (I am claiming less that 100 million years old), because given such a rapid erosion rate, any such thin (surface) deposit would otherwise be long gone. The only alternative would be that a (now vanished) overlying stratum was protecting the channel fill until recent geologic times, but this would seem an unlikely coincidence, especially considering that (per the law of superposition) the channel fill is one of the most recent deposits in the Gale/Mt. Sharp complex (it overlies the mound-skirting unit, which in turn embays the Peace Vallis fan deposits).

So it can be seen that my "artesian hydrant" hypothesis is a scientific hypothesis in the truest sense of the word, with very specific, quantitative, field-testable predictions (another of which, unfortunately, may have to wait till the distant future to be tested....namely my prediction that there will be underground conduits in Mt. Sharp, to be mapped out by high-definition ground-penetrating radar or seismic studies).

Dave

Posted by: David Palmer Jul 3 2014, 03:36 AM

Reply to dialogue between Serpens and Gerald:

I don't agree with Kite's model for the origin of the Mt. Sharp sedimentary column, however I do recognize his contribution to climatic modeling for Mars, such as in: ”Seasonal melting and the formation of sedimentary rocks on Mars, with predictions for the Gale Crater mound.” ¯ Icarus 223 (2013) 181-210.
http://gps.caltech.edu/~kite/doc/seasonal_melting_and_sedimentary_rocks.pdf

In that article, he presents the results of models that suggest that Gale would be one of the most likely places on Mars to experience liquid water flow, as a result of obliquity-driven precipitation and subsequent ice/snow melt. And I figure that the proof is in the pudding: the entire Gale/Mt. Sharp complex (the mountain, the crater floor, and the crater rim) shows unmistakable signs of repeated aqueous events (as well as glacial and periglacial activity) over a very long time, and the natural interpretation is that these events were obliquity-driven, although volcanism also would be expected to play a major role (during periods of intense volcanism, much carbon dioxide and water vapor would be injected into the atmosphere, and high obliquities correlated with volcanic activity should result in an especially favorable mileau for Gale Crater).

I also agree with much of Kite's aeolian model for Gale Crater (I attribute the deflation of the outer portions of the crater fill to such a wind regime).....where I break with him, is in the temporal assignation of the climactic regimes he defines: his description is probably a good one for the latter half of the Hesparian and for the entirety of the Amazonian, but the early history of Gale (and of Mars in general) was FAR wetter than his model suggests (and that's the environment in which the majority of the Mt. Sharp sedimentary column was laid down).

Dave

Posted by: serpens Jul 3 2014, 05:09 AM

Apply Kite's model to the massive, upper stage of Mount Sharps formation and it fits very well indeed. It would probably be best if you couched your statements as beliefs as opposed to facts. For example you may believe that "the entire Gale/Mt. Sharp complex (the mountain, the crater floor, and the crater rim) shows unmistakable signs of repeated aqueous events (as well as glacial and periglacial activity) over a very long time". There is no wide agreement on that, nor definitive evidence, so the statement is your interpretation, not a fact. You have a deep belief in your high pressure aquifer release hypothesis as the cause of the channels but again, that is a personal belief rather than a fact. If you want to explain Gale topography as the product of a wide area, high pressure aquifer then you need to marshal some defensible arguments in the context of the region. Try considering the possibility that the volcanic activity /uplift involved an ambulatory process and think about the flooding effect and ocean rise if the volcanic activity was coincident with an existing ocean. Pointing to Cerberus Fossae and saying here be the aquifer is drawing an exceedingly long bow. Explain why the release occurred in the central mountain and not the equally fractured crater walls or the low terrain to the North.

Posted by: David Palmer Jul 3 2014, 12:11 PM

Reply to Serpens:

There is quite a lot of ground to cover here.

I disagree with your interpretation of the headwater of the Grand Canyon....you state that it doesn't narrow prior to disappearing at the bottom edge of the Upper Formation (the implication being that if it were not in unconformable relation with the Upper Formation and buried by that formation, it should pinch out to a narrow gully prior to disappearing)....but I believe that the reason for this is that the visible channel never was the conduit for water that proceeded to flow down the Grand Canyon. Such a conclusion is suggested by the fact that this "headwater channel" is too small a channel (it has too small a cross-sectional area) to have contained the huge flow required to cut the Grand Canyon, move ten-meter-wide boulders, and deposit the delta at the terminus of that canyon (both its width and depth are a small fraction of the dimensions of the lower canyon). We observe that the channel suddenly changes to a canyon at approximately the 7-mile mark, and this canyon proceeds to widen and deepen as we move downstream, but WITHOUT tributaries that could explain the corresponding flow increase and erosive capability.

I would suggest the following as an explanation for this apparent paradox (that the channel had a high flow rate without a headwater or tributaries to support it): although there may have been some flow in the visible headwater channel, what we are interpreting as a channel is primarily a subsidence feature on top of a largely hollowed-out subsurface (which is where most of the flow took place). This is a pattern we see fairly often in Earthly settings, where there is a sudden transition from shallow to deep runoff channel, involving flow through fissures or porosity of the rock beneath what we see as the visible channel, until the bulk of that flow transitions to being surface flow, from springs and general seepage. And I would suggest that we are seeing the first of these (dormant) springs where the channel suddenly deepens (at the 7-mile mark), and that there were additional springs in the canyon floor and walls, augmenting the total flow, as we moved downhill.

Support for this model is provided by the occurrence of numerous box canyons in the western lobe of Mt. Sharp, apparently brought about by groundwater sapping from springs, with stubby heads that have been eroded backwards into the mountain (but with no signs of being fed by surface flow), and with termini featuring debris lobes. The "Grand Canyon" simply happens to be the largest of these, and it appears that Mt. Sharp is highly fractured, featuring dormant springs that can become active again under the proper conditions.

The fact that the headwater channel doesn't narrow prior to disappearing into the hill, is consistent with the channel being a collapse zone, wherein the rise in the lay of the land as we move further east, eventually creates enough of a roof arch above the subsurface flow to prevent subsidence.

As I have previously stated, if the Grand Canyon were the product of overland flow from a substantial distance (across a hypothetical tableland in the eastern portion of Gale), then it would be a deep, wide, mature channel by the time that reached the spot where we see the "headwater" channel, and the Grand Canyon would not be expected to begin with such morphology.

Also I find the concept of a tableland in the eastern portion of Gale to be suspect, as there is no obvious way to account for its subsequent erosion, while at the same time the western face of Mt. Sharp remained comparatively unmolested (such that channels and thin delta deposits survived subsequent geologic history).

I do not believe that SWEET is able to account for the Upper Formation, the most serious flaw being the extensive cross-bedding (see photo), which could not be the result of the predicted winds, but only of horizontal winds, and in any case, a dune field could not be expected to form on top of a mountain, and if it managed to, said horizontal winds would quickly send it packing downslope.



I do not consider Cerberus Fossae irrelevant for understanding Gale. Those outflows show that Mars still has an active aquifer that is under pressure (and one which is capable of reaching the surface), and there is no reason to believe there is any relevant subsurface barrier across the Elysium plains between the two locales, so they should in fact share the same aquifer.

To see how water has repeatedly left its mark on the Gale/Mt. Sharp complex, all that is needed is to look at photos of the crater floor (showing multiple generations of fans and channels stacked on top of each other) and photos of the crater rim, showing numerous stream-carved valleys and canyons that were obviously not created by some huge catastrophic Noah-type flood, but over an extended time from innumerable individual events, likely in association with obliquity changes and also volcanic and possibly asteroid-collision events, with the net result being a landscape that looks very much like the Southwest desert terrain of the US (which has also been subject to periodic fluvial events). This is not just an opinion on my part.

I consider it highly unlikely that the foothills of Mt. Sharp (and the channels) have had a protective aeolian cover on them that has recently been stripped away, because of the immense damage that such a stripping action would also have delivered to the underlying surface, given that an extension of the Upper Formation would likely require violent stripping action to remove, considering how well-lithified the Upper Formation appears to be.....likely to a comparable degree as the Lower Formation (the implication being that the surface on the lower flank of Mt. Sharp is young, with the channels most recently active several tens of millions of years ago). You stated that we can't really tell the relative state of lithification until Curiosity reaches the deposits, but unfortunately Curiosity will never be able to drive up to the Upper Formation, so we have to make do with HiRISE imagery, which indicates that the Upper Formation is fairly erosion-resistant. And if indeed it is an outlier of the Medusa Fossae formation, as seems likely, the upper mound must be well-lithified indeed, to have survived an erosional environment that has removed all other local exposures of that formation, including at lower levels....and that fact fits very well within my artesian hydrant model, in that water would have been available to provide a degree of lithification that was highly atypical for the Medusa Fossae.

You stated that it is implausible that aquifer outflows would occur in Mt. Sharp but not in the "equally fractured" crater wall, or in the low terrain to the north. I would suggest that aquicludes play the same role in the Northern Plains as they do in the floor of Gale. And as regards the crater rim/wall, I don't see any reason to think that fractures would be deep enough at those locations to reach the aquifer, which would be separated from the surface by at least a mile of basalt and a very solid cryosphere (whereas the fractures would be expected to reach very deeply indeed under the center of the crater). Although I can't vouch for its detailed accuracy, the included figure (courtesy of NASA) shows how there would be deep fractures beneath Gale, but not necessarily in the crater rim/wall.



The reason that I robustly support my Artesian Hydrant hypothesis, is that it seems to account for all empirical observations of the Gale/Mt. Sharp complex, and is also internally coherent logically, whereas there are serious difficulties with all other models I have seen, either in terms of their basic theory or in terms of meshing with the data.

Dave

Posted by: Astro0 Jul 3 2014, 01:31 PM

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