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Thread: Martian Ice Structures

  1. #1
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    Martian Ice Structures

    this is a NASA image, so I think there is no copyright issue, if so please remove the image tags

    I really find this image of the Northern Ice Cap on Mars appealing. There is so much going on there. First the spiral troughs give a huge pinwheel impression. Second Chasma Boreale dominates the image like a huge mouth on a person. I am fascinated by both and have my own ideas on what caused them, but I'd like to know what others think. Also, I'd like to know about how old they are. One of the big questions regarding the spiral troughs and Chasma Boreale is if they are younger than the caps and were cut into the ice cap, or if they are old and grew with the ice.

    The Southern Ice Cap has similar structures, but they are opposite in direction.

    (I believe this also to be public domain)


    The southern ice cap is actually much, much larger than what we see here. What we're looking at is the CO2 ice remaining in the warmer months. The water-ice is darker due to a large dust content.



    So, I'm working on an idea as to why they are spiraled. And I have done work on how old they are.

    What do y'all think about the age and generation of these features?
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  2. #2
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    There is no visible cratering so relatively young. Are you sure it is the ice that is spiralling and not the overlying aeolian dust?

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    Quote Originally Posted by crosscountry View Post
    I have done work on how old they are.
    Specifically, by what process were you able to determine "how old they are"?
    The facts, gentlemen, and nothing but the facts, for careful eyes are narrowly watching. Isaac Asimov

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    I use ice penetrating radar to see the stratigraphic record. The troughs are recorded in that stratigraphy well below the current surface. Age in this case is a relative term as in "older" and "younger". But I'd like to get something more exacting.
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    I always assumed the shape was due to prevailing winds and patterns of dust blown onto the ice.

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    Neglect not:

    Space.com: Mars Mystery: Strange Spirals in Ice Caps Explained

    It's no accident that the Martian spirals take on a familiar look.

    Their ever-expanding arms follow a pattern known as a logarithmic spiral, arms tight at the center and growing rapidly farther apart as they splay out. It is a common pattern in nature, repeated in hurricanes (when viewed from above), the seashells of the chambered nautilus, and even in the descending flight pattern of a bird of prey.

    "The logarithmic pattern occurs because the troughs migrate at a slower rate near the poles because it is colder there and melting takes place more slowly," Pelletier said. "This causes them to 'bunch up' nearer towards the poles."
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

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    Quote Originally Posted by 01101001 View Post
    nice find. I have read his paper and found it interesting. There are a handful of alternative ideas that are at first glance equally viable. But my research shows that most of them cannot be true.

    Alan Howard wrote a paper in 2000 citing all the evidence for wind driven trough migration, and it's a thick paper. He and a few others, including Steven Squyres notably, predicted that the troughs would migrate due to ablation (as noted in the link you provide) and also due to spiraling winds coming from the north pole. The winds spiral similar to a Hurricane except in reverse because they are high pressure fronts rather than low pressure. It is tricky to visualize, but the wind pattern is perpendicular to the pattern of the troughs. See Howard 2000 for a map.

    My research shows that both causes are happening or have happened in the past. What I'm still missing is the cause of initiation of the troughs, and while Pelletier's ideas sound plausible they do no manifest in the data.
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    Estimates of the age of the N polar cap's surface are ~10-100 kyr (Banks, M.E. et al. (2009). "Crater Population and Resurfacing of the Martian North Polar Cap" LPSC XL Abstracts, and references therein). Chasma Boreale doesn't have a well-constrained crater age at least from my database, and I don't know of papers off-hand that date its surface.

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    Geography from a distance has its drawbacks. Send the space craft. load it up with all sorts of robotics.. all we need is a huge pile of money or a sponsor...
    I find the explanations thus far are interesting if not actually the whole answer. Have any of you noticed how quick we are to prejudge the unknown on what seems like half the information required. Its not very scientific is it ? yet it seems to happen a lot round here.

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    Quote Originally Posted by astromark View Post
    Geography from a distance has its drawbacks. Send the space craft. load it up with all sorts of robotics.. all we need is a huge pile of money or a sponsor...
    I find the explanations thus far are interesting if not actually the whole answer. Have any of you noticed how quick we are to prejudge the unknown on what seems like half the information required. Its not very scientific is it ? yet it seems to happen a lot round here.
    To what above reply are you commenting on?

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    Quote.. "To what above reply are you commenting on?"...

    Stu ;I have read all of the contrabutions thus far in this thread. Some of the work and research is impressive is it not ? I think my post #9 says exactly what I wanted it to.. I find the tendency of us to draw conclusions of fact from half of them, amusing.... I am not being drawn into some foolish personal mud fight. I do not have the facts before me to be absolutely sure of this ice formations and pattern. It would seem the information required to answer this absolutely is not yet in. Its impressive that we can know so much from so far... That is all I am saying. Do not read into my post what is not there.

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    Mark - I didn't intend to draw you into a mud-slinging (ice-slinging?) contest, it's late here so perhaps I implied a tone I did not mean. I was more interested as to whether you were addressing my reply, specifically, in which case I could post more detailed information on the theory and ground-truthing of crater-age dating, which is what I happen to do, and it's a pretty well understood process. But, if you were aimed more towards someone else's response, then I wasn't going to be able to back it up, such as the theory in regards to why there are the spiral growth patterns.

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    Quote Originally Posted by stu View Post
    Estimates of the age of the N polar cap's surface are ~10-100 kyr (Banks, M.E. et al. (2009). "Crater Population and Resurfacing of the Martian North Polar Cap" LPSC XL Abstracts, and references therein). Chasma Boreale doesn't have a well-constrained crater age at least from my database, and I don't know of papers off-hand that date its surface.
    Yea, that's the surface, and I think people lean more towards the 100ky age. The drawback is that this only dates the surface. The NP Cap is approximately 2km thick and contains many layers, each of which may be 100k years.

    That is an interesting take though. Maybe I can use the surface to estimate each layer - but that's not very rigorous.
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    Revival for another analysis, components of which are mentioned above.

    NASA MRO News Release: NASA Spacecraft Penetrates Mysteries Of Martian Ice Cap

    Data from Mars now points to both the canyon and spiral troughs being created and shaped primarily by wind. Rather than being cut into existing ice very recently, the features formed over millions of years as the ice sheet grew. By influencing wind patterns, the shape of underlying, older ice controlled where and how the features grew.

    "Nobody realized that there would be such complex structures in the layers," said Jack Holt, of the University of Texas at Austin's Institute for Geophysics. Holt is the lead author of the paper focusing on Chasma Boreale. "The layers record a history of ice accumulation, erosion and wind transport. From that, we can recover a history of climate that's much more detailed than anybody expected."
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    Skepticism enables us to distinguish fancy from fact, to test our speculations. --Carl Sagan

  15. #15
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    and it was on Universe Today where my name is mentioned (Isaac Smith). Jack Holt wrote the Chasma Boreale paper and second authored the trough paper.


    The question last year was because the wind blown bedform idea was technically ATM at the time, and I wasn't sure the current belief was.
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    I see your article mentions the katabatic winds.

    I was going to ask about that, having been familiarized with them through studying the ecosystem of "Beringia" during the glaciations. When the Russian ice sheet was in place, the winds coming off it kept the Texas sized land bridge between Russia and Alaska free of permenent ice and snow even in the winter.

    This allowed herbivores, most of whom can survive on dry grass as long as it's not buried and they can reach it, to migrate freely back and forth. And strong evidence suggests lions actually evolved there. From bone analysis as specialized "bovivores".
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    Quote Originally Posted by BigDon View Post
    I see your article mentions the katabatic winds.

    I was going to ask about that, having been familiarized with them through studying the ecosystem of "Beringia" during the glaciations. When the Russian ice sheet was in place, the winds coming off it kept the Texas sized land bridge between Russia and Alaska free of permenent ice and snow even in the winter.

    This allowed herbivores, most of whom can survive on dry grass as long as it's not buried and they can reach it, to migrate freely back and forth. And strong evidence suggests lions actually evolved there. From bone analysis as specialized "bovivores".
    that wouldn't explain our lack of big lions here in North America. We do have cats, but they are more removed from those of Asia that an ancestor that recent would suggest. Or maybe I'm off base.
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