Planet Four Talk

Day and Night - Yardangs?

  • JellyMonster by JellyMonster

    I'm assuming that the darker part of the image is a very large fan or blotch? Reminds me of Escher's Day and Night drawing.

    UPDATE: It seems that it is a multitude of fans over a large area, see APF0001epp.

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  • Kitharode by Kitharode moderator

    It looks like yardang territory to me. I'm assuming ice cover forming 'polygons' giving linear venting.

    In your update image (apf 0001epp) I see those 'hair lines' we've discussed before forming a 'net' over the yardangs. It looks to me as if the venting follows the hair lines in that image.

    Escher - didn't know whether he was coming or going. ** 😛 **

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  • JellyMonster by JellyMonster

    I'm struggling to see the hairlines 😦.

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  • Kitharode by Kitharode moderator

    In your update image. General background is pale tramlines top left to bottom right. Middle of image taken up by black 'rectangle' sharply defined on right hand edge by a hair line. I'd guess the line progresses upwards and forms the front edge of the broken line of venting.

    The left hand edge of the rectangle is also defined by a thin white hair line which continues upwards from the top left corner of the rectangle. This line also appears to be a front edge for linear venting, some of which is overlaying existing dust.

    Basically, the thin white lines that meander around and across the tramlines are what I'm calling hair lines.

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  • wassock by wassock moderator

    Best one I can see is left of the point where the top most "dark spider" cuts the top of the image ('bout a quarter of the way across). running about 45 degrees top right to bottom left, bright against the dark background. There are others too

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  • wassock by wassock moderator

    Oh yes Kith there's loads and much more visible in APF0001epp

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  • Kitharode by Kitharode moderator

    If these hair lines are the same as those in the images shown in 'Yardangs - More Interesting...' then they are not permanant features. We've been told that the hair lines in the other images disappear in summer. Maybe this is a thin transluscent layer of ice displaying some polygon fracturing .. ?

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  • angi60 by angi60

    Hi. So are the 'hairlines' that you can see on ice-free images of yardangs a different feature? (Just curious!)

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  • Kitharode by Kitharode moderator in response to angi60's comment.

    The difficulty I think, in certain images, is recognising when it is ice-free and when it is covered in thin transparent ice. I've a feeling that some images look ice-free but may in fact be 'coated' with clear ice. If that were true, then the ice-coat could fracture with hairlines that will disappear with the ice. All guesswork at the moment.

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  • wassock by wassock moderator

    The "typical" yardangs with fine lines look like this. APF00009du

    I think that the. Images above are late season ones (just a hunch) without the ice thinning but the look of the fine lines is very similar to the typical model

    In APF0001epp there are several dark lines with a bright halo, mostly on the left. Any ideas on these?
    Also When you try and zoom the image appears grainy/unfocussed more so than. Normal?

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  • wassock by wassock moderator

    Kith I see the polygonal fracturing involving mostly straight lines or a constant curve between two points or corners of a plate. The fine lines are not like that, more like hairs on the lens.

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  • angi60 by angi60 in response to Kitharode's comment.

    Ah I see - I didn't think of transparent ice. I'd always wondered about the hairlines, hence the question! Thanks.

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  • wassock by wassock moderator

    Curiouser. If you open the image above in a new tab you see it as a JPEG with associated URL and image number. Looking at the image refs above and below this one you get images like this. http://planetfour.org/subjects/standard/5143480dea305267e900590b.jpg which looks to me like early season in the same area. These images also seem to be low resolution

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  • Kitharode by Kitharode moderator in response to wassock's comment.

    Wassock. Your 'hairs on the lens' analogy is perfect. Thin hairlines that meanderer 'over' the general terrain. Sometimes long and lonely, but often giving the impression of a 'net' cast over the background terrain. An organised collection of the same areas at different times might help. Have to hand that job over to the wizard department - way beyond me. 😉

    No ideas at all on the white halo's.

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