Planet Four Talk

Boulders on 'tors'

  • p.titchin by p.titchin

    This is a fascinating image, as is the bigger area on the HiRise picture.Anyone any comments? The density of small blotches is unusual, these become so dense in the area above on the HiRise strip, the image is almost black. The high spot and boulder clumps are also odd, given the flat surrounding terraine.

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  • Kitharode by Kitharode moderator

    The HiRise image is centred on 69 deg S and 355 deg E, which puts it outside the area of the polar layered deposits and into the more 'general' martian landscape.

    The area is littered with the remnants of ancient craters. Over time these 'ghost craters' become washed-out as they fill up with material, creating a somewhat smooth landscape littered with the protruding remains of the crater walls.

    The surface material of the area is darker than the 'usual' martian dust because it lies between the dark dusty Mare Australe and Mare Amphitrites.

    The image was captured a little before the southern spring equinox (Ls = 173.2 deg) so the area should still be covered by the seasonal icelayer, but we should not expect sublimation and venting at this time.

    Boulders: A complete mystery to me. Sorry. ** 😛 **

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  • p.titchin by p.titchin in response to Kitharode's comment.

    Thanks, Ive only been seeing the polar images, so this made no sense to me. Much appreciated explanation.-- Boulders!!!! they seem to make no sense, I have come to the conclusion that we are probably looking at very different features with different aetiology. It would be great to know their make up. I would be surprised if they all had the same composition.

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  • Kitharode by Kitharode moderator

    I'm sure you're right in thinking that the make up of boulders will vary. We know there are boulders 'made of rock' on Mars which probably vary amongst themselves and (somewhere buried in the discussions) I'm sure Meg suggested that many polar 'boulders' are, at least in part, made of ice. Perhaps Meg will spot this and make comment.

    Even more interesting, for myself at least, is the location and distribution of boulders. They can be found isolated, in small groups, formed into boulder fields, shaped into concentric rows, and sometimes surrounding spider formations. As to the how and why of all this, I'm afraid I've got no ideas at all.

    It's perhaps worth noting that there doesn't seem to be much written (known?) about southern polar boulders which, if true, makes this a genuine target for citizen scientists. Over to you then... 😉

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  • wassock by wassock moderator

    Anyone bin and looked at the hirise pics? TheRGB JPEG has what looks like a big blob of solderon it. Closer inspection makes this a likely location for the original pic, which the grey scale image reveals to be the bottom of a girt big hole.

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  • Kitharode by Kitharode moderator

    I looked at the 'RGB non map projected' image. It's got the big solder blob on it. Haven't seen the girt big hole yet - can't wait.

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  • angi60 by angi60

    I've also noticed that on similar images to this, the 'blotched' effect is often an unusual greeny shade, a bit like the colour you can get with copper. Anyone know why?

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

    I'm pretty sure I know which images you mean. Some of them are a bit like 'unfocussed' 3D images, yes? These images seem to me to have appeared quite recently on site, perhaps coinciding with the recent release of the 'season one' image collection. If I remember correctly, there was a dust storm in the first season of images (needs confirming) which could well affect the images.

    Or perhaps it's Mars, not the Moon, that is made of green cheese ... ** 😛 **

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  • angi60 by angi60

    Yes that's it, though I'm sure I've seen some of the images some time ago. Then again my memory is not always...... What WAS I saying?

    Haha - must be very mouldy cheese! 😮 Seriously though they're very interesting images - very distinctive. They have 'track-like' patterns on them too (polygonal cracks?). Remind me of an awful 1970's carpet design!

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  • p.titchin by p.titchin in response to wassock's comment.

    I looked at the 'solder blob' when I located the original image on the RGB,as it is almost on the edge of it., but I was already too bemused to mention it. Sure is a gurt big hole!! I will await further discussion of it with interest.

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

    Angi, my feeling is that colour is more to do with the camera than any sort of mineral deposits most of the time. Have a look at the images here http://talk.planetfour.org/#/boards/BPF0000008/discussions/DPF0000cbw

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

    Thanks Wassock. That's very useful 😃 I did wonder if it was the camera. Even ignoring the colour it's still very distinctive terrain!

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  • wassock by wassock moderator

    Anyone else see a channel leading away from the hole? Bout half way up on the greyscale JPEG going off to the left.

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