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Nirgal
2004-Apr-24, 12:32 AM
motivated by the recent discussion about the possible "crater lake"
(although dark sand/dune feature is more probable IMHO)
I would like to hear your opinion about a even more stunning image
of what really looks like a frozen lake:

http://mitglied.lycos.de/user73289/misc/E1002102_crop2.jpg
[/img]

The location is in the southern polar area where temperatures never
rise above freezing, so couldn't it be a (thin) layer of preserved ancient frozen water ?

any other explanations ?

original source image at:
http://www.msss.com/moc_gallery/e07_e12/images/E10/E1002102.html

JustAGuy
2004-Apr-24, 06:10 AM
Wouldn't water ice have to be constantly replentished, otherwise it'd sublime away in a (relatively) short period of time?

Sure, it looks like an iced-over lake on earth would, but we have to keep in mind that the picture isn't of earth.

But still, that's one interesting picture, even if it isn't water (or is, I don't know enough to say with authority). I'd love to hear analysis from people smarter that I ;)

eburacum45
2004-Apr-24, 07:26 AM
Perhaps it is evaporite;

a salt lake deposit, probably a sulphate salt of some kind...

JonClarke
2004-Apr-24, 09:15 AM
Very interesting image, especially the smoothness of the dark material. Ice at that latitude would not sublime, it is too cold, which is why the polar caps survive. the problem I have with a frozen lake is that lake and sea ice on earth is normally white, not dark.

Jon

johnwitts
2004-Apr-24, 11:34 AM
Very interesting image, especially the smoothness of the dark material. Ice at that latitude would not sublime, it is too cold, which is why the polar caps survive. the problem I have with a frozen lake is that lake and sea ice on earth is normally white, not dark.

Jon

Could be an IR image. That way, cold = dark. Maybe.

Nirgal
2004-Apr-24, 05:00 PM
and yet another one :)

http://mitglied.lycos.de/user73289/misc/R0502361.jpg

JonClarke
2004-Apr-25, 03:39 AM
Very odd. Is this one of the areas where CO2 snow has submined exposing water ice?

Jon

ChaosInc
2004-Apr-25, 02:18 PM
It does have an appearance, at least superficially, similar to the hot springs pools at Yellowstone. I suppose the striations in the second picture are photographic artifacts? The second photo also has places that could be the site of upwelling, but I tend to see what I want to see.

PeteB
2004-Apr-25, 02:38 PM
Nirgal -

Is this a MOC image? Do you have a link to it at MSSS?

It is sometimes difficult to tell if an isolated feature is positive or negative relief. As this image is posted I see it as a depression, but flipping it around 180 deg. turns it into a mound. Having the ancillary image data so that the sun direction can be determined is frequently necessary. There have been MOC images near the South Pole touted as "lakes", that, instead of being depressions, I think are actually remnant patches of CO2 ice that have positive relief. The orientation of the image and the inferred direction that the light is coming from is being misinterpreted.

Nirgal
2004-Apr-26, 06:55 PM
Pete,

I am aware of the positive/negative relief problem. just think about the (in)famous "golf-ball" in a crater-image (not to mention the "worms" ;)

... but pareidolia is not what i'm into ;) ;)

here is the link to the original image

http://www.msss.com/moc_gallery/r03_r09/images/R05/R0502361.html


sunlight does seem to come from the upper left

Nirgal
2004-Apr-26, 09:55 PM
and here comes the next one:
http://mitglied.lycos.de/user73289/misc/R0702302.jpg

from the crater to the right it is obvuious that the sun illuminates the scene from the upper left, so it's actually an depression/basin,
not a plateau ...

could this be be an (ancient ?) lake bed ??