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Tubes on Mars

All
the segments of image m0001504, titled Lobate bright/dark contacts on Acidalia Planitia have features that strongly suggest glacial activity. For instance, many small depressions look as if they contain ice. I, for one, do not believe an impact crater created every hole on Mars. Many processes leave holes behind, like dolines, karst lakes and kettles to name a few.
Kettles
are depressions in glacial deposits (drift). A depression forms when a mass or large block of buried ice melts. Kettles can be large and often contain lakes. Presently on Mars kettles would contain ice. It is possible that, along with sinkhole plains, caves, thermal karst, etc., Mars had kettle lakes and landscapes resembling the region around the Great Lakes of the US and Canada. Kettles are commonly associated with Kames.
Kames
are mounds, knobs or ridges of stratified glacial drift. There are several ways to make a kame: Stream deposits of subglacial channels - in much the same way as normal surface streams. Fans and deltas are common subglacial stream deposits. Deposits from streams on top the glacier that empty into holes or crevasses. And from sediment and materials that come to rest on top of stagnant ice or in superglacial ponds, ditches, crevasses, etc. These deposits are left behind when the glacier retreats.
Kame
terraces are stream deposits between valley walls or lateral moraines and masses of retreating ice, such as melting glaciers, glacial tongues or a body of slow moving 'stagnant' ice. A stream tends to sort and deposit materials according to grain size and its ability to transport its load. This is how stratified layers develop. After the glacier is gone, stratified deposits of sand and gravel remain in terrace like ridges.
Similar
to kames, eskers are long narrow sinuous ridges. They form under stagnant or retreating glaciers which have very active subglacial streams. Their sinuous pattern reflects the meandering channels that made them. Eskers often come in pairs, as there are two sides of the stream. After the glacier is gone a lake is often left between a pair of eskers.
These
structures are commonly found together, in hilly hummocky glacial topography - vast areas (fields and valleys) of kames, kettles, lakes, streams, ponds, eskers, terraces, ridges, flutes, polygonal ground, and various types of moraines.
Acidalia
Planitia seems to exhibit this topography. Perhaps it was glaciated. If it were, then after the ice retreated, or melted because of some catastrophic event, the land would lose the support it had for so long. Deformation, isostatic rebound, slumping and collapse are sure to follow after all that pressure is gone. You can think of a kettle in this way. The ice leaves and the land collapses. Or the ice melts and remains in the collapsed space as a lake. A Kame terrace, or part of it, will slump or collapse when the retaining ice walls are no longer supporting it.
Is
it possible that the worm/tube shapes formed in such a glacial, or semi-glacial, enviornment?


A section of Acidalia Planitia.
possible glacial features

Reference Image PopUp Window - medium size

Click thumbnails for larger image pop-up

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In
the first image above there are what I think could be kettles, maybe old kettle lakes and ponds. I wonder if the light material in them is ice rather than newly deposited sediment. There could be a combination of both in them. Some of the lighter surface material may be waterlogged or slushy soil containing ice. What happened on the lower left side? Did a worm/tube slide sideways? Did something push it? Is this a Martian kame? A block of ice? Or just a rock?
The
second image above has a couple of interesting "anomalies" in it. One "tube" looks quite cylindrical. The other is not so clearly defined. Have they moved, or been moved, like the one in the other image? Is something coming over them from behind? The rather fluted looking surface in front looks like it was there first. I can't say for sure if that is glacial fluting. But it looks like it could be. Then again it could be a lava flow. Something certainly came over the land and made that pattern. It could be part of the polygon formation process. Maybe it is all this. These labels are really only guesses at this point. It is hard to tell if that is crater, a mound, or knob sitting next to the worm/tube. Is it an optical illusion? If so, that would probably make it a crater. If it is a crater, did it come before or after the appearance of the tube? It is covered, or filled, with lighter material. The general opinion is that this lighter stuff is the most recent sediment. That could be so. It could be seasonal ice.
The
strange thing about this image is that cylindrical looking thing on the upper right side. I just don't know what that is. I don't know what in nature makes a shape like that. If I invert the image it looks like a depression. But is that right? What about the rest of the image? Inversion reverses all the darks and lights. Is that really how this image is supposed to look? The end of the cylinder is totally black, but totally white in the invert. That's the trouble with images that have such black shadows. If there is no light, there is no information. Inverting them only gives you white - still no new information. You can't possible see what is there.
Tricks
of light and shadow: If I forget the notion of an intelligently designed structure and go with the idea of a glacial topography, the only thing that comes to mind is some form of kame or ridge. Or possibly an eratic boulder. Whatever it is, it could have ended up in this situation after something disturbed the landscape.

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The
first image above shows either a slump, a debris flow, a graben down drop, or part of a polygon. Everything, except the slump has the markings of trending diagonally down the image, from top right to bottom left. The land above the slump looks furrowed. The slump has a more disorderly look to it. Although the slump is heading the same way, a ruffling and buckling of the material - like furrows and ridges - caused by the motion of the slide is running in the opposite direction.
The
arrow in the second image shows the general direction things seem to be traveling. The upper part of the image looks like furrows or trenches of some sort - small grooves and ridges, possibly glacial fluting. I am not sure. Glacial fluting in this instance is a series of grooves and ridges in glacial till. It runs in the same direction as the ice flow. But it could be furrowing produced by other mechanisms. It could be a field of kettles and kames. Till could be made up of anything carried and deposited by the glacier - silt, sand, clay, gravel, or boulders. If the other things in this landscape are indeed glacial features, then till could be here as well.

Other scenes from
m0001504 Browse Page
"Lobate bright/dark contacts on Acidalia Planitia"
(And Worms)

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NOTE: Links in text below for segments of m0001504 are for large images and open in another browser window.
Segment
A
from m0001504 is a messy image, but it has some neat "worms" in it. The worm shape in the first image above looks like it could be a drumlin. It even appears to have a shadow. However it is not orientated the way drumlins are on Earth. A drumlin is a streamline asymmetrical hill, shaped rather like a whale. Its steep side faces the glacier. Its tapering gently sloping side points in the direction of the glacier's advance. But this "worm" is not running parallel with the trend of the terrain. Drumlins usually come in clusters, sometimes called drumlin fields or swarms. This does not seem to be the case here - unless I am seeing this all wrong, and the fluting is the drumlin field.
Drumlins
are depositional features, formed within the glacier and composed of till. No one knows exactly how they form. One good idea says they were made when a glacier advances and reshapes an old end moraine, then retreats again. But this is probably not what is going on here. A polygon fissure is probably opening up. If you look closely you can see a depression running up from the worm to the top left - the markings of a polygon perhaps. The "worm" in the second image above has the same shape, but it is facing in a different direction.
The
third image is from segment B. It is the strangest looking one of all - totally perpendicular to the straight diagonal trend of the rest of the terrain. Is this just a fabulous example of light and shadow illusion? In another image (small window) I drew lines indicating the path of the fissure - another possible polygon, either failed or in the process of forming. Arrows indicate two possible paths the fissure could have taken. It looks like some sliding has taken place during formation or after the fissure began to open


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The
first image above, also from segment B, shows the lobate bright and dark contacts. I am not sure is meant by this. It probably means any lobe-like feature - some globular mass. Lobes usually are an extension of something else. A glacial lobe, for instance, protrudes from the margin of the glacier or ice sheet. There are no active glaciers here. But there probably is permafrost. It definitely is a different substance than the rest of the land. Maybe it is ice, or ice covered with dust. Maybe there is a low fog or mist covering it. It could seasonally freeze and thaw. Perhaps some sort of frosty substance is sublimating. Whatever it is, it is very interesting. It is going to take several seasons of Mars watching and imaging to really know what is going on here.
The
last image is from segment D. It looks like a couple of polygons are forming - and another worm too! Arrows indicate direction and where the worm has split apart. There could be some faulting happening here too. Clearly these worm/tube structures are part of the caverns, crevasses and fissures that make up the margins of the polygons. Over time, and with all these powerful forces at work - freeze-thaw, tectonic downdrop and uplift, possible down cutting seasonal streams, glaciers, volcanic activity, impacts, etc. - many amazing structures are sure to manifest themselves.



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-- Credits --

NASA - JPL and NASA Image Use