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Tubes on Mars
Glass, Lava, Worm? Or. . .?
Tubes of Light and Shadow
What are these strange and wonderful shapes? They seem to be showing up
everywhere on Mars, particularly in the polygonal terrain of Acidalia Planitia.
Are they glass tubes as some Mars watchers are speculating? Are they giant
fossil tracks or trails of some giant extinct creature? Worm tubes? Or is
there a geological explanation?
Since we have no samples and no one has been to Mars, nothing is certain.
We only have long traveled and sometimes deceptive images to use when doing planetary
geology, and little on Earth to compare. Vegetation and water cover
our home planet. A dynamic geology is constantly changing Earth's appearance.
What happens here does not necessarily happen on another planet.
The emergence of living organisms and their extinction, though recognizable,
most likely will be different on another planet. We can, however, use what
we do know about our own rocky, watery world to decipher the mysteries of a
similar planet's geology.
Tubes and Tunnels?
Here is the image that is causing so much controversy.
It can be found at Malin Space Science Systems
MOC narrow-angle image M04-00291. It certainly looks
like there could be some kind of tubular structure there. Various people have
played around with it and attempted to explain what these structure are - most
notably Richard C. Hoagland and his team at
Enterprise Mission. Some say
they are tunnels. But are they? We need to compare
these "tubes" with others in the area. We must make an effort to see deep
within the shadows of this tortured polygonal landscape.
It would be incredible if these were tubes.
However, every geological process that could produce this landscape,
including the "tubes" must be
considered. The basic attributes of this area - how and why it looks the way
it does - must be considered. Optical effects and tricks of light and shadow must be
considered. Then we can look at the prospect of intelligent
construction. Fossils fall into a geo/biological category. But the landscape must
be considered first, as fossilization usually happens in some kind of depositional
environment. In the case of worms, and other burrowing animals, the original environment
would most likely have to be some kind of soft sediment, sand or soil, or
water.
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A Closer Look
Click the image on the left to see a larger view.
resize and scroll if needed
This image is from the
MOC Image m0400291 - Browse Page at the Planetary Image Atlas PDS website. The
orientation here is true, and it has not been enhanced by anyone - except perhaps
by NASA or the USGS. Any changes or enhancements I make will be my own.
Yes, it looks like tubes. Or intersecting worms. Worms will group together.
I see them tangle together in my
can-o-worms composting unit and in the compost bin out back. And they
can stick to just about anything. But tubes or tunnels hanging over what looks like
shear drops into dark chasms or fissures? How can that be?
Both Malin Space Science and the Planetary Images sites call this
sample of fine channels. The work of streams is involved in many geological
situations. Stream erosion manifests itself in many different ways according to how the stream
forms, what it transports and deposits, and the environment in which it exists.
There are plenty of depositional and erosional features in these images. I will
examine some ways that channeling could have happened here.
This image (39.12 ° Latitude, 27.08 ° Longitude) is near to another
"tube" image, m0201270 (38.98 ° Latitude, 28.35 ° Longitude) which is described as
Giant polygons in Acidalia Planitia. If you search through the images at these
websites you see that Acidalia Planitia appears to have
quite a large population of 'worm/tubes" (for lack of a better discription, under these
circumstances). This suggests that the structures
were probably all formed by a similar process and at about the same time. I will explore a few of those
processes using these images, as well as other wormy places in Acidalia Planitia.
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More Light
Click to see larger image
resize and scroll if needed
First we have to get some light into those dreary crevasses. Following along the dark
edges with the dodge tool I was able to bring out some of the rocks that are in deep
shadows. It is not a very neat job, but it serves the purpose.
One can see in the deepest places there
just was not enough light for any kind of image to come through.
Any more dodging would only wash out the image. This image does not add
much new information. But one can predict what is down there - more rock, rubble and debris.
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Mars Global Surveyor MOC Image m0400291
| This is the m0400291 image from the
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I put the three sections of the image
together. Click on it for a large image.
(opens in new window)
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We need to determine what this topography is.
Correlation
Identifying other examples of a geologic phenomena
in this case geologic images
Another Wormy Image
Click the image on the left to see a larger view.
resize and scroll if needed
This MOC image, m0201270, is titled Giant Polygons in Acidalia Planita. It is
38.98 ° latitude and 28.35 ° longitude - right next door to the m0400291
image. It comes from its
Panetary Image browse page and the orientation is true.
The structure in question may still have a worm or tube-like quality to it. However,
if you look carefully you can see that that material seems to be pulling away (slumping)
en masse from the rest of the land. The same thing seems to be happening in image, m0400291.
The same type of polygonal fracturing and fissuring is happening in both images.
However, the pulling away and sliding might be an optical illusion - a trick of light and
shadow like worms or tube shapes. Maybe. In a different light what appears to be arched
and rounded could be just the opposite. Maybe not. Some "tubes" or "worms" I have found in
other images defy explanation - at this time.
You can see deeper into the crevasse here. Obviously these are very deep and dark
places.
- three cropped images -
- lightened -
- Click a larger window -
They may make it easier to see in the shadows.
Very Large m0201270 Image
In the first and third cropped images the "tube" does not look much like a cylindrical object. It appears
to be coming down from the adjoining fissure or canyon wall. Possibly this is a stream
terrace, formed when a wider stream flowed through here and helped to form the polygon.
It is also possible that it slumped down to this position. Many Earth images taken from
high altitudes in greyscale show water in channels and lakes as being very dark - black.
It is possible that a younger, deeper stream is at the bottom of these canyons or
crevasses. The third image shows the polygons intersecting. It looks like mud or debris flows at the bottom.
In the second cropped image the "tube" seems to rise up and tapper into almost nothing.
But you can see the faint relief of where it trends and where it stopped falling away from
its parent body. A stream may have slowed down or stopped altogether. Or something happened - a
tectonic force perhaps - to disturb the scene.
This image shows the area directly above the second one. The lower part of the polygon has
broken away from the upper part or the land has shifted. This suggests that there may have
been more than one period of polygon formation. Or this could indicate faulting - horst and
graben processes. The thick arrow shows the direction of movement.
Processes such as these might create the odd looking worm-like structures seen in many of
the images from this area.
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So what is all this stuff?
There are several interesting images from Acidalia Planitia.
MOC image, m0001504, on the
Planetary Image Browse Page, latitude 36.13 °, longitude 28.57 °, and
true orientation - contains another intriguing worm like structure.
At first glance it looks cylindrical. It looks like the earthworms
in my garden. But on closer examination it appears to be part of a forming polygon - just
before the really deep fissure appear. Or maybe the fissures are deeper than I can see. Maybe this is
down drop graben faulting, or slumping. Maybe a giant worm has been caught in a landslide.
Whatever - a pattern begins to emerge here. It could be an illusion, but these structures
are seen fairly close to the top of the polygons. And,
interestingly they are usually on one side only. Some appear to be coming away from the land (or maybe ice) and some
look like giant worms moving through the soil. The interesting thing here (at least in
this section of Mars) is that they all are found at the margins of the polygon.
If they are not at the margins, then they are located
where a polygon fissure is taking shape or where some other deformation or movement occurred.
(or is orccurring)
Third segment of MOC image m0001504
Click for larger window
larger image
(opens in new window)
There are many things here, and in the rest of image m0001540, that suggest the workings
of frost and ice, and possibly thermalkarst activity. These polygons could be ice-wedge
polygons. Or a combination of ice and something else - something unique to Mars. One theory
about Martian polygonal ground is that it is volcanic. Lava could have made lava tubes. And volcanic forces produce grabens.
Mudcracks are polygonal as well. I suppose it is possible to have giant mudcracks on Mars,
but polygonal ground is most often associated with freezing and thawing.
A polygon is a figure or plane having many sides and/or angles, usually more than
four. In geology polygon describes many things. Polygonal ground is defined as
level or gently sloping ground marked by polygonal arrangements of rock, soil and
vegetation. Freeze-thaw action produces polygonal ground. The surface often has
a network of large-scale ice-wedge polygons.
Ice-wedge polygons are formed by contraction of frozen ground and permafrost.
Intersecting and fissured margins of ice or icy materials make up the polygonal surface. Frost-crack polygons result from intersecting frost cracks. Frost cracks are
vertical or nearly vertical fractures caused by thermal contraction of rock or frozen
ground. Fissure polygons are made up of intersecting grooves or fissures.
All three polygons - Ice-wedge, frost-crack, and fissure - could be acting upon
the landscape of Acidalia Planitia. And maybe more. It is pretty safe to say that
freeze-thaw conditions exist on Mars. There probably is a lot of unsorted
material, moving around and breaking up as ground ice and frost melt and refreeze.
As we receive more images we will see come to realize Mars has a active geology after all.
Constant alternation between freeze and thaw will eventually break down rock and soil.
Soft, wet, churned up material will wash away if there is enough flowing water during
periods of thaw. Flowing water later refreezes somewhere else, along with the materials
it transports. Under these conditions the landscape is always changing. Land sinks as
permafrost thaws and/or water leaves the area. Land rises (albeit slowly) as glacial or
stagnant ice retreats. Surface breakup, if there is sufficient water in the rock and soil,
can cause all kinds of interesting patterns and effects.
Anyone who has lived in cold climate knows lots of things (good and bad) happen to a frosty icy
ground. Potholes form when ice lenses below the surface melt.
Rocks and roots push up from below the soil. As soil swells upward during freeze it brings new
material to the surface. Hard ripple-like wavy patterns, as well as polygonal shapes,
appear on the deformed surface, only to fall away when they thaw. Large quantities of
melting ice produce temporary streams. And streams of all kinds cut into the
landscape and transport materials to other locations.
Large-scale spring break-up might have regularly occurred in Acidalia Planitia, if it
were warm enough and it had enough liquid water moving through the area.
Mars may have experienced a major
catastrophe such as a massive volcanic or impact event which might have resulted in the melting of permafrost and
glaciers, followed by the loss of most of the planet's water. Or such an event could have
resulted in the loss of surface water and ice followed by freezing of ground water.
Either way, the
result could have been a lot of cracking, fissuring, subsidence, uplifting, down
dropping, churning, crunching, transporting, depositing - an all around, general
'smash-em-up' event - a hummocky and polygonal terrain.
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-- Credits --
NASA - JPL and NASA Image Use
- three cropped images -
- lightened -
- Click a larger window -
