may have the characteristics necessary for karst geology to occur. Karst topography typically exists over carbonate rock such as limestone, dolomite and marble. Karst also forms where there are evaporites such as gypsum, rock salt and anhydrite. Basically, these are rocks that dissolve in water and precipitate out of water to form rock again. Carbon dioxide in groundwater dissolves carbonate minerals as it moves through the spaces and cracks in the rock. Over time, this process enlarges the spaces. The water often leads to an opening at the surface, creating springs or entering streams. As streams cut into the landscape, the water table is lowered. When the water level drops sufficiently, these spaces become empty. Thus, a cave is created. Most karst activity is carbonate in nature, and is replenished by the carbon dioxide in rainwater. Like volcanism, it is part of the carbon cycle. Cave formation can also happen as hydrogen sulfide, rising from great depths, goes into solution and produces sulfuric acid.
Could there be caves on Mars? There are several types of caves on Earth, and distinct karst regions. They vary, according to the rocks, the climate and geological processes at work there. For example, in humid-temperate zones of the US and Europe sinkhole karst is common. Tower and cockpit karst are found in humid-tropical zones such as Puerto Rico and southeast Asia.
Steep-walled hills, rising from flat valleys or plains are characteristic of
tower karst.
These are the strangely shaped towering hills, depicted in classical
Chinese art.
Could they also be the strange pyramidal structures found in Cydonia?
Cockpit karst consists of conical hills and polygonal sinkhole depressions.
The
Arecibo Radio Telescope Observatory in Puerto Rico is built into a sinkhole in
tower and cockpit karst terrain.
Interior valleys are closed depressions with steep walls and flat floors.
During the rainy season, the water drains into caves. When the caves are not be able to handle especially heavy rain the interior valley often becomes a temporary lake. During heavy rains many
sinkholes also become temporary lakes as well. Deep sinkholes often retain their water, making excellent, but often dangerous,
swimming holes.
Sea caves are formed along the shoreline. Waves attack the base of sea cliffs and wear away the rock along faults and weaker beds. The harder rock above becomes the roof of the cave as the softer materials are washed away.
Lava tubes form when the outer surface of a moving tongue of lava solidifies. The molten interior continues to drain downslope. Tubes usually form in basaltic lava, which sometimes tends to flow and branch out, rather like a stream. When flow stops a tubular cavity remains. My guess is that there are many lava tubes on Mars.
Sandstone caves were more commonly used for shelter than limestone caves. They are shallow, easily accessible, warm and dry. Limestone caves are typically damp, cold and dark. Sandstone caves form at the base of cliffs where the materials in the lower parts of the rock are less cemented than above. Surface water moving down the cliff dissolves the cement. Sandstone such as this is easily carved. The cliff dwellings at
Mesa Verde are an example of sandstone shelter caves.
Sometimes caves or domepits are formed as water sinks through surface soil, and overlying rock. This process is a little different than cavity formation at water table levels.
Domepits and vertical
shafts continualy enlarge as acidic water moving down from the surface dissolves the
soluble minerals.
Another form of karst, thermokarst, occurs in the Alaskan Arctic and other
permafrost regions. The
Arctic Coastal Plain in Alaska has such topography. When the thin upper layers of soil
and rock thaw, the water is not able to percolate through the thick permafrost below.
Sink lakes, depressions, cave-ins, and bogs form.
These same processes could have happened on Mars. In all likelihood, they did happen on Mars. Time to take another look at some of those indecipherable Martian craters.
Another Enhancement
A photo filter was used to color this enhancement. It seems to bring up some of the features, particularly the lighter materials. The symmetry of the entire structure is very obvious. The depth of the depression is clearer.
There is much debris at the bottom of this hole. And there doesn't seem to be any drainage outlets. There might be adequate drainage on the sides of The Face structure but not in this basin. This depression is enclosed and lacking evidence of surface stream drainage. Under these conditions, assuming that water existed here, drainage could only be subsurface. Sinking streams and losing streams - streams that carry water directly underground - are characteristic of Karst systems. This basin looks like it might be a sinkhole, or several connecting sinkholes. Or it might be a large cavern with a collapsed roof.
I would like to note, there are a lot of enhanced images of The Face on the Internet that show a rather wide opening at the northwestern portion of this depression and/or sinkhole. It becomes increasingly difficult to distinguish which image shows the true features and which does not. I have already talked about the deceptiveness of enhanced images. I am using this enhancement, originally from Steve Wingate's MaxEnt enhancement, while constantly comparing and contrasting it to the work of NASA and others. Looking at the deposition and erosion - sliding and slumping - it seems to me that the widening and opening of any entrances to this basin may have occurred (if it is there at all) after its formation.
Rotated 180 °
The top portion of The face is rotated 180 degrees, which reverses everything, and shows the erosional features of the basin's southern wall. Notice at the top the slab-like overhanging rocks, and the bare areas beneath them where the land has slid away. Other debris piles, talus and rubble are clearly visible in this image. But notice also, how rotating the image changes the perception of some of
the features seen in the upright position.
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Sliding and Deposition
on the north and south walls
Click on them to view
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This does not look like an inactive terrain. It looks as if the slumping and sliding in this basin, as well as on the outer boundaries of the structure have been going on continuously for quite some time. And it looks like several processes have been, and are, involved in the shaping of The Face.
Water and ice on and below the surface determine the shape and hydraulics of the land. So do earthquakes (marsquakes) and volcanism. Drying and shrinking occur with the removal of liquid. Withdrawal of fluid is another way subsidence and shrinking happen. Decay and chemical weathering always happen. The Martian atmosphere itself probably plays a major role in the chemical breakdown of surface materials. And then there is the Martian wind - with its heavy particle load. It would seem The Face is collapsing in on itself.
SINKHOLES
This Earth sinkhole has slumping features that look almost identical to those seen in the images above.
Sinkholes can be very large and treacherous. They often form quickly and
without warning, when something has greatly disturbed the subsurface environment.
A sinkhole (also called sink or doline) is a collapsed portion of soil and/or bedrock. It is often over a subsurface void, but collapse can happen as water and other materials such as lava, gas and hydrothermal fluids, are drained away.
A sinkhole may be just a shallow depression in the landscape, or a deep vertical shaft or dome. Collapse can happen when the supporting dome rock weakens.
Some caves and sinkholes have water all year long. Some flow with the seasons. In time, the
water will move downward, sometimes into other open cavities, sometimes creating new
ones. Caves are often multi-layered, with several "floors", shafts and passageways to a
system.
Some sinks and caves have small openings an are treacherously hidden from view.
This hole has a limestone roof and the water is 4 feet below. The owner of this image describes the water as "tannic". With all this foliage about, the water most likely carries a lot of organic debris. Organic matter is a source of carbon. Carbon from decaying organic matter contributes to the acidity of the water.
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Massive sinkholes are continuously forming in the Dead Sea region where mineral rich water is being diverted to evaporation ponds. In addition, earthquakes and faults displace drainage channels.
Absence of fluid or other substances is a key factor here. Think about a region, such as the Dead Sea where minerals are constantly harvested, or a planet, that is rapidly loosing fluids and other materials - through natural, catastrophic, or intelligent design. It is not difficult to picture karst geology, in all its many forms, on Mars.
Mike Emanuel's Cave Diving Page
A great sinkhole and cave diving site
The Top in 3D
The top portion of The face in 3D analglyph. The depth of this depression appears more evident. Other circular depressions above the basin (bottom portion of image) are also more pronounced. These could be sinkholes as well.
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TheTop in 3D - - Rotated 180 °
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Both Images Together
The two images, one rotated and one upright, seen together in order to compare the features of the northern and southern walls.
Again, the viewer must realize that rotating or flipping an image of this nature tends to distort the features. I think that this can be one of the ways Face
watchers, myself included, get confused. And it makes me wonder - it makes me suspicious of all the NASA Face images. Because they have created their own enhancements. So, who knows anymore which image is true to the actual structure and which is not? Thus, all enhancements become
suspect.
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Right side top, Rotated
This image and the one that follows are really not very clear. I added them to be thorough.
The right side of the top turned counterclockwise to see this end of what I think may be a collapsed cave or sinkhole. This side is narrower than the left, and is completely closed in.
The trenches or terraces (or both) along the outer portions of " The Face are easily seen here.
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Left side top, Rotated
The left side of the top turned clockwise to see that wall and the deposition there. On the lower left side of this image you can clearly see the small depression in what might be the eye area of The Face. It appears to extend narrowly across the structure, as if its contents broke loose and cut its way to the other side. What might that contents be? Water - ice perhaps? A drainage outlet for a cave?
The left side of this basin seems more gently sloping and wider than the right side. Perhaps it is made of softer, more easily eroded material. The large pile of debris at the bottom is the same as in the first image. Again, image distortion is at work here.
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NASA'S Image - - My Enhancement
Just to be silly, I made my own, rather simple, enhancement.
We really need a better picture than this.
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Page Three
In Search of the Cydonia Face
