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cuboctahedron
2004-Apr-23, 01:31 PM
An interesting image at:

http://www.geocities.com/cuboctahedron2004/lake.jpg
http://themis.asu.edu/zoom-20040422a.html



We chose this area because of the presence of craters in the vicinity, which we hope will help with our thesis about the presence of craters that contain lobates as use for evidence that there might once have been water in this area.

This image is causing us considerable difficulty due to the presence of a structure that resembles a lake located in the center of the crater.



Could this indeed be a lake?

Patrick

ToSeek
2004-Apr-23, 02:30 PM
That's a very interesting image. Not only does it look like a lake, but it looks as if there's a stream feeding into it. Do any of the Mars orbiters have the equipment to determine if that really is water?

Vernors
2004-Apr-23, 03:33 PM
Isn't the atmospheric pressure on Mars too low to allow liquid water on the surface? It was always my understanding that it would boil away almost instantly at that pressure.

cuboctahedron
2004-Apr-23, 03:38 PM
Perhaps if there is a continious stream of water, it might hold enough to form a lake. (also, perhaps there could be a thin layer of ice on top)

Vernors
2004-Apr-23, 03:53 PM
Perhaps if there is a continious stream of water, it might hold enough to form a lake.That's possible, I guess, but it would have to be replenishing the water in the basin at the same rate that it was boiling away from the surface. Given the amount of surface area shown in the image that I would think you'd need a lot of water flowing in.

Wingnut Ninja
2004-Apr-23, 04:03 PM
Well, it looks like it could be some sort of dark sedimentary deposit instead of liquid water, but either way, it's pretty cool. It definitely doesn't look like it was just shaped by wind.

cuboctahedron
2004-Apr-23, 04:28 PM
A brighter closeup of something that appears to be a sort of a spring, creating a stream.

http://www.geocities.com/cuboctahedron2004/lake2.jpg

Nirgal
2004-Apr-23, 04:59 PM
definitely worth a shot with the high resolution MOC camera
(about 2 to 4 times better resolution than the THEMIS image)
maybe we could suggest this area for the MOC "public target"
program at

http://www.msss.com/mars_images/moc/publicresults/

however, I'm afraid it's not a lake but some dark sand/deposit stuff
forming yet another "dark single dune"
like there are so many inside the craters ...
Also, for a lake, the "shoreline" does not look "rugged" enough ... it rather looks "smooth" like the shilouette of a large dune ...

cuboctahedron
2004-Apr-23, 05:11 PM
I am inclined to say it's a pool/little lake.

IF it was a hill or sand pit, it would have had at least some faint surface features.
About water in general: streaks have been detected on Mars elsewhere, that had been formed by recent water flows.(it has been discussed many times already, I believe)



Also, for a lake, the "shoreline" does not look "rugged" enough ... it rather looks "smooth" like the shilouette of a large dune ...


Lakes, pools can have various shorelines, depending on the environment, that can range from flat beach-like shores to steep (vulcanic) trenches. It's hard to validate if it's a lake based on shoreline characteristics.

Anyhow, I hope Mars Express drops a visit soon over the region too.

PS,
another image, that *might* indicate a lake:

http://www.geocities.com/cuboctahedron2004/lakes3.jpg
(strip available at http://www.msss.com/moc_gallery/m07_m12/images/M09/M0902042.html)

lek
2004-Apr-23, 06:04 PM
If you see the "pond" as black without detail, maybe you should adjust your monitor a bit ;)

Irishman
2004-Apr-23, 06:36 PM
Very interesting. That first one does look like water, or wet dirt. It does follow the contour and look like an equipotential surface. This deserves a closer look.

TheGalaxyTrio
2004-Apr-23, 06:48 PM
It's oil! :o

Quick! Call Haliburton!

We might just get a manned mission to Mars yet! :)

ToSeek
2004-Apr-23, 06:48 PM
Increasing the brightness and contrast brings out some textures that makes it look less like a lake and more like something geological:

http://members.wap.org/kevin.parker/images/lakehicontrast.jpg

Tom Ames
2004-Apr-23, 06:52 PM
That's a very interesting image. Not only does it look like a lake, but it looks as if there's a stream feeding into it. Do any of the Mars orbiters have the equipment to determine if that really is water?

What's the resolution of the laser altimeter? It seems like that would go a long way towards determining if this was a lake.

lek
2004-Apr-23, 06:53 PM
Of course! the old oil in a crater trick! doh!

cuboctahedron
2004-Apr-23, 06:56 PM
Increasing the brightness and contrast brings out some textures that makes it look less like a lake and more like something geological:

I have to disagree; water has a degree of transparancy, so what you might see are the features of the lake-floor. If it were crude-oil for example than it would remain black. You can clearly see a basin now.

01101001
2004-Apr-23, 06:57 PM
I find it curious that the margins of the dark region extending from the crater edge to the "lake" seem to be parallel to many of the numerous dust-devil tracks. That makes me think the dark material was moved by the prevailing winds -- though from or to the crater edge, I cannot tell. Which way do the winds blow there?

There sure seems to be a channel entering on the left end of the lake-like area. That could ell be ancient, though, and perhaps we are now see dark dust filling in a low spot in a former lake.

I'd sure like it to be a lake, though. Or at least a big hunk of ice.

cuboctahedron
2004-Apr-23, 07:02 PM
we are now see dark dust filling in a low spot in a former lake.

If it were dark dust,wouldn't wind at least spread some of the material in it's surroundings? The boundary is to sharp.

Glom
2004-Apr-23, 07:08 PM
cuboctahedron, you have an interesting point amount ToSeek's analysis. I was going to suggest it could be a Lunar style mare.

lek
2004-Apr-23, 07:17 PM
Theres the darker line following the "coastline" in the bottom of the "pond"... bottom detail caused by older coastline?
Fo for a lake it couldnt be very deep, and from the darkness of the bottom it looks like its shallower in the middle areas...

Squink
2004-Apr-23, 10:23 PM
Where's the steam plume from the boiling pool of water?
Now ice, that's a possibility.

ToSeek
2004-Apr-23, 11:10 PM
I did a histogram stretch and brought out what looks like some uneven terrain:

http://members.wap.org/kevin.parker/images/20040422aStretched.jpg

But it would be nice to get a better image to be able to decide for sure.

JonClarke
2004-Apr-23, 11:17 PM
If the ribbed rim on the lower side is of a steep face it could either be a large black sand dune or a lobe of black lava. I would prefer the dune myself.

Jon

RBG
2004-Apr-24, 12:19 AM
How are those photographic strips put together?

Do the original photo edges happen to butt up exactly to one another or did the originals overlap one another as I would think is the case at one point? If they overlap then the actual overlap sections would form a stereo pair as the satellite shot while continuing to orbit.

That stereo pair section then might show whether the feature is concave (like a lake you can see into) or convex (like a dune, which I think I am seeing).

Might it be possible to create an intentional stereo pair with the same satellite on another pass?

RBG

Tom Ames
2004-Apr-25, 03:30 AM
Oliver Morton (http://mainlymartian.blogs.com/semijournal/) discusses this crater on his blog.

cuboctahedron
2004-Apr-25, 10:52 AM
There are many indications of current surface-water on Mars(see example links provided below).

"MOC Images Suggest Recent Sources of Liquid Water on Mars"
http://www.msss.com/mars_images/moc/june2000/

http://www.msss.com/mars_images/moc/june2000/sp_pit/sp_pit_i2.jpg
"NASA unveils evidence of liquid water on Mars"
http://www.cnn.com/2000/TECH/space/06/22/mars.water.01/index.html
"Report: Water springs found on Mars"
http://www.cnn.com/2000/TECH/space/06/21/mars.water/
http://www.cnn.com/2000/TECH/space/06/21/mars.water/story.mars.crater.jpg

Also:last fall a study about water evaporation on mars done by Arkansas-Oklahoma Center for Space and Planetary Sciences states:

...suggest that even under worst case scenarios, where wind is maximizing evaporation, evaporation rates on Mars are quite low." This implies that surface water could indeed exist, or have existed recently, under the given conditions on Mars
http://www.uark.edu/misc/csaps/News/

I understand that one has te be careful when claiming issues regarding surface water, however I can't comprehend that subjects about liquid water tends to be categorized as 'against the mainstream' and that it is saver to say that any occurance related to possible water must ressemble something like "hey, that must be dust or some unknown natural process; water is surely unlikely", making one less vulnerable in debate.
I am not saying such conservatism is right/wrong, but I think it is incorrect when some thesis (e.g. 'no current liquid water on Mars') transforms itself over time into a sort of doctrine, making it more difficult for new perceptions or proposals to alter the initial thesis.

Kaptain K
2004-Apr-25, 02:46 PM
cuboctahedron,

From the phase diagram of water:

http://www.lsbu.ac.uk/water/phase.html

It can be seen that liquid water cannot exist at the pressure found on Mars. It either boils or freezes, depending on the temperature.

cuboctahedron
2004-Apr-25, 02:50 PM
It can be seen that liquid water cannot exist at the pressure found on Mars. It either boils or freezes, depending on the temperature.
If so, The Arkansas-Oklahoma Center for Space and Planetary Sciences must have it all wrong.

I have to read through your link first though :) ., but for a quick response:

I think there are two occasions in which fluid water can form lakes, with respect to the graph mentioned:

- water coming from the soil might be a hot-spring
- temperatures on Mars itself are sometimes not as cold as one might think: http://emma.la.asu.edu/tdaydaily.gif .(note that temperatures here are in Celcius)

In both occassions liquid water on Mars, will probably get coated with an ice layer on top thus preventing severe vapor. Since the ice coat would than vaporize it would yet protect the liquid water lying below, and at the same time vapored ice would get refreshed from the liquid water, replacing the vapored icelayer.

As long as the supply of water exceeds the vaporization, it will remain a lake.

ToSeek
2004-Apr-25, 04:19 PM
It can be seen that liquid water cannot exist at the pressure found on Mars. It either boils or freezes, depending on the temperature.
If so, The Arkansas-Oklahoma Center for Space and Planetary Sciences must have it all wrong.

I have to read through your link first though :) ., but for a quick response:

I think there are two occasions in which fluid water can form lakes, with respect to the graph mentioned:

- water coming from the soil might be a hot-spring
- temperatures on Mars itself are sometimes not as cold as one might think: http://emma.la.asu.edu/tdaydaily.gif .(note that temperatures here are in Celcius)



3. It's not pure water but salt water (brine), which has a different phase diagram from pure water that is more tolerant of cold temperatures.

JonClarke
2004-Apr-25, 10:40 PM
I must say Capt K's phase diagram is very odd. I have never seen the triple point of water given as a decimal of megapascals before.

There is a lot of mythology about the stability of water on the surface of Large areas of Mars are above the triple point of water at least briefly for much of the year. The triple point of water is (with a little bit of rounding) 6 millbars and 0.01 degrees. the average surface pressure of mars is 7 millbars and the equitorial regions ground reach 20 degrees. The problem is that at this pressure the stablity field eith respect to temperature is very narrow.

However, dissolved acids and salts will greatly widen the stability field. with respect to temperature. Surafce water in analogous environments on earth, cold or high deserts, is almpost always quite saline.

Jon

Kaptain K
2004-Apr-26, 07:42 AM
D'oh! I forgot about the "salt effect". My bad! :oops:

Irishman
2004-Apr-26, 08:48 PM
Following a link to a link to a link (Oliver Morton blog to Lori Fenton pages to Journal article on Aeolian Processes in Proctor Crater on Mars article):
http://www.gps.caltech.edu/~lori/pdf/2002JE002015.pdf

Nice big pdf article on Proctor Crater. It very strongly resembles the image we are discussing - big dark spot in the bottom of a large crater that strongly resembles water. The dark spot is clearly sand. The paper goes on at length studying the crater and formation of the surface texture of the sand dunes in the dark crater. My layman's summary is that the sand has accummulated in the crater due to the convergence of winds, and the sand cannot leave. It has been stirred around for some time, and is layered with light colored sand. This has generated a texturing, which that paper discusses in detail.

The paper goes on to talk about dust devil trails and seasonal ice deposits and such, but the conclusion on the big dark patch is that it is sand. Numerous thermal images conclude it matches the properties of sand. MOLA mapping shows texture.

So I am reasonably certain the feature we are discussing is similar. Sorry, not water, but sand. Basaltic sand.

RGClark
2004-Apr-27, 12:25 PM
cuboctahedron,

From the phase diagram of water:

http://www.lsbu.ac.uk/water/phase.html

It can be seen that liquid water cannot exist at the pressure found on Mars. It either boils or freezes, depending on the temperature.

Your phase diagram is oriented towards higher pressures so doesn't show clearly the situation at the lower pressures that are on Mars. This page shows it more clearly:

Triple Point
http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/triplpt.html

Since the pressures on Mars can reach above 10 mbars or .01 atm at some sites, there are locations on Mars where liquid water can exist in liquid form.


Bob Clark

http://www.sv.vt.edu/classes/MSE2094_NoteBook/96ClassProj/examples/trip_pt1.jpg

Glom
2004-Apr-27, 01:09 PM
But would it be like that long enough for a lake to form? At best, you might get a few sweaty rocks.

Kaptain K
2004-Apr-27, 06:52 PM
RGClark,

Yes, that is a better phase diagram for our purposes. Thanks!

While it is true that there are times and places on Mars where liquid water could exist, the vapor pressure would be very close to the ambient atmospheric pressure. The water might not boil, but it would evaporate extremely quickly. In other words, while water could collect in some places, it would quickly evaporate and the evaporation would cool it to the point where the rest would freeze. The ice that formed would also sublimate quickly, so I doubt that there is any surface water (or ice, outside of the poles) on Mars.

cuboctahedron
2004-Apr-27, 08:09 PM
Perhaps another interesting read:

http://www.biospherics.com/Mars/spie2003/SPIE_2003_Paper_GVL_files/image002.gif

Titled:"Odyssey gives evidence for liquid water on Mars"
http://www.biospherics.com/Mars/spie2003/SPIE_2003_Paper_GVL.htm