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Ian Goddard
2004-Jan-15, 07:42 AM
An image from Mars Global Surveyor in orbit above Mars:

http://fire.prohosting.com/cleoger/marscolors/dome_on_mars.jpg

The crater must be very large. Does there appear to be a perfectly spherical object in the crater? Has this image been discussed before? The site hosting that copy of the image acquired it from here:

Mars Global Surveyor Image Collection
http://ida.wr.usgs.gov/fullres/divided/m15012/m1501228a.jpg
http://ida.wr.usgs.gov/html/m15012/m1501228.html

The original is exactly the same but includes a larger area. In some regional images there are some slightly similar features, but none as notable as the feature above. What are we looking at?

glen chapman
2004-Jan-15, 08:09 AM
Yeah back in 2000 under very mysterious circumstance Greg Norman lost his ball on the 17th at Castle Hill during the Open - me thinks they found the ball. Bloody long hit for a 3 wood though.

milli360
2004-Jan-15, 09:47 AM
The crater must be very large. Does there appear to be a perfectly spherical object in the crater? Has this image been discussed before? The site hosting that copy of the image acquired it from here:

Mars Global Surveyor Image Collection
http://ida.wr.usgs.gov/fullres/divided/m15012/m1501228a.jpg
Circular? It looks more like a nose to me. :)

AstroCreep
2004-Jan-15, 02:24 PM
Wow, Disney is opening a new Epcot Mars! :lol:

LTC8K6
2004-Jan-15, 02:33 PM
Perfectly spherical for various wide definitions of "spherical". :)

Amadeus
2004-Jan-15, 03:08 PM
sure its a bump? looks like a volcano with the crator on top

Archer17
2004-Jan-15, 03:32 PM
I just think this is what you call an "unusual-looking crater." There appear to be others in the Acidalia Planitia region as well, along with adjacent "tubes" that were discussed here a few months ago. As you can imagine, this is making the woowoo rounds as a cursory search revealed. Maybe someone here with better geological/crater formation knowledge can add something here but if I had to venture a guess I'd say something bubbled up from the crater surface after an impact. The fact is, if you look hard enough, there is always going to be unusual looking craters, "tubes," "trees" etc .. the woowoos even found a Martian equivalent of Mt Rushmore! With all the recent talk of coverups involving color pics and whatnot, I wonder how the woowoos can reconcile the release of pictures showing "artificial domes" in craters. It seems they invoke the coverup angle only when it suits them.

HAVOC451
2004-Jan-15, 03:44 PM
Couldn't it just be the remains of the rock that made the crater?

Ian Goddard
2004-Jan-15, 04:24 PM
I just think this is what you call an "unusual-looking crater." There appear to be others in the Acidalia Planitia region as well, along with adjacent "tubes" that were discussed here a few months ago. As you can imagine, this is making the woowoo rounds as a cursory search revealed. Maybe someone here with better geological/crater formation knowledge can add something here but if I had to venture a guess I'd say something bubbled up from the crater surface after an impact.
Right, as I noted there are similar features in the region. Here (http://ida.wr.usgs.gov/fullres/divided/m15012/m1501228e.jpg) for example in the upper right-hand corner and lower center are two somewhat similar formations apparently also in craters which tends to suggest some kind of emergent phenomenon, ie, perhaps heated by an impact some kind of matter bubbles up in single big bubbles from under the surface. The one seen above is most remarkable, and despite someone's saying "Perfectly spherical for various wide definitions of 'spherical'," it does appear to perfectly spherical as per standard definition.

milli360
2004-Jan-15, 04:26 PM
Most craters have central peaks, formed as the liquified material rebounds and solidifies, just not as large as this one, relatively.

milli360
2004-Jan-15, 04:40 PM
The one seen above is most remarkable, and despite someone's saying "Perfectly spherical for various wide definitions of 'spherical'," it does appear to perfectly spherical as per standard definition.
The one I'm looking at seems flatter on one side.

ToSeek
2004-Jan-15, 04:43 PM
A bunch of the craters in the original MGS image have mounds in the middle. They look like some sort of dunes to me, as do the "tubes".

Ian Goddard
2004-Jan-15, 05:12 PM
The one I'm looking at seems flatter on one side.
Yeah, the one in the center here (http://ida.wr.usgs.gov/fullres/divided/m15012/m1501228a.jpg), which is the one "perfect one," seems to be slightly covered on its dark side by soil falling on it from the crater wall. Unfortunately the site hosting the image at the top of this thread seems unstable. So anyone following this, click on the link in this reply and make sure you're not looking at the a browser-reduced version.

What's curious about this is that if we consider an artificial hypothesis, then the object's origin could be anywhere in the universe, eventually crashing into Mars. However, given the similarity to regional features, the weight of evidence favors natural formation. But to the deeper matter of analytical philosophy: when viewing alien terrains one has to question what are the criteria for entertaining artificial hypotheses? Because we are looking at places where the rules of formation are to some unknown degree outside our experience, there are no clearly defined "artificiality criteria." Therefore, such hypotheses about observed formations are arguably categorically foolish.

Amadeus
2004-Jan-15, 05:13 PM
AHA! I think i'ved got the answer.

Ok picture this.....

A crater is formed.
Sand piles up inside over time.
also over time wind blows accross the crater from all dirctions
Because of line of sight the edges will be blown away but the centre remains intact. because the opposit crater wall will block the wind.

Leave for a few thousand years and hey presto one mound inside a crater!

Gmann
2004-Jan-15, 06:51 PM
http://marsrovers.jpl.nasa.gov/gallery/press/spirit/20040106a/PIA05003.jpg

I'm surprised that the woo-woo's haven't jumped all over this one yet. there is a drain pipe looking thing in the lower left corner, and about 4 inches (on your screen) to the right of center, a cylinder. These are curious, but I'm not ready to believe that a Martian top fuel dragster blew it's engine near an old public restroom.

Ian Goddard
2004-Jan-15, 07:06 PM
Here's a collage I assembled of similar geological features in the Acidalia region of Mars (http://ida.wr.usgs.gov/html/m15012/m1501228.html).

http://users.erols.com/igoddard/acidalia.jpg

The "perfect sphere" is in the upper left image. Fascinating formations!

aurora
2004-Jan-15, 11:35 PM
Those really are interesting.

I wonder if they are impact craters, but an impact into some kind of viscous material -- maybe frozen terrain? which partially melted on impact.

It would be fun playing with various materials to see if there is some way to make an impact look like that.

JonClarke
2004-Jan-15, 11:48 PM
There is no scale on the swath, but calculating from the pixel size the crater is ~450 m in diameter. No that large. Like all young small craters it will be bowl shaped in section, therefore any deposit with in it will be more or less circular.

Sand-laden air blowing across the crater will deaccelerate and drop sand in the middle, building up a mound, in this case ~130 X ~120 m. There are three small traverse dunes on the surface with a spacing of ~10 m.

Whether sand builds up on the windward, leeward or within the dune will depend on the wind velocity and the size of sand particles. Examples of all three can be found on earth and mars

Jon

freddo
2004-Jan-15, 11:57 PM
I have to agree with JonClarke here... If it were impacta, you would expect the deposit to be centrally located more often. Look at Ian Goddard's collage, you can see the mounds in the middle are positioned off centre essentially without exception - which leans me toward an aeolian origin.

Archer17
2004-Jan-16, 01:17 AM
I have to agree with JonClarke here... If it were impacta, you would expect the deposit to be centrally located more often. Look at Ian Goddard's collage, you can see the mounds in the middle are positioned off centre essentially without exception - which leans me toward an aeolian origin.That's a good point. During my earlier search of Acidalia Planitia anomalies I came across references to a sandstorm in that region which obviously indicates wind and I totally ignored it for some reason. #-o BTW, thanks to you freddo, I now know what "aeolian" means. :wink:

Edited twice - once for spelling, another time to properly humble myself :wink:

Ian Goddard
2004-Jan-16, 01:18 AM
I wonder if they are impact craters, but an impact into some kind of viscous material -- maybe frozen terrain? which partially melted on impact.
Yeah, maybe a slush-like surface so soft the meteorites did not disintegrate. Maybe the off-center location of most of them is a kind of deflection that occurred. Everyone's offered good ideas. Amedas' and Jon Clarke's sand-dune hypothesis is attractive, especially in light of the Martian dunes (http://www.space.com/imageoftheday/image_of_day_030731.html) we discussed in this thread (http://www.badastronomy.com/phpBB/viewtopic.php?t=10095&highlight=goddard+dunes) that match crescentic dunes on Earth. Those weird Martian dunes (http://a52.g.akamaitech.net/f/52/827/1d/www.space.com/images/mars_cookies_030731_04.jpg) are so spherical I think that could be the leading hypothesis in this case.

But an oddity is that there appears to be linear stripes across the rounded formations seen in the first two images (upper left to right). I'm not sure if the sand-dune hypothesis can explain those apparent features. It's interesting to note that land formations in the region also have unusual striping, suggesting some wider regional geological cause for these nested spherical formations.

freddo
2004-Jan-16, 01:44 AM
BTW, thanks to you freddo, I now know what "aeolian" means.
What can I say - I'm a walking thesaurus. :lol:


But an oddity is that there appears to be linear stripes across the rounded formations seen in the first two images (upper left to right). I'm not sure if the sand-dune hypothesis can explain those apparent features. It's interesting to note that land formations in the region also have unusual striping, suggesting some wider regional geological cause for these nested spherical formations.

Why doesn't it explain it? Consider it this way. For a ridiculous amount of time, the only thing shaping Mars' terrian (aside from impacts) is the wind. It's still shaping Mars today. Consider that the mounds themselves may have taken up more or less permanent residence inside the craters once they were formed. Essentially the main body - the mound is not going anywhere. However, there's going to come a time when there's too much material to exist in the lee of the crater, or the prevalent weather pattern affects the top layer.
These linear stripes look a whole lot like rippling dunes, just on a smaller scale when viewed in the context of the actual mound. You'll note (referring again to your collage) that these ripples only seem to occur in the deeper craters - where the higher ridges are likely to break up windflow more dramatically.

Ian Goddard
2004-Jan-16, 09:32 PM
These linear stripes look a whole lot like rippling dunes, just on a smaller scale when viewed in the context of the actual mound.
That's a really good hypothesis! Some Martian soil, or sand, seems to have a cohesive quality that allows it to hold together better than dry soil, or sand, on Earth. The cohesive quality of the airbag-disrupted Martian soil was noted both in this thread (http://www.badastronomy.com/phpBB/viewtopic.php?t=10413) and then by a NASA scientist (see my reply in that thread). While the scientist observes that soil around the Pathfinder and Viking landing sites did not have this cohesive quality, perhaps it's somewhat widespread and might allow sand to be formed by the winds into shapes that would otherwise fall apart.

The cohesive quality of some Martian soil reminds me of Moon soil, such as seen in the famous footprint photo (http://nssdc.gsfc.nasa.gov/imgcat/html/object_page/a11_h_40_5878.html). It might be because the soil particles are very ragged-edged broken fragments that were micro-ejecta from meteorite impacts. Dry smooth-edged sand like we find on Earth when pushed into a mound falls apart, or spreads out, since the particles roll over each other. But with rough, jagged edges, particles would tend to stick together, holding the forms into which forces shaped them. In this light, the mud-like character of the Martian soil around the Spirit may mean that sand was deposited long after any water evaporated, since the presence of water might smooth out particles.

kucharek
2004-Jan-16, 09:38 PM
Well, didn't Al Shepard said, "It goes miles and miles and miles..."

;-)

Harald

DJ
2004-Jan-16, 10:17 PM
martian armadillo in his burrow [crater]

Rift
2004-Jan-16, 11:16 PM
The kooks have discovered it....

http://www.xfacts.com/spirit2004/index.htm

](*,)

On the other hand, the soil may in fact be acting like mud... http://www.space.com/missionlaunches/spirit_gusev_040116.html

I love it when nature is stranger then even the kooks can imagine.

Ian Goddard
2004-Jan-17, 07:22 AM
The kooks have discovered it....

http://www.xfacts.com/spirit2004/index.htm
I expect it will get more attention. In the meantime, we've assembled supporting argumentation in this thread for a causal mechanism of the Martian "golf ball" (http://users.erols.com/igoddard/acidalia.jpg): wind-formed sand dunes similar to other dunes on Mars (http://www.space.com/images/mars_cookies_030731_04.jpg) and consistent with observed cohesive characteristics of Martian soil.

While the suggestion at the site you cite that NASA may be altering the color of Rover images to hide the "golf ball" is indeed patently ludicrous, it's worth noting that I don't think we should see artificiality hypotheses per se as inherently ludicrous. SETI searches are looking for signs of artificiality, and there have been times during such searches that artificial hypotheses were raised. When the first pulsar was discovered in 1967 astronomers were so surprised they raised the hypothesis that it was an alien beacon. I don't think that was inappropriate. But in all those cases artificiality hypotheses were abandoned under the constraints of falsification criteria. Discontent arises in us when others do not subject themselves to such constraints.

Archer17
2004-Jan-17, 03:59 PM
I think one of the things woowoos overlook when making claims of a coverup is that legitimate artificial structures would be a boon to NASA and spark a renewed interest in manned Mars exploration. IMO it would not be in NASA's, or in extension, the government's best interests to cover anything like this up. At best, this "coverup" would only be temporary anyway as other countries will go there down the road.

Hat Monster
2004-Jan-17, 05:16 PM
Looks more like a slightly raised area of sand dunes to me. The shadowing is not right for anything spherical. Sand dunes exist and are common on mars, especially within craters.

H@

Sticks
2004-Jan-17, 07:27 PM
I think this image from Spirit is highly suspect :lol:
http://www.gsne03768.pwp.blueyonder.co.uk/images/mars-franchise.gif

kucharek
2004-Jan-19, 12:28 PM
martian armadillo in his burrow [crater]

You mean one like that (http://www.hq.nasa.gov/alsj/a14/ap14-KSC-70P-498.jpg)?
Then again, it's an Al Shepard ploy....

Harald

SiriMurthy
2004-Jan-19, 06:10 PM
Martians playing Golf. http://ida.wr.usgs.gov/fullres/divided/m15012/m1501228a.jpg looks like a Golf ball to me. :lol:

Thomas Kirby
2004-Nov-30, 01:39 AM
Say what you like, people, but that is the only image I have ever seen that looked convincingly like an artificial structure of any kind on Mars with adequate detail and without resorting to wishful thinking. It made me wonder if someone's secret mission from Earth was lost that way, like one of the old ideas for a balloon or spherical landing vehicle.

lyford
2004-Nov-30, 02:18 AM
Say what you like, people, but that is the only image I have ever seen that looked convincingly like an artificial structure of any kind on Mars with adequate detail and without resorting to wishful thinking. It made me wonder if someone's secret mission from Earth was lost that way, like one of the old ideas for a balloon or spherical landing vehicle.
Geodesic Domes? Giant Golf Balls?
http://users.erols.com/igoddard/acidalia.jpg
Personally, I think dunes are a more likely interpretation, a la Endurance. (http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040602a.html)
http://marsrovers.jpl.nasa.gov/gallery/press/opportunity/20040602a/12-WC-01-endurance-B127R1_br.jpg
So nice to have "ground confirmation" of orbital imagery, innit?

Thomas Kirby
2004-Nov-30, 04:31 AM
I would have to say that the round and roundish objects are actual hard objects of some kind. Could a few small asteroids have actually made "soft" landings? Thin atmosphere, deep sand, low gravity, and all tracks wiped away by the wind. Maybe a few of them hit the atmosphere just right to soak up enough of their kinetic energy to keep them from shattering. It would be a very unlikely event but there are millions of events to choose from.

Ian Goddard
2004-Nov-30, 05:04 PM
I would have to say that the round and roundish objects are actual hard objects of some kind. Could a few small asteroids have actually made "soft" landings? Thin atmosphere, deep sand, low gravity, and all tracks wiped away by the wind. Maybe a few of them hit the atmosphere just right to soak up enough of their kinetic energy to keep them from shattering. It would be a very unlikely event but there are millions of events to choose from.
These natural Martian dunes (http://www.space.com/images/mars_cookies_030731_04.jpg) have very similar characteristics, and the rovers have shown that Martian sand can be very cohesive. Also, I believe any asteroid would strike a planet at least at the escape velocity of that planet, which would be far too fast for a soft landing.

lyford
2004-Nov-30, 05:32 PM
These natural Martian dunes (http://www.space.com/images/mars_cookies_030731_04.jpg) have very similar characteristics, and the rovers have shown that Martian sand can be very cohesive
I am sorry, but that image is obviously a PacMan convention. You are mistaken. :lol: If we sent the rovers in I am afraid they would get gobbled up!

I notice the space.com caption implies Fortune Cookies - pareidolia strike again!

BTW, does anyone know of a site that compares Earthly geologic features from orbit with pics from the ground? I have googled a bit in the past looking for ammo deal with the Cydonia folks, but never found one site that had everything that I was looking for... The Remote Sensing Tutorial (http://rst.gsfc.nasa.gov/Front/tofc.html) is great, but I am looking for an "upstairs/downstairs" gallery comparing features as they look from the ground to from above...

lyford
2004-Dec-01, 06:49 PM
More neat dune fillings.... (http://www.msss.com/mars_images/moc/2004/11/27/)

http://www.msss.com/mars_images/moc/2004/11/27/2004.11.27.R2100357.medium.jpg

It's worth seeing the detail in the large image (http://www.msss.com/mars_images/moc/2004/11/27/2004.11.27.R2100357.gif), which reveals some neat dune effects in all the craters. Since you see the exposed rock, you can imagine the wind blowing all the darker sand and dust into the craters, forming rippling patterns - they look like swimming pools even!

Maybe we can get Opportunity to drive north after Victoria? :wink: Though I hope the "etched terrain" may yield some awesome similiar effects...

frogesque
2004-Dec-01, 07:31 PM
lyford

That image is the real cat's whiskers! Why does anyone need to look for goofballs, faces or manipulated image artifats on Mars when there are fantastic picture like the one you referenced above. A pristine, sandy Martian desert, unknowing and uncaring yet able to inspire such awe in us.

Just to emphasise the point - who said black and white photography was dead?! Absolutely magnificent =D>

Thomas Kirby
2004-Dec-01, 08:52 PM
The three larger craters in that photograph are going to turn out to contain liquid water when we get around to confirming it. The reason for sand to flatten out like that is because it actually fills a pool of water.

The largest crater has dark areas at the right hand edge that are not consistent with being in shadow. It can be magnified and seen that there is more than one bright object in what appears to be water. The surface of water would look dark unless it reflected sunlight directly back at the camera, but it would illuminate objects near it. This can be seen in the photograph. The cliff edges look as if they are illuminated from below, toward the darker areas. The brightest objects in the largest crater, even in the entire photograph, look as if they are lit by reflection from whatever the dark areas are.

Those don't look like impact craters. They look like sinkholes. There is no material thrown around outside the edges of the craters, no raised rim. The entire area looks like it has been etched by acid. This makes sense if the sedimentary rocks are some kind of carbonate. Any liquid water on Mars would contain a lot of carbon dioxide, which dissolves carbonates.[/img]

Ian Goddard
2004-Dec-02, 02:43 AM
It's worth seeing the detail in the large image (http://www.msss.com/mars_images/moc/2004/11/27/2004.11.27.R2100357.gif), which reveals some neat dune effects in all the craters. Since you see the exposed rock, you can imagine the wind blowing all the darker sand and dust into the craters, forming rippling patterns - they look like swimming pools even!
Awesome! Indeed, many of the intra-crater sand patterns resemble water-surface patterns. Check out these intra-crater sand patterns (http://qt.exploratorium.edu/mars/opportunity/navcam/2004-08-22/1N146479099EFF35B8P0641R0M1.JPG). They remind me of water in a swimming pool, as you observe. Notice also how you can just make out some ripples running along the "golfball dune" seen elsewhere in this thread.

jt-3d
2004-Dec-02, 10:24 AM
The three larger craters in that photograph are going to turn out to contain liquid water when we get around to confirming it. The reason for sand to flatten out like that is because it actually fills a pool of water.


I don't think so. While the bottom crater does indeed give the impression of being a refreshing pool of martian water, Mars is still a giant desert, a desert where the wind blows for months. Blowing sand fills the craters, not water. Once blown in, the only way the sand could get back out is by venturi effect and apparantly the winds are not that strong. If we could get another shot of the same area take later, I'd bet the ripples would be in about the same place thus making it sand.

frogesque
2004-Dec-02, 10:37 AM
The three larger craters in that photograph are going to turn out to contain liquid water when we get around to confirming it. The reason for sand to flatten out like that is because it actually fills a pool of water.


I don't think so. While the bottom crater does indeed give the impression of being a refreshing pool of martian water, Mars is still a giant desert, a desert where the wind blows for months. Blowing sand fills the craters, not water. Once blown in, the only way the sand could get back out is by venturi effect and apparantly the winds are not that strong. If we could get another shot of the same area take later, I'd bet the ripples would be in about the same place thus making it sand.

Agreed, surely, if the wave like patterns were water they wouldn't have the clarity of detail in these images, they would be fogged and smudgy due to the exposure time, kind of like taking a long exposure shot of a waterfall. Also those dunes look massive, I know it's not a 3D veiw but clues from the shadows cast give some indication of their height compared to the shadows cast by the crater walls. 3/8 earth g, ~10mb pressure, a lake fetch of at most a few kilometers and temperature of ~ minus 50C there is no way these could be water waves.

Edit: Thomas Kirby Please ask yourself this question, "If there is so much free water on Mars why do we not see the signature of it in atmospheric analysis?"

At the ambient pressure on Mars, if free water existed it would boil at anything above about plus 10C and create huge cloud plumes we could probably see from Earth with a decent telescope, never mind a high resolution orbiter. We can't see them because there is no surface water there however much wishfull thinking we might indulge in.

Personally I would be delighted if we found Martian water in a 'temperate' zone on Mars and there may yet be a case for a fosilized subteranian aquafed if the pressure from an overlying regolith AND underground Martian temperatures maintain the right conditions for it to be stable. It's what makes the search for water so tantalising but suface conditions will not support long term free water.

Thomas Kirby
2004-Dec-02, 05:06 PM
The field is moving pretty fast. The NASA sites are publishing maps of the estimated amounts of water vapor in different places on Mars now. That signature that you are talking about is there.

http://humbabe.arc.nasa.gov/MarsToday/MarsWater.html

For whatever my opinion is worth, if as this site says there is a fair amount of water trapped in the top few centimeters of soil, there is a lot more underneath. Some of it trickles down. If enough water made it down to raise the water table a millimeter each year on the average, that would be a kilometer's worth after a million years and ten kilometer's worth in ten million years. Plus I think it started out with a pretty good store of water. If you have equatorial seas, it doesn't matter if the atmosphere is lost quickly or slowly. The water is only going to evaporate from those seas until the sand covering it protects it from further evaporation.

I think that the sand is only particularly cohesive when it is damp enough, just like on Earth. If that weren't the case it wouldn't be blowing around the surface or the craters. I think the shape of the waves of the sand looks like the sand is sticking together after it has gathered in the craters. That large picture magnifies pretty well. I have to really doubt any 50 degrees below zero during the day. Cut and paste from the site the large image came from: This image is located near 2.3°N, 2.0°W. For all practical purposes this image is on the Equator. It might get as high as 70 degrees pretty quickly there, and the ground temperature could be a lot hotter than the air temperature. We are also permitted almost 50 degrees Fahrenheit before the water starts boiling away, and it IS boiling at a low vapor pressure, about a hundred times less than on Earth. Even if it has started boiling it will take it time to build up a good head of steam.

Water covered with ice tends to hold heat in the water and regulate its temperature at about the freezing point, sourcing and sinking heat in the heat of fusion of the water. It's very common on Earth to have sub-zero temperatures just a fraction of inch away from liquid water. Even if it goes down to fifty below at night, all of that ice can still thaw during the day. There is a lot of warmth trapped in the wet sand in that crater so it will not freeze quickly at night.

What impresses me most is the biggest, irregularly shaped crater near the top of the picture. Magnify and look along the righthand side. The resolution is about 3km/640 pixels, so it's about 5 meters resolution. The darkest band is where I think the liquid water is. It resolves well enough under magnification to see where we are viewing sand through the water, and reflections from the water illuminating the cliffs. The sand actually vanishes into a darker area. It is impossible for that darker area to be in the shade. The slopes into it are gradual. There are shadows on the other side of the crater that show that the sun is an hour or two short of, or an hour or two past being directly overhead. It's coming in from the left and top of the photograph at a steep angle. The light would shine right down to the bottom of a depression.

The ripples in the sand cut off at the waterline. You can see into the water well enough to see that the sand in the water has flattened out and even where there are ripples, they don't show well. If there is another explanation for the sand suddenly becoming darker (but still visible) in a straight line, and the sand lying much flatter, it would be a fascinating one indeed. I'll say it again. The waves in the sand cut off at the dark band at the base of the cliffs. That dark band is illuminated from nearly directly overhead. There is nothing nearby that can shade those dark areas. The same sand would be in the dark band that is in the rest of the crater floor.

jt-3d
2004-Dec-02, 05:47 PM
I think the dark areas would be wind shadows, places where the wind can't blow directly on the sand and so it can't form the dunes. You can't have dunes without wind thus, no dunes right next to the cliffs. Go ahead and open that spa up there but don't go crying for water shipments when you find out it was all a mirage.

Thomas Kirby
2004-Dec-02, 07:08 PM
The picture is there to look at.

R.A.F.
2004-Dec-02, 08:06 PM
The darkest band is where I think the liquid water is. It resolves well enough under magnification to see where we are viewing sand through the water, and reflections from the water illuminating the cliffs.

You seem to be gleaning more information from this image than is actually there. As frogesque pointed out, the idea of free standing water on Mars is wishful thinking. Yes, planetary scientists have found evidence of past water...and I'm sure that in the past conditions on Mars were different. But this is the present...and observations indicate that Mars is a very cold, very dry place.

Thomas Kirby
2004-Dec-02, 09:32 PM
First, have you zoomed in on the areas I described and looked at them closely?

Second, what is the daytime temperature at the equator of Mars?

Third, no one has proven that freestanding water on the surface of Mars is "wishful thinking."

frogesque
2004-Dec-03, 12:52 AM
First, have you zoomed in on the areas I described and looked at them closely?

No, I have no desire to look at magnified compressed image artifacts


Second, what is the daytime temperature at the equator of Mars?

Third, no one has proven that freestanding water on the surface of Mars is "wishful thinking."

Although I feel the burden of proof is now on you to show that it is possible for liquid water to exist and remain stable on the surface of Mars I have prooved to my own satisfaction that it cannot. I have yet to convert that proof into a suitable form for posting onto this board in a way that is comprehensible to anyone not conversant with the properties and thermodynamics of H2O at low pressure.

In the meantime I refer you to this document Authorised by: Head, Earth Sciences
(http://www.earthsci.unimelb.edu.au/mars/Water.html)

Thomas Kirby
2004-Dec-03, 01:20 AM
It's a .GIF image. There are no compression artifacts. It is a lossless compression algorithm. Water can exist as a liquid at 10 millibars of atmospheric pressure to more than 40 degrees fahrenheit, a fact that is mentioned on the NASA websites. I also left links in the other thread.

The vapor of pressure of water is less than 10 millibars at 40 degrees Fahrenheit, and that alone proves that liquid water can exist on the surface of Mars during parts of the day. The vapor pressure of ice at 32 degrees Fahrenheit is MUCH less than 10 millibars, and that proves that ice is fairly stable at and near the surface. It was NASA's own water site that said there was a lot of water bound up in the top few centimeters of soil.

Your source has entirely failed to look up temperatures and vapor pressures. That makes his statements much less useful because they aren't even backed by information that is readily available.

One thing that I cannot really understand is why someone hasn't already made exhaustive and precise measurements to determine the actual amount of water and water vapor, rather than the amounts predicted by models. Models are worth about the phosphors that they are displayed on, maybe less, until there are actual measurements to go with them. Models that are given without references are worth even less. They certainly do not disprove competing models.

This link (http://adsabs.harvard.edu/cgi-bin/bib_query?2000LPI....31.1509H) is to a fairly authoritative paper that claims that the conditions for liquid water exist on present day Mars, if there were any water there.

Thomas Kirby
2004-Dec-03, 02:49 AM
It also didn't occur to me until just now to use the fact that water that is in contact with a fair amount of ice will stay near the freezing point. Its vapor pressure at that temperature is 4.58 mm of mercury. (http://hyperphysics.phy-astr.gsu.edu/hbase/kinetic/watvap.html) 10 millibars=7.6 millimeters of mercury. Liquid water that has its temperature regulated by ice will not boil at 10 millibars of air pressure. It will also tend to stay pretty chilly because it releases its heat as water vapor even when it is not boiling.


(edited to correct a typo)

frogesque
2004-Dec-03, 04:12 AM
Thomas Kirby I followed your link and have printed it off for study - at first reading it apears to be highly speculative.

Folowing on from where I left off my own case is this:


Second, what is the daytime temperature at the equator of Mars?

Nasa Teacher's Guide Activity 5.1 Today's Temperature on Mars (http://quest.arc.nasa.gov/mars/teachers/tg/program5/5.1.html)


On a warm summer afternoon, near the Martian equator, the surface temperature can occasionally climb to 65° F (18°C). Even a few centimeters above the surface, however, temperatures are lower. And at this same spot, the temperature at sunset will have dropped to below freezing and during the night the thermometer will plunge to more than 100 degrees below zero F. Around Mars' Northern polar cap, during the long winter nights, temperatures can fall to as much as 200 degrees below zero F!


Third, no one has proven that freestanding water on the surface of Mars is "wishful thinking."

Viking Lander Data (http://www-k12.atmos.washington.edu/k12/LFEM-STEP/viking/lander/viking_lander_vcf/node14.html)

Taking the best possible case from Viking Lander 1 (VL1) the maximum surface pressure was 10.2 milibars.

from Chemical Engineering Design and Analysis: An Introduction
T. M. Duncan and J. A. Reimer, Cambridge University Press, 1998.

©Cambridge University Press. Pressure – Temperature Phase diagram of Water (http://www.cheme.cornell.edu/%7Etmd/Graphs/4-6.doc)

and Water Phase Diagram (http://merlin.che.gatech.edu/CHE2110/uploads/16/water_phase_diagram.pdf)

we can see that at a pressure of 10.2mb and a temperature between 0C and 25C that liquid water can in fact exist. Mars’ equatorial temperature can be as high as 18C. Eureka!

Unfortunately this is only half of the story and the half where most people get confused. Martian atmosphere contains some 0.03% by volume (http://www.daviddarling.info/encyclopedia/M/Marsatmos.html) of water vapor so the partial pressure acting on any free body is about 0.003mb and at that partial pressure liquid water cannot exist because it is below the triple point. Providing the ambient temperature is below about –68C (best estimate from the chart, 205K) it will be in the solid (ice) phase and if the temperature rises above –68C it will sublime to the vapor phase. (There is an Earth analogy, on a very cold dry day ice and snow don’t melt during the day but they do shrink. Because the partial pressure of the water vapor in the air is so low the ice sublimes)

During Martian winters there may be some precipitation of frost and just possibly snow in some of the shaded corners of equatorial craters but as soon as the temperature rises that precipitation will vaporize without going through a liquid phase.

Unfortunately I have been unable to find a psycrometric chart based on Martian atmosphere. It would give a much clearer picture of what will happen but I hope the above has convinced you to your satisfaction.

It's 3.30am here and my eyes are dropping out of my head so I do ask everyone to rigously check all my arithmetic.

Thomas Kirby
2004-Dec-03, 05:37 AM
It does not take any partial pressure of water in the atmosphere at all to preclude boiling of the water, which is the condition that I have been testing for. The body of water will evaporate, but how quickly is something that has to be carefully thought out, or preferably measured. If the water is at 32 degrees you have less than 5 millimeters of mercury of pressure, or less than 1 percent of an earth atmosphere of vapor pressure and that is the maximum pressure that the water will be able to exert against any atmosphere or against a vacuum. Were the air saturated with evaporated water then no evaporation would take place at all. Still air would keep more water in because layers of water vapor tend to stay low. This doesn't require that there be visible fog either.

You said:
Unfortunately this is only half of the story and the half where most people get confused. Martian atmosphere contains some 0.03% by volume of water vapor so the partial pressure acting on any free body is about 0.003mb and at that partial pressure liquid water cannot exist because it is below the triple point. Providing the ambient temperature is below about –68C (best estimate from the chart, 205K) it will be in the solid (ice) phase and if the temperature rises above –68C it will sublime to the vapor phase. (There is an Earth analogy, on a very cold dry day ice and snow don’t melt during the day but they do shrink. Because the partial pressure of the water vapor in the air is so low the ice sublimes)
------------------------------------

This doesn't mean that ice will evaporate before it melts. Very thin layers of ice or very light frost could evaporate before they melt, but not heavy frost or a dusting of snow. It probably also isn't simply evaporating away when there are areas where the frost can be photographed from space at 9 am local time and it can be seen in areas that have been sunlit for an hour or more. It most certainly does not mean that if there is water pooled somewhere, that it will evaporate before it thaws. A pot of boiling water puts out vapors at 150 to 100,000 times as fast even when it is just barely boiling, and at that rate it still loses less than an inch in an hour. All your ice has to do is reach the melting point before it all evaporates, and you have liquid water. This is easy even at 10 millibars if you have ice an inch thick, or a pool of water with ice on top.