Mars and Missoula

[rogers_buck]

There was an interesting Nova the other night about the Scablands and lake Missoula. For those not familiar with the topic here is a brief synopsis.<br /><br />Back during the last ice age, glaciers blocked a river a valley in present day Missoula Montanna. Behind the 300 mile wide ice dam a massive lake some 500,000 cubic miles of water formed. The ice dam failed and an epoch flood was unleashed that carved out much of the interesting geology of that region.<br /><br />Now what I found interesting was the mechanism by which the ice dam failed. Apparently, near the bottom of the thick glacier ice under pressure becomes super cooled water and is then forced deep into the glacier through cracks. The motion of the super cooled water through the ice creates friction and releases heat. Eventually, the process thermally and hydraulically undermines the ice dam and it collapses.<br /><br />Now the martian bit. Considering that there is a vast sheet of ice at mars southern pole some 2 miles thick, what part of that dynamic might come into play? Could lower layers of the ice sheet become the source for super cooled liquid water that would heat the entire ice flow as it permeates through its structure? Given the size of the ice flow could it be that there is a critical point where the ice collapses from such internal heating?<br /><br />I guess the ultimate scenario would be that much of mars water would pile up at the pole until it was released by a catastrophic melting. The floods would then swamp the planet and carve out lots of geology. Then, in time, the water would evaporate and be frozen out of the atmosphere at the poles. Eventually, the critical mass of ice would form and the process would repeat after some chaotic trigger.<br />

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Mazula Montanna.<p><hr /></p></p></blockquote><br /><br />Would that be Missoula, Montana? <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[logicize]

I believe that was what he was looking for. It's a pretty cool place, maybe I'll move there someday. <br /><br />I think that idea would explain some of the massive erosion you see on the surface of Mars.<br /><br />I'm not a very good speller either, or grammerist for that matter.

 

[rogers_buck]

My mistake... I'll go fix the thread title at least. (-;<br />

 

[JonClarke]

the Channeled Scabland formed by the overflow of Lake Missoula has been long seen as an analogue for the Martian outflow channels. There is a lot of material available on this, Vic Baker's book "The Channels of Mars" is still the definitive reference.<br /><br />Some web sites include:<br /><br />http://www.ndsu.nodak.edu/instruct/schwert/geosci/g496_columbia_plateau/g495link.htm (lots of links)<br /><br />http://tes.asu.edu/TESNEWS/4_VOL/No_3/ken_jim_1.html<br /><br />http://mpfwww.jpl.nasa.gov/MPF/martianchronicle/martianchron4/martianchron48.html<br /><br />http://www.kidscosmos.org/kid-stuff/mars-trip-scablands.html<br /><br />Jon<br /> <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>

 

[rogers_buck]

Not quite my point. You have really wet pole and signs of massive floods. That is good for the Missoula scenario and pretty obvious. My point wasn't about the flood, it was about the mechanism. If mars wasn't like earth with meandering rivers and glaciers but was more like it is today, how could the flood occur?<br /><br /><br />What I found most interesting was the mechanism by which those ice dams collapse. I had never heard of the phenomena of super cooled water at the bottom of ice dams actually heating the ice as it forces its way to lower pressures. The question I have is what might happen in the martian environment to a huge ice sheet that is being heated from within by its own sheer size? Is it concievable that a 2 mile thick ice pack on mars might collapse and fill the atmosphere with polar CO2, water vapor, and thereby explosively melt the ice pack?<br /><br />Apparently, on earth, those ice dams literally explode when they fail. Mostly due to the water pressure. What would the dynamic be on mars near vacuum for a much, much, larger ice pack?<br /><br /><br />

 

[rogers_buck]

Nice links. Thanks.<br />

 

[spacester]

Hi rogers_buck - it's nice to have a chance to add something to one of your threads, even if only very basic; you have added a lot to my thinking over the years. <br /><br />The pressure at the bottom of the ice pack is going to be approx. given by:<br /><br />P = rho * g * h<br />Where<br />P = Pressure<br />rho = density of the ice<br />g = acceleration due to gravity<br />h = height of the ice pack above the point in question<br /><br />If we assume Earth ice and Mars ice are the same stuff, rho is the same. We know that g on Mars is 0.38 that of g on Earth. Therefore, the pressure under the same height of Martian ice would be 0.38 that of Earth ice. We also could state that to get the same pressure, the height would need to be 1 / 0.38 = 2.63 times on Mars as on Earth.<br /><br />If the two ices have the same mechanical properties (I have no idea how valid this assumption is) then the pressure at depth can be taken as the primary criteria of failure. IOW we can assume that they will fail at the same pressure on each planet.<br /><br />So a 2 mile thick Martian ice pack would, at this simple level of analysis, be the same as a 0.76 mile thick Earth ice pack. That's about 4000 feet or 1220 meter. The Missoula ice dam must have been much less high than that. (?)<br /><br />The atmospheric pressure is much less than the pressure of the ice in both cases, so is basically not a factor here.<br /><br />Of course, things are certainly much more complicated than this simple look-see, but indeed it would appear that a 2-mile thick ice sheet on Mars would have a lot higher internal pressure than the Missoula ice dam.<br /><br />I suspect that geothermal heating from below was a major factor in creating the super cooled water that led to failure. My understanding is that there is no expectation that Mars would have a similar heat source.<br /><br />Also, the geometry would seem to be much different, with the Martian ice gradually thinning as you move away from the pole, whereas the ice dam was a <div class="Discussion_UserSignature"> </div>

 

[JonClarke]

My apologies, I misunderstood.<br /><br />I guess that ice dams are quite possible, especially in some the long incised channels like Uzboi. Failure of ice seals of aquifers is another possibility. <div class="Discussion_UserSignature"> <p><em>Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars</em>  Arthur Clarke</p> </div>