Temperature and pressure at Gale, Suitable (for short periods) for liquid water? |
Temperature and pressure at Gale, Suitable (for short periods) for liquid water? |
Sep 30 2012, 03:23 PM
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#1
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Junior Member Group: Members Posts: 62 Joined: 11-July 11 Member No.: 6058 |
Just a quick query from someone with no background in science. Obviously, MSL has AFAIK not returned evidence of recent (i.e. years/decades) liquid water in its vicinity; however, I was interested by the following graphs:
08.21.2012: First Pressure Readings on Mars http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=4501 08.21.2012: Taking Mars' Temperature http://mars.jpl.nasa.gov/msl/multimedia/images/?ImageID=4502 The first indicates that the pressure between 15 Aug and 18 Aug never dropped below c. 690 millibars; the second shows that, for a period of a couple of hours on 16 Aug, the temperature rose above freezing. If water had been present on the surface, then, would it have been liquid during this brief period? The pressure and temperature seemed to satisfy the conditions for liquid water as I understand them (indeed, the pressure seems to be high enough (just) on a 24-hour basis to allow for the presence of liquid water). Thanks in advance for your opinions (corroborative or not!) on this. |
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Sep 30 2012, 09:47 PM
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Founder Group: Chairman Posts: 14433 Joined: 8-February 04 Member No.: 1 |
It would boil, would it not?
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Sep 30 2012, 11:37 PM
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#3
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Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
It would boil, would it not? As shown in one of my previous post, the surface pressure may be as high as 14mb. At that latitude (40 south) on mars at that season mid day near surface air temperatures are well above freezing. So temperature and pressure are high enough. Rapid evaporative cooling could ice over our glass of ice water in the extreme dryness, even with air temps above freezing. But solar radiation might offset the evaporative cooling. If this happens, our glass of ice water might slowly warm a few degrees before it completely evaporates but because the boiling point might be as high as 10c at 14mb the water would evaporate before it ever warmed to the boiling point. Like I said, it is a fun little thought experiment. Small changes in parameters drastically change the outcome. For instance, if the glass was sitting on black sand dunes (albedo .05) the infrared warmth ( dune temp could easily be 35-40c) might warm the ice water quickly enough for it to begin boiling before it completely evaporates |
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Sep 30 2012, 11:44 PM
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#4
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Junior Member Group: Members Posts: 40 Joined: 29-December 11 Member No.: 6295 |
For instance, if the glass was sitting on black sand dunes (albedo .05) the infrared warmth ( dune temp could easily be 35-40c) might warm the ice water quickly enough for it to begin boiling before it completely evaporates The phase transition under the conditions mentioned would happen directly from ice to gas. It evaporates. There would be no boiling at all. At 40c a liquid phase is impossible at 6-10 mbar air pressure. In my above phase diagram the phase transition would happen from point D to F. No liquid phase at all. Udo -------------------- But to be a lament on the lips of the loved one is glorious, For the prosaic goes toneless to Orcus below. (Friedrich Schiller: Naenie)
Home of marspages.eu and plutoidenpages.eu |
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Oct 1 2012, 12:33 AM
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#5
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Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
The phase transition under the conditions mentioned would happen directly from ice to gas. It evaporates. There would be no boiling at all. At 40c a liquid phase is impossible at 6-10 mbar air pressure. In my above phase diagram the phase transition would happen from point D to F. No liquid phase at all. Udo Note that I am talking about magically placing a glass of ice water ( temp 1c or so) on the surface. Please see earlier post. As I state, the 40c temp I mentioned is the temp of the sand, not the water. Radiative heating from the surrounding sand would probably be more important than conduction thru the bottom of our glass. And I'm not clear on why you are referring to the phase diagram of CO2 in some of your post |
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