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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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, 11:25 PM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
Quite- we''re dancing around a tiny tiny wedge at the low pressure end of the liquid part of the H2O phase diagram. Even with dramatic salt content, that end of the diagram doesn't change much.
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Oct 1 2012, 01:36 AM
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Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
Quite- we''re dancing around a tiny tiny wedge at the low pressure end of the liquid part of the H2O phase diagram. Even with dramatic salt content, that end of the diagram doesn't change much. Are you looking at a phase diagram designed for engineers ( most of them are as is the one udolien is using). If so the area of interest to atmospheric scientist will always be a "tiny tiny wedge". On one designed for Martian use the "tiny wedge" will occupy a whole page. |
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Oct 1 2012, 04:13 AM
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Founder Group: Chairman Posts: 14434 Joined: 8-February 04 Member No.: 1 |
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Oct 1 2012, 05:46 PM
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Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
Yes it would - and on that page you would see that at these very low pressures, the temperature difference between melting and boiling is very small. Yes The temperatures and pressures we are used to dealing with on earth in engineering, meteorology, you name it,are rarely near the triple point of water. But on Mars we have an entire PLANET and atmosphere which is never very far from the triple point of H20. Small changes in conditions near the triple point can have major effects. I would imagine future residents of mars would see H20 behave in ways that would seem alien to us. Their very existence might depend on understanding how H20 behaves under Martian conditions. |
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