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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Aug 16 2013, 09:17 PM
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Member Group: Members Posts: 105 Joined: 13-July 05 From: The Hague, NL Member No.: 434 |
The dotted line at 32 F is too pessimistic when you're thinking about liquid water on Mars. A reasonable quantity of dissolved (soluble) salts would easily drop the freezing point to 25 F or lower, which brings most of the measured temps "above the line".
But pls. bear in mind that all the mentioned triple point- and other liq-vap data for water are measured in what's called a "closed system", i.e. 100% water inside a cylinder with a moving piston. An equivalent closed system at Mars would have to be underground. At the surface of Mars we have an open system with such an extremely low partial pressure of water (%water vapor in Mars atmosphere * abs. pressure at the surface of Mars) that we're nowhere near liq/vap equilibrium. Any water pushed to the surface of Mars would "explode" into vapor. |
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