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, 04:03 PM
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Junior Member Group: Members Posts: 85 Joined: 5-September 12 Member No.: 6635 |
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. In theory the answer is yes. But the thinking is that the strong evaporative cooling at what is essentially a 0% relative humidity associated with these brief high temperatures would make a liquid state difficult to maintain or achieve. However, imagine placing a pan of water at ground level in sun versus shade (insulated from the ground) at the MSL site. The pan in full noonday sun would still evaporate but solar heating might offset evaporative cooling enough to keep it liquid while it evaporated. Not so in the shade. Note that our pan of water is assumed to have an initial temperature just above freezing because the boiling point on mars even at the bottom of Hellas will never be more than about 5-10c above freezing. This last fact makes it even more difficult to keep liquid water from icing over |
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