Water On Mars-- Take 3

[PAW]

Thanks, Norval, for the reply to "Water On Mars- Take 2."
All I could find was that the atmosphereic pressure on Mars is from 3 to 9 millibars, compared with the 1000 millibars on Earth.
So my question remains; Is the atmospheric pressure on Mars high enough to sustain liquid water, or would any H2O there be only in the form of vapor which could only frost into ice crystals and then sublime back into vapor under the right temperature conditions, with no liquid stage.
I'm surprised I'm not getting more replies here.
The claim is that flowing liquid water is responsible for some of the recent and ancient features we're seeing on Mars. Yet what I was taught in physics, and experiments I've done in my science classroom, seem to indicate that liquid water couldn't exist on the Martian surface.
Is there an astronomer or physicist out there who could show me where I've gone wrong in my thinking on this?

Patrick

[astro_uk]

My understanding of the situation is that the atmospheric pressure on Mars is not enough to support long lived liquid water. In the Nasa briefing they mentioned that the water (if thats what it is) would be boiling as it flowed down the slope, even though the temperature would be far below 100C.

As I understand it, the picture that is being claimed is that the water was locked up in subsurface ice, until some event lead to a very rapid heating, probably some sort of volcanic activity. The water then burst to the surface where it quickly boiled off, leaving any minerals dissolved in it behind.

The point being that the whole process is very rapid, at least the bit where the water is exposed to the atmosphere, so it can exist for a short time as a liquid, the outer layers boil off as the water moves. Im not sure what effect any dissolved minerals would have on the whole process though.

[ckam]

according to http://nova.stanford.edu/projects/mgs/p ... 40415.html martian atmosphere has roughly 5.5 millibars (= 0.16 in hg) pressure and -33 celsius temperature at the sea level and -19.7 at the surface. according to http://www.csgnetwork.com/h2oboil2calc.html this pressure corresponds to 69.384 celsius for boiling temperature. hence, no problems with liquid water

we can cross-verify it http://www.iapws.org/faq1/boil.htm : 5.5 millibars = 0.00055 MPa, so it lands near 0.000 612 MPa in the table, which gives 0.01 celsius. not 69 degrees, but not -33/-19.7 also

http://en.wikipedia.org/wiki/Vapor_pres ... r_pressure is also helpfull in providing a formula for boiling temperature of water, for 550 Pa it gives 100 + 0.0002772 * (550 - 101000) -1.24e-9 * (550-101000) * (550-101000) = 59,6434089 celsius. a bit closer to 69 degrees, huh?

while at wikipedia, it is also good idea to check martian numbers at http://en.wikipedia.org/wiki/Mars#Atmosphere :

the atmospheric pressure on the surface varies from around 30 Pa (0.03 kPa) on Olympus Mons to over 1155 Pa (1.155 kPa) in the depths of Hellas Planitia, with a mean surface level pressure of 600 Pa (0.6 kPa)... Martian surface temperatures vary from lows of approximately –140 °C (−220 °F) during the polar winters to highs of up to 20 °C (70 °F) in summers

now 20 degrees are a bit more frightening

p.s.: any good reason to make three separate threads for this?

edit: I edited this post few times and probably will again so don't quote me. edit 2: okay im more or less done in this investigation. without data about pressure/temperature in that crater it can hardly been said more.

[ckam]

here's more on subject.

[PAW]

Thank you all for taking the time to reply.
Now all I need is the time to go through the references you all gave me!

I'll share this information with science teachers and scientists I know here in Santa Cruz.
Thanks again...

Patrick