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A question here, behaviour of water on Mars
spdf
post May 24 2007, 12:38 AM
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A question here

There are signs that in the past there was liquid water on Mars. So lets assume thats true.
Since the gravity on Mars is much lower than on Earth, so how does water (waves) behave on Mars compared to Earth?
Someone did say, that waves would have been much higher but also much slower. Is this true? Does anyone have an animation where you can see a waive on Earth in comparsion to a wave on Mars?

Thanks
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djellison
post Nov 15 2007, 07:12 PM
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And of course, the fact that water can exist, at some times, in some places - doesn't mean it does. It is a transient thing and would boil away quite easily - thus it would have to be replenished in some way.

Doug
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rlorenz
post Nov 16 2007, 01:47 AM
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QUOTE (djellison @ Nov 15 2007, 02:12 PM) *
And of course, the fact that water can exist, at some times, in some places - doesn't mean it does. It is a transient thing and would boil away quite easily - thus it would have to be replenished in some way.


Good thread. I remember I got asked about this one by NPR when the Mars Gullies story first came out. 'Isnt
Mars too cold for liquid water?' Well, yes, I answered, and Earth is too cold for liquid rock - doesnt mean it
never happens.....

Another data point - when I was at the Mars wind tunnel at NASA Ames doing wave generation experiments,
I noticed they have a big jar of water in the chamber just inside the window to the control room (wind tunnel is open
circuit - inside a large room that gets pumped down). As the pressure drops, the water starts to bump and boil,
but then stops, while still liquid. (i.e. it boils until the evaporative cooling brings the temperature well below
that at which the saturation vapor pressure equals ambient). We had a big tray of water on which we were
hoping to generate waves - we could see on the video link that it bumped once or twice, I guess with bubbles
of dissolved air coming out. Then we turned the airflow on in the hope of making waves at 10mbar or so, and saw
the water glaze over - the enhancement in evaporative cooling by the airflow was enough to freeze it.

Pure water has 6mb vapor pressure at 0 C (and 20mb at 20C - I remember it as 20:20)

When I lived in Arizona, this issue of the metastability of water on Earth's surface was rather evident - spill
water in the kitchen, no problem, it'll dry up by itself in 3 minutes. At the DPS conference in Monterey (2003?)
I raised the question in connection with Titan (known to have 50% or so relative humidity, so where are the
oceans?) - I pointed out that Earth is 60% covered in water, and yet we can hang out laundry to dry. Clearly
this wouldnt work unless the relative humidity were much lower than 100% (because of circulation to higher
altitudes, which dries the air..)

Anyway, it remains a subtle issue. I'd urge people read Mike Hecht's work on the topic (he has a rather
fresh perspective). And I think Titan (where ethane takes the role of salt, in lowering the saturation vapor
pressure of the volatile component in a solution) will be very instructive in comparisons with Mars.

So - Doug's words 'transient' and 'replenished' are key - if the system is out of equilibrium, then lots of
things are possible. And I guess I am learning over the years that disequlibrium isnt that hard to generate...
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Posts in this topic
- spdf   A question here   May 24 2007, 12:38 AM
- - tuvas   This is just a guess, but I would guess waves woul...   May 24 2007, 08:19 PM
- - ugordan   I believe the higher-and-slower waves is the corre...   May 24 2007, 08:44 PM
- - nprev   Another major variable would have been atmospheric...   May 24 2007, 11:17 PM
- - dvandorn   Actually, liquid water on Mars would behave consis...   May 25 2007, 07:50 AM
- - AndyG   ...and add bigger drops. Surface tension will play...   May 25 2007, 08:31 AM
- - nprev   Great story, oDoug! Yeah, I should have bee...   May 25 2007, 11:50 AM
- - Juramike   While there would be no really big tides on a Mart...   May 25 2007, 03:41 PM
- - helvick   On earth the average atmospheric pressure of ~101k...   May 25 2007, 04:52 PM
|- - marsbug   I have a question I've not been able to resolv...   Nov 15 2007, 06:14 PM
|- - dburt   QUOTE (marsbug @ Nov 15 2007, 11:14 AM) I...   Nov 15 2007, 11:30 PM
|- - Gsnorgathon   Not to rain (metastably or otherwise) on anyone...   Nov 16 2007, 12:41 AM
|- - Juramike   QUOTE (Gsnorgathon @ Nov 15 2007, 08:41 P...   Nov 16 2007, 08:57 PM
|- - nprev   QUOTE (Juramike @ Nov 16 2007, 12:57 PM) ...   Nov 17 2007, 03:49 PM
|- - Juramike   QUOTE (nprev @ Nov 17 2007, 10:49 AM) .....   Nov 17 2007, 05:02 PM
|- - ElkGroveDan   QUOTE (Juramike @ Nov 17 2007, 09:02 AM) ...   Nov 17 2007, 05:38 PM
- - Greg Hullender   Here's a couple of useful comments from a NASA...   Nov 15 2007, 06:41 PM
- - djellison   And of course, the fact that water can exist, at s...   Nov 15 2007, 07:12 PM
|- - rlorenz   QUOTE (djellison @ Nov 15 2007, 02:12 PM)...   Nov 16 2007, 01:47 AM
|- - ngunn   QUOTE (rlorenz @ Nov 16 2007, 01:47 AM) I...   Nov 16 2007, 01:03 PM
- - Juramike   Both theory and experiment agree that cold brine s...   Nov 15 2007, 10:41 PM
- - nprev   Mike or HDP Don, how different are the curves for ...   Nov 16 2007, 01:06 AM
|- - dburt   QUOTE (nprev @ Nov 15 2007, 06:06 PM) Mik...   Nov 16 2007, 08:27 PM
|- - nprev   QUOTE (dburt @ Nov 16 2007, 12:27 PM) Ver...   Nov 17 2007, 01:17 AM
|- - dburt   QUOTE (nprev @ Nov 16 2007, 06:17 PM) Tha...   Nov 17 2007, 01:40 AM
- - ngunn   Thanks for that Hecht link. Definitely some counte...   Nov 16 2007, 08:51 PM
- - nprev   They don't call ya Herr Doktor Professor for n...   Nov 17 2007, 01:50 AM
|- - dburt   QUOTE (nprev @ Nov 16 2007, 06:50 PM) The...   Nov 17 2007, 03:03 AM
- - marsbug   Thank you very much one and all, I can look foward...   Nov 17 2007, 05:25 PM
- - nprev   Rats...knew I shoulda gone to EGD's alma mater...   Nov 18 2007, 12:15 AM
- - Juramike   Space.com article says that the crust of Mars is c...   May 15 2008, 07:03 PM
|- - dburt   QUOTE (Juramike @ May 15 2008, 12:03 PM) ...   May 17 2008, 01:14 AM
||- - dvandorn   QUOTE (dburt @ May 16 2008, 08:14 PM) ......   May 17 2008, 07:06 AM
||- - Juramike   QUOTE (dburt @ May 16 2008, 08:14 PM) Hop...   May 17 2008, 12:53 PM
||- - dburt   QUOTE (Juramike @ May 17 2008, 05:53 AM) ...   May 19 2008, 02:58 AM
||- - SickNick   QUOTE (Juramike @ May 17 2008, 10:53 PM) ...   Jun 8 2008, 02:38 PM
|- - Juramike   QUOTE (Juramike @ May 15 2008, 02:03 PM) ...   May 18 2008, 06:35 PM
- - dvandorn   As a general comment to the "discovery" ...   May 17 2008, 07:17 AM
- - silylene   QUOTE (spdf @ May 24 2007, 12:38 AM) A qu...   May 24 2008, 03:21 AM
|- - rlorenz   QUOTE (silylene @ May 23 2008, 11:21 PM) ...   May 24 2008, 01:27 PM
|- - Juramike   QUOTE (rlorenz @ May 24 2008, 09:27 AM) M...   May 24 2008, 03:05 PM
|- - silylene   I agree that the problem with resonance waves make...   May 25 2008, 02:05 AM
- - Juramike   A rotovap simulation experiment! That...is......   May 24 2008, 04:28 AM


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