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Europa Subsurface Ocean
Guest_Myran_*
post Nov 24 2005, 11:40 AM
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QUOTE
RNeuhaus said: I am still puzzled  of this odd behavior


Did you mean the behavior of the water?

Its not so odd, at 4C water is densest and so tend to sink, so locally where I live we do see upheavels of lake waters when the surface water that have been warmed during the summer get chilled in the autumn and so turn themselves bottom up. This is actually something good, nutrients get brought back and is a reason we have planty of fish in these arctic waters that would have very little life if it wasnt for this fact.
So to adress Richard Trigaux, such convection patterns is the reason that makes me think something might actualy live in that ocean, that said with one emphazis on 'might'. Regardless Europa is our best bet in the solar system for a place where we might find something living.
If there ever will be funding for the extremely exensive project of sending one radiation hardened lander with one automated submarine to prove or disprove the fact is another question. Perhaps only in the very distant future.
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Guest_Richard Trigaux_*
post Nov 24 2005, 02:18 PM
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QUOTE (Myran @ Nov 24 2005, 11:40 AM)
If there ever will be funding for the extremely exensive project of sending one radiation hardened lander with one automated submarine to prove or disprove the fact is another question. Perhaps only in the very distant future.
*



There was already a discution of an Europa "submarine"

But before going so far, a lander could use a charge or chemical fuel to melt some ice, and thus to bury itself into ice and shelter from radiations, with only an antenna out. It this way it could also filter the water for search of bacteria remnants. But for this a landing place must be carefully selected. And anyway the lander will have to remain about one year into Jupiter's radiation belts, the necessary time for the gravitation manoeuvres to reach Europa.
After doing life experiences, this lander would run a seismometre to probe Europa. It could even carry a sonar to probe the ocean.
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Guest_BruceMoomaw_*
post Nov 24 2005, 03:02 PM
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QUOTE (Myran @ Nov 24 2005, 11:40 AM)
Its not so odd, at 4C water is densest and so tend to sink, so locally where I live we do see upheavels of lake waters when the surface water that have been warmed during the summer get chilled in the autumn and so turn themselves bottom up. This is actually something good, nutrients get brought back and is a reason we have planty of fish in these arctic waters that would have very little life if it wasnt for this fact.
*


It has been suggested that this very phenomenon might cause significant fluctuations in the thickness of Europa's ice crust over long periods. That peculiar density property of liquid water means that the remaining geothermal heat coming out of Europa's interior will generate convection currents that actually tend to top off at a short distance below the bottom of the ice layer, at the level where the liquid water's temperature has dropped to 4 deg C. The layer of cooler and less dense liquid water above that will actually serve as a layer of insulation to keep the bottom of the ice layer from being warmed -- since, while liquid water is very effective at spreading heat through CONVECTION, it's lousy at CONDUCTING heat. The result will be a slow buildup of trapped heat in the convective layer, with the top of the churning convective layer rising closer and closer to the bottom of the ice layer as the water underneath gets warmer and warmer -- until the convecting water finally does get warm enough that it rises to touch the bottom of the ice layer, at which point it will cause quite dramatic melting of the lower part of that layer, with the trapped heat in the underlying water ocean escaping at that point. This cyclic phenomenon may be a second factor -- along with the gradual fluctuations in the eccentricity of Europa's orbit caused by the other moons, and thus of its tidal heating -- causing periodic changes in the thickness of the ice crust over periods of tens of millions of years.
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RNeuhaus
post Nov 24 2005, 03:34 PM
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QUOTE (Myran @ Nov 24 2005, 06:40 AM)
Did you mean the behavior of the water?

Its not so odd, at 4C water is densest and so tend to sink, so locally where I live we do see upheavels of lake waters when the surface water that have been warmed during the summer get chilled in the autumn and so turn themselves bottom up. This is actually something good, nutrients get brought back and is a reason we have planty of fish in these arctic waters that would have very little life if it wasnt for this fact.
*

Indeed yes: water wink.gif . I didn't knew about the anomalies of water that is new form me. I don't live in artic zone so I don't see often snow or ice except ones from high Andean mountain when I sometime travel by car. I am not a good knowledge of water as a sand of dunes. biggrin.gif

Rodolfo
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Guest_Richard Trigaux_*
post Nov 24 2005, 04:21 PM
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QUOTE (BruceMoomaw @ Nov 24 2005, 03:02 PM)
It has been suggested that this very phenomenon might cause significant fluctuations in the thickness of Europa's ice crust over long periods.  That peculiar density property of liquid water means that the remaining geothermal heat coming out of Europa's interior will generate convection currents that actually tend to top off at a short distance below the bottom of the ice layer, at the level where the liquid water's temperature has dropped to 4 deg C.  The layer of cooler and less dense liquid water above that will actually serve as a layer of insulation to keep the bottom of the ice layer from being warmed -- since, while liquid water is very effective at spreading heat through CONVECTION, it's lousy at CONDUCTING heat.  The result will be a slow buildup of trapped heat in the convective layer, with the top of the churning convective layer rising closer and closer to the bottom of the ice layer as the water underneath gets warmer and warmer -- until the convecting water finally does get warm enough that it rises to touch the bottom of the ice layer, at which point it will cause quite dramatic melting of the lower part of that layer, with the trapped heat in the underlying water ocean escaping at that point.  This cyclic phenomenon may be a second factor -- along with the gradual fluctuations in the eccentricity of Europa's orbit caused by the other moons, and thus of its tidal heating -- causing periodic changes in the thickness of the ice crust over periods of tens of millions of years.
*


This cyclic behaviour on Europa ocea is interesting. I had some doubt of something like this, but without putting it in image like you.

When you say "hot water" it is relatively hot, say 10-30C, no more (assuming it is pure water). Because hottest than than, it gets much less dense than the water bellow 4C. So this two-layers model is interesting. We may consider too that the upper layer is very pure (it has no movements to mix dust in it) so it can get into a surfusion state (bellow 0C without freezing) and make the mixing still harder, or suddenly freeze at a whole, creating upheavals in the ice layer. I did not knew that water could be so dangerous.
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tty
post Nov 24 2005, 07:42 PM
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QUOTE (Richard Trigaux @ Nov 22 2005, 10:38 PM)
Interesting question.
On Earth, the inner circulation of oceans is dominated by very cold water flowing from the ice shields, and this explains why the bottom of the ocean is very cold (4 and even 2). Occasionally evaporation at the surface can also create currents of more salty (heavier) water, as the one which occurs in the Gibraltar straight. (On Europe there is of course no evaporation, by melting/thawing of ice near the top of the ocean may also produce differences in salinity).
*


That's not quite correct. The cold, salty oceanic bottom water is actually created in the subarctic parts of the Southern Ocean where the surface is cooled by the strong western winds and the surface water then sinks. The meltwater from the arctic ice areas is fresher (and often below +4 Centigrade), hence is lighter and stays at the surface.

tty
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RNeuhaus
post Nov 24 2005, 09:01 PM
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QUOTE (tty @ Nov 24 2005, 02:42 PM)
That's not quite correct. The cold, salty oceanic bottom water is actually created in the subarctic parts of the Southern Ocean where the surface is cooled by the strong western winds and the surface water then sinks. The meltwater from the arctic ice areas is fresher (and often below +4 Centigrade), hence is lighter and stays at the surface.

tty
*

I am enclosing a map of World Ocean Salinity. The most salty water are around in the equatorial zone, Arabia Golf, North and South middle Pacific ocean, in North and South middle Atlantic ocean, and Mediterranean sea. The polar sea has lower salinity (fresher) specialy ones of the North Artic.

http://www.windows.ucar.edu/tour/link=/ear..._gif_image.html

Southern Ocean of Pacific and Atlantic has cold Antartic deep water that flows toward to North hemisphere along western South America coast and I don't know about which side does the flows of cold Antartic water to Atlantic ocean.

Rodolfo
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Decepticon
post Nov 24 2005, 09:40 PM
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When I visit Italy (Calabria) is the province where my parents are from, swimming in the mediterranean is a Salt bath all right.
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tty
post Nov 24 2005, 09:51 PM
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QUOTE (RNeuhaus @ Nov 24 2005, 11:01 PM)
Southern Ocean of Pacific and Atlantic has cold Antartic deep water that flows toward to North hemisphere along western South America coast and I don't know about which side does the flows of cold Antartic water to Atlantic ocean.
Rodolfo
*


The Antarctic Bottom Water (AABW) flows north at depth in all oceans. Here is a sketch that shows how it works.

http://ioc.unesco.org/oceanteacher/resourc...mass/fig7a4.htm

tty
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scalbers
post Nov 24 2005, 10:20 PM
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Thanks Emily for pointing out Bob Pappalardo's Europa class website (back in post #15). In addition to the website name, that would be a pretty cool class to take...


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deglr6328
post Nov 25 2005, 12:01 AM
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Though mainly intended as a refutation of Richard Hoeglands moronic claims to have originated the idea, this page is a wonderful chronicle of the history of the idea of an ocean on Europa. Surprisingly, the idea actually has its roots in the 1950s!!
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Guest_Richard Trigaux_*
post Nov 25 2005, 08:12 AM
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QUOTE (deglr6328 @ Nov 25 2005, 12:01 AM)
Though mainly intended as a refutation of Richard Hoeglands moronic claims to have originated the idea, this page is a wonderful chronicle of the history of the idea of an ocean on Europa. Surprisingly, the idea actually has its roots in the 1950s!!
*


Very interesting paper, very long but well filled.

So in 1971 thre was already people to write that the radioactive decay of uranium in Europe could sustain an ocean, and the later be detectable by its magnetic field!!

Another interesting remark is that 5kms2 of Europa water could be exposed to sunlight every year, due to fracturation of the ice. This makes a fair amount of energy, and certainly a thing to account with when studying the chemistry and eventual ecology of this ocean.
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Guest_BruceMoomaw_*
post Nov 27 2005, 02:32 AM
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The short version of the "cold low-density upper ocean layer" theory about Europa can be found at http://www.lpi.usra.edu/meetings/lpsc2002/pdf/1824.pdf . The longer version, published in the April 2004 "Icarus", is at http://www.lpl.arizona.edu/~rlorenz/europa.pdf .

However, a caution: one thing which I'd forgotten about is that the theorists say that such a phenomenon can NOT occur if either the pressure or the salinity of Europa's ocean rises to levels which, from what we now know, seem very likely for it (an ice layer more than 23 km thick, or a salinity level about equal to that of Earth's ocean). In either case, the density of liquid water simply continues to rise with decreasing temperature until the exact freezing point is reached, and there cannot be a thin surface "stratosphere" of low-density near-freezing liquid water. So it starts to look probable after all that Europa's cycles of thin and thick ice crust probably are entirely due to changes in its level of tidal heating instead.
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ljk4-1
post Jan 26 2006, 06:13 PM
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Two Large Lakes Discovered Under Antarctic Ice

http://www.livescience.com/othernews/06012...ctic_lakes.html

Antarctica has at least 145 small lakes buried under its ice and one large one
called Vostok. Now scientists have found the second and third largest known
bodies of subsurface liquid water there.


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and feel as if I had done some wrong, and it is hard to forget the ugly circumstance.
I see that such intercourse long continued would make one thoroughly prosaic, hard,
and coarse. But the longest intercourse with Nature, though in her rudest moods, does
not thus harden and make coarse. A hard, sensible man whom we liken to a rock is
indeed much harder than a rock. From hard, coarse, insensible men with whom I have
no sympathy, I go to commune with the rocks, whose hearts are comparatively soft."

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Jeff7
post Jan 27 2006, 01:57 AM
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Link was truncated.wink.gif

There we go

I wonder if there are any plans to gather samples from those lakes?
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