Europa Subsurface Ocean |
Europa Subsurface Ocean |
Nov 22 2005, 10:53 AM
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#1
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
Regarding the very real possibility Europa harbors an ocean underneath the ice, I'm wondering whether there have been any estimates on how long such an ocean might have been sustained (I'm assuming it's still there today). Are we talking about the entire history of Europa, billions of years or a much more recent thing, only a few millions? I know Enceladus, which recently turned out to be much warmer inside than expected, could have been periodically heated, but not on very long timescales.
I'm primarily interested because of the habitability factor, obviously an ocean which freezes out every once and a while would not make for a good incubator to possible life. Also, supposedly all tidal heating on Europa would cease now, how long would it take for the subsurface to freeze out, that is, what are the thermal conductive properties of the surface ice? Admittedly, I haven't done much research on the subject and if the question was already asked before, I apologize. -------------------- |
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Nov 22 2005, 02:47 PM
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#2
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Member Group: Members Posts: 903 Joined: 30-January 05 Member No.: 162 |
I don't imagine I'm an expert on this, but wouldn't Europa freeze from the top down, and warm (from tidal effects) from the bottom up?
This would keep the 'interesting' part of Europa, the bottom of the water layer, the last to freeze and the first to thaw. If the heating and cooling periods (if there is variation) aren't too intermittent, we shouldn't freeze the 'potential life zone'. IIRC, microbes have been found deep under the sea floor on earth, so perhaps potential Europan life forms have a much larger volume of Europa to live in than we think. |
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Nov 22 2005, 03:35 PM
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#3
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Senior Member Group: Members Posts: 3648 Joined: 1-October 05 From: Croatia Member No.: 523 |
QUOTE (tasp @ Nov 22 2005, 04:47 PM) I don't imagine I'm an expert on this, but wouldn't Europa freeze from the top down, and warm (from tidal effects) from the bottom up? This would keep the 'interesting' part of Europa, the bottom of the water layer, the last to freeze and the first to thaw. That's precisely the reason I asked about the thermal properties of the upper ice layer - that's the only way for heat from the interior to escape into space, if the ice is very non-conductive, it could serve as a blanket preserving the warm water beneath. QUOTE If the heating and cooling periods (if there is variation) aren't too intermittent, we shouldn't freeze the 'potential life zone'. If you don't freeze out, but you do cut out any heating, the organisms wouldn't have any thermal hotspots/vents on the ocean bottom to acquire energy/food from. So, simply keeping the ocean in a liquid state probably doesn't help all that much, but I'm really no expert on biology. -------------------- |
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Guest_Richard Trigaux_* |
Nov 22 2005, 05:43 PM
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#4
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Guests |
Europa ice crust is not much thicker than the Antarctic ice shield. The later is already insulating enough to keep a thin layer of layer molten by geothermal heating. So at a very rough guess, the Europa ocean would freeze in at least thousands of years, at last some million of years. This allows it to be sensitive to periods where there would be no tidal heating, the later having a time scale of hundreds of million to billion years. So yes it would freeze, but no we do not know if it had periods without tidal heating. My personal opinion would be that the whole set of Jovian moons evolve slowly all together. If there had be a special event, a moon taking a special orbit, the strong resulting tidal heating would have quickly corrected this. So I rather think that the overal shift in orbits of the whole four moons is correlated, slow, quasistatic*, resulting into a relatively constant tidal heating. An oposite argument is that Ganymede shows clear surface fractures indicating a more localisated tidal heating event, ancient but not at the beginning. Perhaps the moons were set otherwise at the beginning, and when they reached their today orbits, there was a surge of heating. Of heating, not of freezing. We can wonder if Europe began to have liquid water at this epoch (3billion years ago at rough guess, after ganymede craters). This still makes a long continuous period of time.
*quasistatic: a movement slow enough so that at a given moment we can reason as if nothing was moving. |
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