Europa Subsurface Ocean |
Europa Subsurface Ocean |
Nov 22 2005, 10:53 AM
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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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Guest_BruceMoomaw_* |
Nov 22 2005, 10:43 PM
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#2
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Guests |
Virtually all the papers on the subject have concluded that -- while the thickness of the ice crust may very well oscillate up and down, over periods of seveal tens of millions of years, between just a few kilometers and up to 50 km or so -- Europa's ocean has never frozen out completely since the moon was formed.
Indeed, this factor was the main reason why scientists before Galileo's data were so hesitant to make a firm prediction as to whether or not an ocean existed at all: if a liquid ocean existed at the start, it would likely sustain its own existence, because the friction from the tidal bulging and flexing of the ocean and the ice shell above it would generate enough heat to keep the ocean liquid -- but if Europa's surface water layer had been frozen full through and thus rigid from the start, its tidal flexing would be so small that it wouldn't generate enough heat to melt itself. Well, now we know from Galileo's induced magnetic field data that -- barring one of the biggest shocks in the history of science -- Europa DOES have a substantial subsurface ocean, and thus always has had one. (I've never seen any paper suggesting that the fluctuations in its degree of tidal heating resulting from the slow orbital shifts of the Galilean moons might, at ANY time in its past history, have generated enough additional heat to melt a fully frozen ice layer on it. I suppose this can't quite be ruled out yet -- after all, calculations indicate that Ganymede got jockeyed into a quite eccentric orbit about a billion years ago which generated enough heat to create its current still-molten central core -- but, as I say, I've never read any such suggestion about Europa.) |
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