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View Diary: Getting to Know Your Solar System (28): Saturn (Vol. 3) (42 comments)

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  •  2 things: Why doesn't Enceladus just disappear (1+ / 0-)
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    eventually if 300 to 600 kg are being blasted off its surface every second?

    And why is it that of the terrestial planets, only Earth has a molten outer core capable of generating a magnetic field?

    You have exactly 10 seconds to change that look of disgusting pity into one of enormous respect!

    by Cartoon Peril on Thu Apr 18, 2013 at 03:36:45 PM PDT

    •  Consider the total mass of Enceladus. (2+ / 0-)
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      Cartoon Peril, Khun David

      It's on order of 1020 kilograms - hundreds of quintillions.  At a rate of 1000 kg per second, it would take 31 billion years to disappear completely - just this side of three times the age of the universe.

      As to Earth's core, Mercury has a molten outer core too, which is why it too has a magnetic field.  Earth has such a strong one partly because the giant impactor that formed the moon donated a lot of iron and caused Earth to spin faster (the day was only 4 hours immediately after impact, and has been slowing since).  So while the Earth still rotates significantly, the molten core will convect and generated a dynamo.

      Venus doesn't have a field because it barely rotates at all, so whatever convection occurs in the molten core isn't very efficient.  And Mars doesn't have a field because it's small and was able to cool more quickly, so it's internally "mostly dead."

      Democracy is a habit, not a circumstance.

      by Troubadour on Thu Apr 18, 2013 at 03:58:28 PM PDT

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    •  Correction: Order of 10^19. (1+ / 0-)
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      Cartoon Peril

      So it would only be 3.1 billion years, meaning that Enceladus originally formed with considerably more mass than it has today, or else was less active in the past.

      Democracy is a habit, not a circumstance.

      by Troubadour on Thu Apr 18, 2013 at 04:18:16 PM PDT

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