Re: Europa and energy transfer

On Wed, 30 Oct 2024 22:05:55 +0000, x wrote:

On 10/29/24 21:53, Sylvia Else wrote:

NASA has a mission to the Jovian system, to study Europa. That moon is
interesting because it appears to have liquid water under an icy
surface. The heat need to keep the water liquid comes from the
stretching and compression Europa experiences during its orbit around
Jupiter, the orbit not been exactly circular.
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So much, so simple.
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Some thought made me realise that although the tidal forces on Europa
mean that it is not exactly spherical, its two bulges cannot remain
perfectly aligned with Jupiter, because Europa's angular velocity
relative to Jupiter is higher at periapsis than at apoapsis. The result
is that the nearer bulge is sometimes ahead, and sometimes behind,
relative to Europa's orbital motion, resulting in a net force backwards
along the orbit, or forward along the orbit.
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Again, certainly stuff that's already well known.
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As far as I can see, the energy that is being dissipated as heat inside
Europa has to come from changes to Europa's orbit. Further, if Europa
were either perfectly rigid, or perfectly elastic, there would be no
energy transfer, and consequently no change to the orbit.
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It would make no difference if Jupiter itself were perfectly rigid, so
the transfer cannot involve tides on Jupiter generated by Europa.
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So the existence of the orbital energy transfer depends on Europa being
neither perfectly rigid nor perfectly elastic.
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What escapes me is the mechanism.
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Any thoughts?

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I am thinking that the standard model for Earth is that supposedly
in the 1800s Lord Kelvin did some calculations.

At that time they had thought the universe was only full of stars. They
had no clue about galaxies and intergalactic distances and so they
considered the universe finite as it would be bright if finite.
Throw out Kelvin and Helmholtz and Einstein and Feynman.
Up Galileo and Newton and Maxwell and Tesla.

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The outer layers of the Earth have an insulating effect on the inner
layers of the earth.
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Then the inner layers even can act as more insulation.
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And further down.
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And so on.
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He calculated that it would take a hot interior literally 10s to
even 100 million years for a hot Earth interior to cool down because
the Earth could retain heat and insulate successive layers so well.
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When everything was put together, however, his calculations were not
wrong.
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The standard model of geologic time in the present however is that the
Earth is billions of years old.
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How is this discrepancy resolved?
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I am thinking that the standard modern view is that radiation from
the slow radioactive decay of uranium, potassium, thorium, and other
elements deep in the interior is added to the Earth's insulating
effect to keep the interior of the Earth and other inner solar system
bodies heated.
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I am thinking that Io is supposed to be rather seriously affected
in its composition and internal dynamics by tidal forces.  I was
thinking however that Ganymede and Callisto were also supposed to
have liquid water mantles.
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It might be that there is a combination of insulation, internal
radiation, and tidal forces going on for the different moons
of Jupiter.