Re: Europa and energy transfer

On Sat, 2 Nov 2024 5:14:11 +0000, Physfitfreak wrote:

On 11/1/24 23:52, Sylvia Else wrote:

On 30-Oct-24 12:53 pm, 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?

>
Perhaps I was naive to think anyone would address the essence of my
post, rather than going off at massive tangent.
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Sylvia.

>
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Yes. You were naive to think sci.physics is a classroom.

Now that's fummy, Roachie.
Only real teacher of physics is Arindam.
Woof-woof
Bertietaylor.