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Well, it's not *my* out and back again model.
I don't see how slowing the system down further would cause the moon to come back in and speed up. Wait a minute.... the earth's tidal bulges lead the moon, increasing its angular momentum and causing it to move out and slow down. If the earth's bulges were to lag the moon, it would want to *decrease* the moon's angular momentum, causing it to move in and speed up. This would cause the earth to speed up again, because the time scale for earth-moon locking is so much shorter for earth-sun locking.
Okay. I'm convinced. [img]/phpBB/images/smiles/icon_smile.gif[/img]
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That's general situation when a moon orbits the planet faster than the planet rotates. Phobos does that, except it is inside Mars' Roche limit already, so the fact Phobos is holding together implies it is a solid rock rather than a rubble pile. In any case, I read that Phobos will crash into Mars in 40 million years.
BTW, if a moon orbits the planet
against the planet's rotation, the tides also bring the moon closer. In 100 million years Triton will reach Neptune's Roche limit and will become a spectacular ring...