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Re: Moonquakes

Subject: Re: Moonquakes
From: Henry Spencer
Date: Fri, 17 Mar 2006 02:21:29 GMT
Newsgroups: sci.astro, alt.sci.planetary, sci.geo.earthquakes
In article <[email protected]>,
rick++ <[email protected]> wrote:
>There three competing theories: simultaneous acretion,
>capture, and proto-earth fission after collision.

The original three theories -- spin fission, simultaneous accretion, and
capture (sometimes described as "daughter", "sister", and "wife") -- all
died when the Apollo samples were analyzed.  Lunar rocks are too similar
to Earth's to have had an independent origin, and too different to have
had the same history. 

The giant-impact theory -- there's no real "fission" involved, as there
was one body only for a brief moment during the impact -- emerged from
several directions at once as the only convincing explanation.  Earth and
Moon have more or less a common origin, but the Moon formed from impact
debris splashed up by an off-center impact, and thus -- among other
differences -- its material got much hotter than Earth did, explaining
the differences.
-- is temporarily off the air;               |   Henry Spencer
mail to henry at instead.               | [email protected]

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