[meteorite-list] Lunar capture theory

From: Matson, Robert <ROBERT.D.MATSON_at_meteoritecentral.com>
Date: Thu Apr 22 10:21:02 2004
Message-ID: <AF564D2B9D91D411B9FE00508BF1C86901B4EB6E_at_US-Torrance.mail.saic.com>

Tom wrote:

> I do not believe the moon was made by a asteroid impact on the
> earth.

What, specifically, about this theory bothers you?

> I would first stand by the theory that it was caught up in our
> gravity.

While this is a ~possible~ scenario, you have to understand how
extremely unlikely graceful capture is compared to impact.
The capture idea also has a difficult time explaining why the
Moon doesn't have a normal-sized core for a body of its size,
which the impact theory explains nicely. Finally, why the
oxygen-isotope similarity of earth and the Moon if the two
bodies formed in different parts of the solar system?

Prior to the Apollo sample return missions (and the discovery
of our beloved lunar meteorites), the capture theory at least
had some wobbly legs to stand on. But O-isotope analysis of
the moon rocks knocked one leg out, and the other leg was swept
away by Lunar Prospector's confirmation that the moon's core
comprises less than 3% of the moon's mass.

--Rob
Received on Fri 11 Jul 2003 04:01:33 PM PDT