[meteorite-list] Did The New Moon Lose Its Iron Heart?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue, 23 Jan 2007 13:17:25 -0800 (PST)
Message-ID: <200701232117.NAA14864_at_zagami.jpl.nasa.gov>

http://space.newscientist.com/article/mg19325875.700-did-the-new-moon-lose-its-iron-heart.html

Did the new moon lose its iron heart?
New Scientist
23 January 2007

The moon may not be just a chip off the old planetary block. It could
have formed at the same time as Earth from the same primordial stuff.

The current theory says that the material that now forms our moon was
ejected when Earth was struck by another planet-sized body. But Peter
Noerdlinger at Saint Mary's University in Halifax, Canada, says this
theory has problems. "The collision has to be implausibly gentle. You
practically need someone to hold a Mars-sized object just above Earth
and drop it, to avoid messing up Earth's orbit."

The simpler idea that Earth and the moon were both created from the
same gas cloud had been rejected because it could not explain why
Earth formed an iron core and the moon did not. Now, Noerdlinger has
an answer for that.

He suggests that the proto-moon did have an iron core, but that the
satellite was ripped apart in a close encounter with Earth. His
calculations show that iron from the core would be pulled towards
Earth, while the remains of its rocky outer shell reassembled into
our iron-free moon.

This fits with evidence that the Earth acquired a veneer of iron
after it formed, Noerdlinger says. He presented the work at the
American Astronomical Society meeting in Seattle, Washington, last
week.

>From issue 2587 of New Scientist magazine, 23 January 2007, page 16
Received on Tue 23 Jan 2007 04:17:25 PM PST