[meteorite-list] New Source Suspected for Ancient Iron Meteorites

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Mar 16 18:08:19 2006
Message-ID: <200603141804.k2EI4MF08609_at_zagami.jpl.nasa.gov>

http://www.space.com/scienceastronomy/060314_science_tuesday.html

New Source Suspected for Ancient Meteorites
By Sara Goudarzi
space.com
14 March 2006

Iron meteorites typically thought to have formed beyond Mars might have
started off closer to the Sun, created from the same material that makes
up the inner planets, new computer models suggest.

Pieces of meteors typically made up of iron, nickel and cobalt, iron
meteorites are leftovers of asteroid-like bodies and are some of the
earliest materials formed in the solar system. These meteorites broke
apart from larger parent bodies and became scattered throughout the
solar system.

After billions of years, some of them find their way to Earth.

The parent bodies of these meteorites probably come from the same disk
of planetary debris that produced the Earth and the other inner planets,
explained William Bottke of the Southwest Research Institute.

"This means that certain iron meteorites may tell us what the precursor
material for the primordial Earth was like," said Bottke. "There's also
the possibility that larger versions of this material may still be
hiding among the asteroids. The hunt for them is on."

The problem in trying to use these objects for understanding Earth,
however, has been that most meteorites come from the distant asteroid
belt, a region of the solar system between the Mars and Jupiter.
Meteorites from that location tend to give clues about how things formed
in that region and not around Earth.

However, simulations suggest that this may not be the case.

Although these iron meteorites reside in the distant asteroid belt,
Bottke and his team found through computer simulations that the parent
bodies were most likely formed in the inner solar system closer to Earth.

They verified this by looking at the composition of iron meteorites,
which originated from cores of melted asteroids from early on in solar
system history. This matched up with the computer model results of the
kind of bodies that formed near Earth.

They also used their computer models to see how and where these objects
have traveled through time. Simulations showed that some asteroid-like
bodies spread out far enough to end up in the asteroid belt.

"While the amount of material reaching the asteroid belt was limited,
much of it was placed in regions likely to produce meteorites," said
SwRI researcher David Nesvorny. "En route to the asteroid belt, the
parent bodies of the iron meteorites were repeatedly bashed by other
bodies, allowing core fragments from numerous bodies to escape."

The study was detailed in the February 17 issue of Nature.
Received on Tue 14 Mar 2006 01:04:22 PM PST