[meteorite-list] "Young" chondrules discovered in Gujba and an HAH

[Pete Pete]

Those trouble-making Canadians...always rockin' the boat! ;]

This will be an interesting one to watch for development!

Cheers,
Pete

From: Darren Garrison <cynapse at charter.net>
Reply-To: cynapse at charter.net
To: Meteorite Mailing List <meteorite-list at meteoritecentral.com>
Subject: [meteorite-list] "Young" chondrules discovered in Gujba and an HAH
Date: Thu, 18 Aug 2005 18:57:21 -0400

http://www.news.utoronto.ca/bin6/050818-1567.asp

Discovery of 'young' material in meterorites defies linear theory of solar 
system's origin
>From order to disorder: A monkey wrench in solar system evolution?
Aug 18/05
by Sonnet L’Abbé
A U of T scientist has found unexpectedly ‘young’ material in meteorites 
– a discovery that breaks
open current theory on the earliest events of the solar system.

A paper published today in the August issue of Nature reports that the 
youngest known chondrules –
the small grains of mineral that make up certain meteorites – have been 
identified in the meteorites
known as Gujba and Hammadah al Hamra.

Researchers who have studied chondrules generally agree that most were 
formed as a sudden,
repetitive heat, likely from a shock wave, condensed the nebula of dust 
floating around the early
Sun. Thinking that an analysis of the chondrules in Gujba and Hammadah al 
Hamra would be appropriate
for accurately dating this process, U of T geologist Yuri Amelin, together 
with lead author
Alexander Krot of the University of Hawaii, studied the chondrules’ 
mineralogical structure and
determined their isotopic age. “It soon became clear that these particular 
chondrules were not of a
nebular origin,” says Amelin. “And the ages were quite different from 
what was expected. It was
exciting.”

Amelin explains that not only were these chondrules not formed by a shock 
wave, but rather emerged
much later than other chondrules. “They actually post-date the oldest 
asteroids,” he says. “We think
these chondrules were formed by a giant plume of vapour produced when two 
planetary embryos,
somewhere between moon-size and Mars-size, collided.”

What does this mean in the grand scheme of things? The evolution of the 
solar system has
traditionally been seen as a linear process, through which gases around the 
early sun gradually
cooled to form small particles that eventually clumped into asteroids and 
planets. Now there is
evidence of chondrules forming at two very distinct times, and evidence that 
embryo planets already
existed when chondrules were still forming. “It moves our understanding 
from order to disorder,”
Amelin admits. “But I’m sure that as new data is collected, a new order 
will emerge.”

Financial support for this project was provided by NASA and the Canadian 
Space Agency
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