[meteorite-list] Crystals on Meteorite Reveal Clues to Early SolarSystem Evolution

[Jerry]

For anyone interested in viewing the parent body referred to in this 
article, Aug 29 and 30 provide a splendid backdrop with the bright Jupiter 
at center stage.Larry Lebofsky[many of you know that Larry's first "Love" 
was astroids before being stung by the "ite virus"] sent me a picture from 
S&T depicting this relatively easy viewing[given two consecutive clear skied 
night, iffy for New England] which I forwarded to the list. If anyone missed 
it, I'd be more than happy to provide that picture again.
Jerry Flaherty
----- Original Message ----- 
From: "Darren Garrison" <cynapse at charter.net>
To: <Meteorite-list at meteoritecentral.com>
Sent: Wednesday, August 01, 2007 11:08 PM
Subject: [meteorite-list] Crystals on Meteorite Reveal Clues to Early 
SolarSystem Evolution


http://www.newswise.com/articles/view/532104/

Newswise - A University of Toronto-led study has uncovered tiny zircon 
crystals
in a meteorite originating from Vesta (a large asteroid between Mars and
Jupiter) shedding light on the formation of planetesimals, small 
astronomical
objects that form the basis of planets.

To date, studying zircons in eucrites - meteorites formed by volcanic 
activity -
has been difficult due to impact- induced fracturing and their small size,
typically less than five microns. Most eucrites are formed within the 
asteroid
belt that orbits Mars and Jupiter, a heap of astronomical debris from the
earliest epoch of the solar system. In a study published in the recent issue 
of
Science, researchers collected samples from eucrites found in Antarctica
believed to have originated from Vesta. The researchers used new technology 
to
reveal that asteroid's boiling rock turned solid and crystallized within 
less
than 10 million years of solar system formation.

"Until now we have not been able to determine this time frame 
unambiguously,"
says lead author Professor Gopalan Srinivasan of U of T's Department of 
Geology.
"By pinpointing the timeframe we're able to add one more piece to the 
geological
and historical map of our solar system."

Scientists believe that at some point Vesta was quickly heated and then 
melted
into a metallic and silicate core, a similar process that happened on the 
Earth.
The energy for this process was released from the radioactive decay that was
present in abundance in the early solar system. What has been unclear is 
when
this process occurred. Equipped with the ion microprobe at the Swedish 
National
Museum, Srinivasan and colleagues from four institutions set to analyze the
zircons in the eucrites, which formed when a radioactive element - 
hafnium-182 -
was still alive. Radioactive hafnium-182 decays to another element -
tungsten-182 - with a nearly 9 million year half-life span. By studying 
zircons
for their 182 tungsten abundance, the researchers were able to determine the
crystallization ages of eucrites occurred within that timeframe.

"Zircons on Earth and in space have basically the same characteristics,"
Srinivasan says. "They occur when boiling rock crystallizes and turns into 
solid
form primary crystallization products or they could be secondary products 
caused
by heating from impacts. We know Vesta became inactive within first 10 
million
years of solar system formation which is nearly 4.5 billion years ago. This
provides a snapshot of the early solar system and clues to the early 
evolution
of Earth's mantle and core."
______________________________________________
Meteorite-list mailing list
Meteorite-list at meteoritecentral.com
http://six.pairlist.net/mailman/listinfo/meteorite-list