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U.Toronto researchers discover clues to early solar system (Forwarded)



 
 
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Old August 6th 07, 10:47 PM posted to sci.astro
Andrew Yee
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Default U.Toronto researchers discover clues to early solar system (Forwarded)

Department of Public Affairs
University of Toronto
Toronto, Ontario

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Department of Public Affairs, 416-978-0100

August 3, 2007

U of T researchers discover clues to early solar system

Crystals on meteorite hold a key to understanding building blocks of
planets

By Karen Kelly

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," said lead author Gopalan Srinivasan, a professor in 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, similar to the process that
happened on 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 nine-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."


 




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