[meteorite-list] Livermore Lab Chemist Accurately Dates First Objects To Form In The Solar System

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:08:22 2004
Message-ID: <200209062024.NAA19417_at_zagami.jpl.nasa.gov>

Lawrence Livermore National Laboratory
U.S. Department of Energy
Livermore, California

Contact: Anne M. Stark
Phone: (925) 422-9799
E-mail:stark8_at_llnl.gov

FOR IMMEDIATE RELEASE: September 5, 2002

Livermore lab chemist accurately dates first objects to form in
the solar system

LIVERMORE, Calif. -- A geochemist from the Lawrence Livermore
National Laboratory, teaming with researchers from the Royal
Ontario Museum, the University of Hawaii and Moscow State
University, has accurately dated Calcium Aluminum-rich
inclusions (CAIs), the oldest objects in our solar system, to
be 4.57 billion years old.

In addition, the team has determined that chondrules, another
of the earliest objects in the solar system, are 2 to 3
million years younger than CAIs.

The findings, by Ian Hutcheon of LLNL, Yuri Amelin of the
Royal Ontario Museum, Alexander Krot of the University of
Hawaii and Alexander Ulyanov of Moscow State University, will
be published in the Sept. 6, 2002 edition of Science. The
article is titled "Pb Isotopic Ages of Chondrules and Ca-Al
Rich Inclusions."

Using mass spectrometers to study CAIs and chondrules found
in chondritic meteorites, the team was able to determine the
ages of the objects by measuring the decay of uranium 238,
which is found in both objects and decays into lead. Using
an ion microprobe, Hutcheon dated CAIs and chondrules by
detecting the decay of aluminum 26 -- also found in both
objects -- into magnesium 26.

By comparing the lead and magnesium isotope contents in the
CAIs and chondrules, the team determined how old the objects
are. Aluminum 26 decays much faster than uranium, and these
measurements enabled the team to determine the small difference
in age between CAIs and chondrules with unprecedented precision.

"This is the first piece of evidence proving that CAIs are 2
to 3 million years older than chondrules," Hutcheon said. "We
were able to make this conclusion based on our measurements."
CAIs and chondrules are millimeter-size objects found in
primitive meteorites. They formed when dusty regions of the
solar nebula were heated to very high temperatures. The dust
melted and then crystallized, forming first CAIs and then
chondrules. Larger objects, like asteroids and planets, took
longer to form and are about 10 to 50 million years younger
than the CAIs and chondrules.

"All these objects didn't just form in a snap," Hutcheon said.
"By determining the ages of CAIs and chondrules, we can better
date asteroids and planets and learn more about the early
history of the solar system."

Founded in 1952, Lawrence Livermore National Laboratory is
a national security laboratory, with a mission to ensure
national security and apply science and technology to the
important issues of our time. Lawrence Livermore National
Laboratory is managed by the University of California for
the U.S. Department of Energy's National Nuclear Security
Administration.
Received on Fri 06 Sep 2002 04:24:17 PM PDT