Astrophysicists Observe Anomalies in Makeup of Interplanetary Dust Particle

http://www.llnl.gov/llnl/06news/News...-04-02-15.html

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Lawrence Livermore National Laboratory
FOR IMMEDIATE RELEASE
February 26, 2004

Astrophysicists Observe Anomalies in Makeup of Interplanetary Dust Particle

LIVERMORE, Calif. -- Scientists from Lawrence Livermore National Laboratory
and Washington University have seen carbon and nitrogen anomalies on a
particle of interplanetary dust that provides a clue as to how interstellar
organic matter was incorporated into the solar system.

Interplanetary dust particles (IDPs) gathered from the Earth's stratosphere
are complex collections of primitive solar system material and carry various
isotopic anomalies. Using an ion microprobe that allows isotopic imaging at
a scale of 100 nanometers, the astrophysicists conducted simultaneous carbon
and nitrogen isotopic imaging measurements of the IDP, nicknamed Benavente.
They noticed that the isotope carbon 13 decreased while nitrogen 15
increased in Benavente.

The results appear in the Feb. 27 issue of the journal Science.

Interstellar molecular clouds are the principal formation sites of organic
matter in the Milky Way. A variety of simple molecules are produced in dense
cold clouds. At such low temperatures, where the difference in chemical
binding energy exceeds thermal energy, mass fractionation produces molecules
with isotopic ratios that can be very different from molecules found on
Earth.

These anomalies may provide a fingerprint for how abiotic interstellar
organic matter was incorporated into the solar system.

The authors concluded that the observation of correlated carbon and nitrogen
anomalies establishes that IDPs contain heteroatomic organic compounds of
presolar interstellar origins that are more complex than the simple
compounds implied by earlier measurements. During the prebiotic period,
Earth may have accreted as much as a centimeter of abiotic carbonaceous
matter every million years, much of it settling to the surface within small,
high-surface-area IDPs. "This constant flux of particulate organic matter
continues to be delivered to the surface of terrestrial planets today and
includes hetero-atomic interstellar molecules such as those found in
Benavente. It is not unreasonable to speculate that heteroatomic
interstellar molecular matter may be relevant to the origins of life on
earth" said John Bradley, director of Livermore's Institute for Geophysics
and Planetary Physics and one of the authors of the paper. Other Livermore
authors include Zurong Dai, Sasa Bajt and Giles Graham.

Images of an IDP can be found at
http://www.llnl.gov/llnl/06news/NewsMedia/stardust.html

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