Meteorites Discovered to Carry Interstellar Carbon

http://www.carnegieinstitution.org/m...s/default.html

Carnegie Institution News Release
Thursday May 4, 2006

Carnegie contacts:
Henner Busemann, 202- 478-8463, cell 202-413-7834,


Conel Alexander, 202-478-8478,

Larry Nittler, 202-478-8460, cell 202-904-9522,

Meteorites discovered to carry interstellar carbon

WASHINGTON, DC - Like an interplanetary spaceship carrying passengers,
meteorites have long been suspected of ferrying relatively young
ingredients of life to our planet. Using new techniques, scientists at
the Carnegie Institution's Department of Terrestrial Magnetism have
discovered that meteorites can carry other, much older passengers as
well - primitive, organic particles that originated billions of years
ago
either in interstellar space, or in the outer reaches of the solar
system as it was beginning to coalesce from gas and dust. The study
shows that the parent bodies of meteorites - the large objects from the
asteroid belt - contain primitive organic matter similar to that found
in
interplanetary dust particles that might come from comets. The finding
provides clues about how organic matter was distributed and processed
in
the solar system during this long-gone era. The work is published in
the
May 5, 2006, issue of Science.

"Atoms of different elements come in different forms, or isotopes, and
the relative proportions of these depend on the environmental
conditions
in which their carriers formed, such as the heat encountered, chemical
reactions with other elements, and so forth," explained lead author
Henner Busemann. "In this study we looked at the relative amounts of
different isotopes of hydrogen (H) and nitrogen (N) associated with
tiny
particles of insoluble organic matter to determine the processes that
produced the most pristine type of meteorites known. The insoluble
material is very hard to break down chemically and survives even very
harsh acid treatments."

The researchers used a microscopic imaging technique to analyze the
isotopic composition of insoluble organic matter from six carbonaceous
chondrite meteorites - the oldest type known. The relative proportion
of
isotopes of nitrogen and hydrogen associated with the insoluble organic
matter act as "fingerprints" and can reveal how and when the carbon was
formed. The isotope of nitrogen that is most often found in nature is
14N; its heavier sibling is 15N. Differing amounts of 15N, in addition
to a heavier form of hydrogen called deuterium, (D), allow researchers
to tell if a particle is relatively unaltered from the time when the
solar system was first forming.

"The tell-tale signs are lots of deuterium and 15N chemically bonded to
carbon," commented co-author Larry Nittler. "We have known for some
time, for instance, that interplanetary dust particles (IDP), collected
from high-flying airplanes in the upper atmosphere, contain huge
excesses of these isotopes, probably indicating vestiges of organic
material that formed in the interstellar medium. The IDPs have other
characteristics indicating that they originated on bodies - perhaps
comets - that have undergone less severe processing than the asteroids
from which meteorites originate."

The scientists found that some meteorite samples, when examined at the
same tiny scales as interplanetary dust particles, actually have
similar
or even higher abundances of 15N and D than those reported for IDPs.
"It's amazing that pristine organic molecules associated with these
isotopes were able to survive the harsh and tumultuous conditions
present in the inner solar system when the meteorites that contain them
came together," reflected co-author Conel Alexander. "It means that the
parent bodies - the comets and asteroids _ of these seemingly different
types of extraterrestrial material are more similar in origin than
previously believed."

"Before, we could only explore minute samples from IDPs. Our discovery
now allows us to extract large amounts of this material from
meteorites,
which are large and contain several percent of carbon, instead of from
IDPs, which are on the order of a million million times less massive.
This advancement has opened up an entirely new window on studying this
elusive period of time," concluded Busemann.

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This work is supported by NASA, through the NASA Astrobiology Institute
(NAI) and the Cosmochemistry Research Program, and the Carnegie
Institution.

The Carnegie Institution of Washington has been a pioneering force in
basic scientific research since 1902. It is a private, nonprofit
organization with six research departments throughout the U.S. Carnegie
scientists are leaders in plant biology, developmental biology,
astronomy, materials science, global ecology, and Earth and planetary
science. See www.carnegieinstitution.org .

The NAI, founded in 1998, is a partnership between NASA, 16 major U.S.
teams and six international consortia. NAI's goal is to promote,
conduct, and lead integrated multidisciplinary astrobiology research
and
to train a new generation of astrobiology researchers. For more
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