(meteorobs) Fw: Carnegie: Meteorite Holds Clues to Organic Chemistry of Early Earth

[Thilina Heenatigala]

Below release may interest some of you.

Cheers!
Thilina



METEORITE HOLDS CLUES TO ORGANIC CHEMISTRY OF THE EARLY EARTH

Carbonaceous chondrites are a type of organic-rich meteorite that
contain samples of the materials that took part in the creation of our
planets nearly 4.6 billion years ago, including materials that were
likely formed before our solar system was created and may have been
crucial to the formation of life on Earth. The complex suite of
organic materials found in carbonaceous chondrites can vary
substantially from meteorite to meteorite. New research from
Carnegie's Department of Terrestrial Magnetism and Geophysical
Laboratory, published June 10 in Science, shows that most of these
variations are the result of hydrothermal activity that took place
within a few million years of the formation of the solar system, when
the meteorites were still part of larger parent bodies, likely
asteroids.

Organic material in carbonaceous chondrites shares many
characteristics with organic matter found in other primitive samples,
including interplanetary dust particles, comet 81P/Wild-2, and
Antarctic micrometeorites. It has been argued by some that this
similarity indicates that organic material throughout the solar system
largely originated from a common source, possibly the interstellar
medium.

A test of this common-source hypothesis stems from its requirement
that the organic diversity within and among meteorites be due
primarily to chemical and thermal processing that took place while the
meteorites were parts of their parent bodies. In other words, there
should be a relationship between the extent of hydrothermal alteration
that a meteorite experienced and the chemistry of the organic material
it contains.

If -- as many have speculated -- the organic material in meteorites
had a role to play in the origin of life on Earth, the attraction of
the common-source hypothesis is that the same organic material would
have been delivered to all bodies in the solar system. If the common
source was the interstellar medium, then similar material would also
be delivered to any forming planetary system.

The research team -- led by Christopher Herd of the University of
Alberta, Canada, and including Carnegie's Conel Alexander, Larry
Nittler, Frank Gyngard, George Cody, Marilyn Fogel, and Yoko Kebukawa
-- studied four meteorite specimens from the shower of stones,
produced by the breakup of a meteoroid as it entered the atmosphere,
that fell on Tagish Lake in northern Canada in January 2000. The
samples are considered very pristine, because they fell on a frozen
lake, were collected without hand contact within a few days of
landing, and have remained frozen ever since.

The samples were processed and analyzed on the microscopic level using
a variety of sophisticated techniques. Examination of their inorganic
components indicated that the specimens had experienced large
differences in the extent of hydrothermal alteration, prompting an
in-depth examination of their organic material. The team demonstrated
that the insoluble organic matter found in the samples has properties
that span nearly the entire range found in all carbonaceous chondrites
and that those properties correlate with other measures of the extent
of parent body alteration. Their finding confirms that the diversity
of this material is due to processing of a common precursor material
in the asteroidal parent bodies.

The team found large concentrations of monocarboxylic acids, or MCAs,
which are essential to biochemistry, in their Tagish Lake samples.
They attributed the high level of these acids to the pristine nature
of the samples, which have been preserved below zero degrees Celsius
since they were recovered. There was variety in the types of MCAs,
which they determined could also be due to alterations that took place
on the parent bodies.

The samples also contained amino acids -- the essential-for-life
organic building blocks used to create proteins. The types and
abundances of amino acids contained in the samples are consistent with
an extraterrestrial origin, and were clearly also influenced, albeit
in a complex way, by the alteration histories of their host
meteorites.

"Taken together these results indicate that the chemical and thermal
processing common to the Tagish Lake meteorites likely occurred when
the samples were part of a larger parent body that was created from
the same raw materials that formed our solar system," said Larry
Nittler of Carnegie's DTM. "These samples can also provide important
clues to the source of organic material, and life, on Earth."



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Thilina Heenatigala.
Project Coordinator
Astronomers Without Borders (AWB)

email: thilina at astronomerswithoutborders.org             phone:     +94 716 245 545
web:   http://www.astronomerswithoutborders.org/    twitter:    @ThilinaH
blog:   http://thilinaheenatigala.blogspot.com             facebook: thilina.heenatigala
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