by Playfuls Staff |
1st December 2006
NASA researchers at
Johnson Space
Center,
Houston have found organic materials that
formed in the most distant reaches of the early Solar System preserved in a
unique meteorite. The study was performed [more] on the
Tagish Lake
carbonaceous chondrite, a rare type of meteorite that is rich in organic
(carbon-bearing) compounds.
Organic matter in meteorites is a
subject of intense interest because this material formed at the dawn of the
Solar System and may have seeded the early Earth with the building blocks of life.
The Tagish Lake
meteorite is especially valuable for this work because much of it was collected
immediately after its fall over Canada
in 2000 and has been maintained in a frozen state, minimizing terrestrial
contamination. The collection and curation of the meteorite samples preserved
its pristine state.
In a paper published in the Dec.
1 issue of the journal Science, the team, headed by NASA space scientist Keiko
Nakamura-Messenger, reports that the Tagish
Lake meteorite contains
numerous submicrometer hollow organic globules.
"Similar objects have been
reported from several meteorites since the 60"s. Some scientists believed
these were space organisms, but others thought they were just terrestrial
contamination," said Nakamura-Messenger. The same bubble-like organic
globules appeared in this freshest meteorite ever received from space.
"But in the past, there was no way to determine for sure where these
organic globules came from because they were simply too small. They are only
1/10,000 inch in size or less."
In 2005, two powerful new
nano-technology instruments were installed in the scientists' laboratory at Johnson Space Center.
The organic globules were first found in ultrathin slices of the meteorite with
a new JEOL transmission electron microscope. It provided detailed structural
and chemical information about the globules. The organic globules were then
analyzed for their isotopic compositions with a new mass spectrometer, the
Cameca NanoSIMS, the first instrument of its kind capable of making this key
measurement on such small objects.
The organic globules in the Tagish Lake
meteorites were found to have very unusual hydrogen and nitrogen isotopic
compositions, proving that the globules did not come from Earth.
"The isotopic ratios in
these globules show that they formed at temperatures of about -260° C, near
absolute zero," said Scott Messenger, NASA space scientist and co-author
of the paper. "The organic globules most likely originated in the cold
molecular cloud that gave birth to our Solar System, or at the outermost
reaches of the early Solar System."
The type of meteorite in which
the globules were found is also so fragile that it generally breaks up into
dust during its entry into Earth's atmosphere, scattering its organic contents
across a wide swath. "If, as we suspect, this type of meteorite has been
falling onto Earth throughout its entire history, then the Earth was seeded
with these organic globules at the same time life was first forming here."
said Mike Zolensky, NASA cosmic mineralogist and co-author of the paper.
The origin of life is one of the
fundamental unsolved problems in natural sciences. Some biologists think that
making a bubble-shape is the first step on the path to biotic life. "We
may be a step closer to knowing where our ancestors came from,"
Nakamura-Messenger said.
Image Credit: University Of Calgary
