- Astronomers have a new take on what they once considered
lifeless outer space. They now think of our galaxy as a vast reactor for
biologically significant organic chemistry.
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- Materials that could jump-start organic evolution have
shown up in interstellar dust clouds and dusty planet-forming discs around
many stars. These findings fuel an increasingly strong suspicion that the
raw material of planet Earth was primed for life.
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- The infrared-sensing eyes of NASA's Spitzer Space Telescope
made the latest discovery. As NASA recently announced, Dan Watson and William
Forrest at the University of Rochester in New York found "significant
amounts of icy organic materials" around five young stars in Spitzer
data.
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- Water, methanol, and carbon dioxide coat dust particles
around these stars located 420 light-years away in the constellation Taurus.
NASA notes that, while such materials have been found elsewhere, "this
is the first time they were seen unambiguously in the dust making up planet-forming
gases."
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- Such discs appear to be common in our galaxy. Infrared
light penetrates dust, allowing astronomers to see into dusty areas. Spitzer
- launched last August - can image these areas with unprecedented clarity
and detail.
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- The telescope has been observing the nebula RCW 49, a
stellar nursery some 13,700 light-years away in the constellation Centaurus.
So far, it has provided early detailed data of discs around two of more
than 300 young stars.
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- The early data suggest all those stars have protoplanetary
discs, says Spitzer scientist Ed Churchwell from the University of Wisconsin
in Madison. "Spitzer has shown us that star and planet formation is
a very active process in our galaxy."
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- As data on interstellar chemicals have poured in over
the past decade, astronomers have abandoned their long-held prejudice against
such chemistry. They had thought that ultraviolet radiation from stars,
and other harsh conditions, would tear apart organic molecules even if
they did form.
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- However, dust can shield that chemistry. Many reactions
occur within protective icy coatings on dust particles. Some 130 organic
molecules have revealed themselves so far. They include such interesting
species as glycine, an amino acid; and ethylene glycol, the antifreeze
in your radiator.
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- Ethylene glycol is associated with formation of sugar
molecules necessary for life. It is what chemists call a reduced form of
the sugar glycolaldehyde. The research team that found the antifreeze also
detected this sugar in interstellar clouds.
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- "The discovery further demonstrates how important
interstellar chemistry may be in understanding the creation of biological
molecules on the Earth," said researcher Phillip R. Jewell when these
discoveries were reported in 2002. "Some scientists have even speculated
that the Earth could have been 'seeded' with complex molecules from passing
comets, which formed from the condensing gas nebula that produced our solar
system."
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- Discoveries since then have inspired some astrobiologists
to move from suspicion and speculation to at least mild conviction on this
point.
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- There is no consensus yet. But even skeptics find it
interesting that an interplanetary dust particle - snagged in the atmosphere
by a NASA aircraft - contains organic molecules that predate Earth.
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- Meanwhile, scientists are looking forward to the return
in January 2006 of the Stardust spacecraft, which has captured dust from
Comet Wild 2. Its sample containers may hold more decisive data.
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- Copyright © 2004 The Christian Science Monitor.
All rights reserved. http://www.csmonitor.com/2004/0617/p17s01-stss.html
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