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Outer
Space Not So Lifeless After All
By
Robert C. Cowen The Christian Science Monitor. 6-18-4
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.
 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.
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.
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."
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.
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.
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."
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.
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.
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
.
"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."
Discoveries since then have inspired some astrobiologists
to move from suspicion and speculation to at least
mild conviction on this point.
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.
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.
2004 The Christian Science Monitor. All rights reserved.
http://www.csmonitor.com/
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