[meteorite-list] Amino Acids Detected In Space

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:16:32 2004
Message-ID: <200308121552.IAA08122_at_zagami.jpl.nasa.gov>

http://physicsweb.org/article/news/7/8/7

Amino acid detected in space
Matthew Chalmers
Physics Web
11 August 2003

The idea that primitive life on Earth may have been seeded by a comet or
asteroid impact is controversial. Since it was suggested more than 40 years
ago, however, increasingly complex organic molecules have been discovered
in space. Now astronomers have detected an amino acid - one of the building
blocks of proteins - in interstellar dust clouds in our galaxy. The discovery of
glycine in space suggests that interstellar molecules may have played a pivotal
role in the prebiotic chemistry of the Earth (Y-J Kuan et al. 2003 Astrophys. J.
593 848).

Glycine - CH2NH2COOH - is the simplest of all the 20 amino acids. Yi-Jehng
Kuan of the National Taiwan Normal University and co-workers from the NASA
Ames Research Center and the Polish Academy of Sciences searched for the
molecule in the hot cores of three giant molecular clouds, which are regions of active
star formation. They measured the spectral lines of the clouds - Sagittarius-B2,
Orion-KL and W51 - over a four-year period using the 12-metre telescope at the
National Radio Astronomy Observatory (NRAO) in Arizona.

The frequencies of certain transitions in glycine, which are known from experiments
in the lab, provide a characteristic signature for the molecule. Knowing this spectral
"fingerprint", the researchers were able to identify 27 glycine lines at frequencies
between 90 and 265 GHz in the clouds. This confirms the results of earlier searches
for interstellar glycine in which tantalizing evidence was provided by a handful of
spectral lines.

Observing the spectral lines in these clouds - which are tens of thousand of
light-years away - is not easy because the lines are very weak. Moreover, the
molecular transitions that cause them can be contaminated by emissions from
"interloper" molecules in the surrounding medium. To overcome these difficulties,
Kuan and co-workers concentrated on high-frequency molecular transitions that
occur in warm, dense regions of the clouds. The chemical process that actually
produces glycine in the interstellar medium is not understood, although lab-based
experiments suggest that amino acids can be created by exposing organic molecules
in interstellar ice to ultraviolet radiation.

The researchers claim that the discovery of glycine is the first step in establishing
the crucial link between amino acids in space and the emergence of life in the solar
system or, indeed, elsewhere in the galaxy. The molecular spectra seen in
interstellar gas clouds closely matches those found in comets and meteorites, and
comparing them could in principle allow astronomers - or exobiologists - to trace
the origin of the Earth's early chemistry to its parent gas cloud.

Author
Matthew Chalmers is Features Editor of Physics World
Received on Tue 12 Aug 2003 11:52:18 AM PDT