Comet Tail with Glycine Amino Acid Amazes All
Amino Acid Presence Indicates Extraterrestrial Organic Molecules
Sep 3, 2009
The first successful capture and return to earth of comet debris has amazed scientists. Among the expected inorganic chemicals, the organic amino acid glycine was detected — glycine was like a giant pearl in an oyster. What does this glycine story really mean?
Telescopes, Comets, and Spacecraft Capture and Retrieval Merge in the Stardust Project
Telescopes are excellent research tools and reveal much about space. Comets are among the rhythmic, predictable visitors that streak across the sky, and comets can be photographed and instrumentally-studied by astronomers. The Stardust project was a bold venture of extending a scientific hand into space to touch and retrieve a comet's tail — it worked!
The Wild 2 comet has an orbital period of 6.39 years compared to the 2,320 year periodicity of the Hale-Bopp comet last seen in 1997. The Goddard Space Center Stardust team decided Wild 2 was an ideal candidate for a "Stardust" spacecraft comet-sampling encounter.
Capture of Molecules, Compounds and Materials in Outer Space
Capture of comet materials requires precise spacecraft guidance and execution to intersect with a comet's orbit. This spacecraft's total journey of 3.2 billion miles achieved a successful intersection of the orbit, capture of valuable comet samples, and a triumphant return of the spacecraft to earth's orbit .
"Stardust" on January 2, 2004 came within 150 miles of the comet. Comet debris surrounded the the icy nucleus of Wild 2 (pronounced "Vilt-2") and "Stardust" began to collect samples from the comet's debris field on foil and a sponge-like aerogel grid . Two years later the spacecraft returned and neared earth. The grid, stowed in a capsule, was detached from the spacecraft and parachuted to Earth on January 15, 2006. Many scientists began critical analyses of comet samples to determine the characteristics of the comet and possible clues to the history of our solar system.
Glycine Amino Acid Found in Comet Dust and A Critical Experiment
The presence of the amino acid glycine, in foil and the aerogel, was initially confirmed by the Goddard Space lab. However, it was necessary to rule out earthly glycine contamination. This was done by using the foil for glycine analysis. On earth, Carbon 12 is more common than Carbon 13, the latter isotope of carbon is heavier due to one extra neutron. The glycine from the spacecraft foil sample showed a preponderance of C-13, not C-12, and this strongly indicated that the space material was extraterrestrial.
The Stardust research team at Goddard includes Drs. Brownlee of the University of Washington and Elsila, Glavin, Dworkin, of Goddard Space Center, NASA. They believe that the foil and aerogel results suggest that much of the Stardust's comet-exposed side and the collection grid was coated by glycine that was formed in space.
Space and Extraterrestrial Life, Organic and Molecular Speculations
It is important to remember that glycine is only one of the 20 natural amino acids. No other amino acids have been discovered in the comet material as of this time.
Active proteins and enzymes from living cells contain many, or all of the 20 known amino acids. So, although this was an exciting and interesting comet study and find of glycine, important questions arise. Can other, more complex amino acids be detected? Is there any evidence of prokaryotic life somewhere in the vastness of space? How and where can science best explore and sample for life next?
Scientists and all are left to wonder. Many feel that planet earth's life forms are not the only ones, and that in other galaxies and planets far away there is life. Glycine provides only a tiny link to this thinking — but it is a link, and a beginning!
A simple telescope carries the mind and imagination far beyond the earthly stand the telescope rests upon.
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Resource
Garlick, M.A. 2007. Atlas of the Universe. Weldon Owen Pty Ltd., Sydney, Australia. 304 pp
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