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Finding More Organics in Space
Based on an Max Planck Society news release
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Cosmic Evolution
Posted:   03/27/08

Summary: Researchers have detected a molecule closely related to an amino acid at the center of our Milky Way Galaxy. The finding provides more evidence that precursor molecules important for the origin of life can be found in interstellar space.

Scientists Detect Amino Acetonitrile near the Center of our Milky Way

Amino Acids have been found in meteorites on Earth, like the Murchison meteorite (above). However, these important molecules for life have not yet been directly observed in interstellar space.
Credit: NASA

Researchers from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn have detected for the first time a molecule closely related to an amino acid: amino acetonitrile. The organic molecule was found with a 30 metre radiotelescope in Spain and two radio interferometers in France and Australia in the "Large Molecule Heimat", a giant gas cloud near the galactic centre in the constellation Sagittarius (Astronomy & Astrophysics, in press).

The "Large Molecule Heimat" is a very dense, hot gas clump within the star forming region Sagittarius B2. In this source of only 0,3 light-year diameter, which is heated by a deeply embedded newly formed star, most of the interstellar molecules known to date have been found, including the most complex ones such as ethyl alcohol, formaldehyde, formic acid, acetic acid, glycol aldehyde (a basic sugar), and ethylene glycol.

Observations were made using the IRAM 30-metre telescope in Spain.
Credit: Institut de Radio Astronomie Millimétrique

Starting from 1965, more than 140 molecular species have been detected in space, in interstellar clouds as well as in circumstellar envelopes. A large fraction of these molecules is organic or carbon-based. A lot of attention is given to the quest for so-called "bio"-molecules, especially interstellar amino acids. Amino acids, the building blocks of proteins and therefore key ingredients for the origin of life, have been found in meteorites on Earth, but not yet in interstellar space.

The simplest amino acid, glycine (NH_2 CH_2 COOH), has long been searched for in the interstellar medium but has so far not been unambiguously detected. Since the search for glycine has turned out to be extremely difficult, a chemically related molecule was searched for, amino acetonitrile (NH_2 CH_2 CN), probably a direct precursor of glycine.

Astronomers observed a hot gas clump within the star forming region Sagittarius B2 (above).
Credit: NASA

The scientists from the Max Planck Institute for Radioastronomy in Bonn selected the "Large Molecule Heimat", as the source has been named by experts, and investigated a dense forest of 3700 spectral lines from complex molecules with the IRAM 30-metre telescope in Spain. Atoms and molecules emit light at very specific frequencies, which appear as characteristic lines in the radiation spectrum. By analyzing these spectral lines, astronomers can determine the chemical composition of cosmic clouds. The more complex a molecule is, the more possibilities it has to radiate its internal energy. This is the reason why complex molecules emit many spectral lines, which are very weak and therefore difficult to identify in the "line jungle".

"Still, we were finally able to assign 51 very weak lines to the molecule amino acetonitrile" says Arnaud Belloche, scientist at the Max Planck institute and first author of the research paper. This result was confirmed at 10 times higher spatial resolution with two radiotelescope arrays, the IRAM Plateau de Bure interferometer in France and the Australia Telescope Compact Array. These observations showed that all the candidate lines were emitted from the same position in the "Large Molecule Heimat", "a strong proof of the reliability of our identification".

Many of the ingredients for life formed in outer space. The Earth formed from star dust, and later meteorites and comets delivered even more materials to our planet. But scientists are still unsure which molecules played the most important roles in life's origin.
Credit: European Space Agency

"Finding amino acetonitrile has greatly extended our insight into the chemistry of dense, hot star-forming regions. I am sure we will be able to identify in the future many new, even more complex organic molecules in the interstellar gas. We already have several candidates!", says Karl Menten, director at the Max Planck Institute for Radioastronomy and head of the "Millimeter and Submillimeter" research group.


Related Web Sites

Astrobiology Roadmap Goal 3: Origins of Life
Building Life from Star Stuff
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We Are All Made of Stars
First Images Show Organic Molecules
Amino Acid Ingredients Found in Distant Galaxy


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