Building block: The structure of amino acetonitrile - a precursor to the amino acid glycine found in deep space.

Credit: Sven Thorwirth, MPIfR

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SYDNEY: Astronomers have for the first time detected a complex precursor to an amino acid in deep space, bringing us closer to finding key ingredients critical to the development of life.

Amino acids are of great interest to radio astronomers as they are the building blocks of proteins. Finding them in space would increase the chances that life has evolved elsewhere.

Although amino acids have been detected in meteorites, astronomers have unsuccessfully scanned the void of space for the elusive compounds for over 30 years. While numerous searches have been made for interstellar glycine (the simplest amino acid), so far all claims for its detection have been subsequently disproved. The most recent claim was made by a team at the National Taiwan Normal University in 2003 but has since been persuasively rebutted.

Best evidence yet

Now scientists from the Max Planck Institute for Radio Astronomy in Bonn, Germany, have focused their search on a molecule called amino acetonitrile, which is thought to be a direct precursor of glycine.

The international team, led by astrophysicist Arnaud Belloche, used a 30-metre radio telescope at Pico Veleta in the Sierra Nevada mountains of southern Spain. They pointed it at the Large Molecule Heimat, a giant gas cloud near the galactic centre in the constellation Sagittarius. Their results are slated for publication in the journal Astronomy & Astrophysics.

To find the organic molecules emanating from gas clouds and the gas envelopes surrounding newborn stars astronomers analyse the spectral lines in the millimetre and sub-millimetre wavelengths of the electromagnetic spectrum. More than 140 organic molecules have been found in space using this method to date, many in the hot, dense gas clump of the Large Molecule Heimat.

Organic molecules, such as amino acids, garner special attention because they are likely ingredients in the primordial soup that led to the development of life on Earth. However, reliably recognising the tell-tale signals of such complicated molecules has proved extremely difficult, since the signals from complicated molecules are numerous and weak.

Glycine forming

"Still, we were finally able to assign 51 very weak lines to the molecule amino acetonitrile," says Belloche. His group confirmed their results by collecting additional data using the Plateau de Bure interferometer, a six-dish array in the French Alps and the six 22-metre dishes of the Australia Telescope Compact Array in Narrabi in New South Wales.

The team believe that amino acetonitrile forms on the surface of grains of ice in the gas cloud and could potentially react with water to create glycine. It's also possible that amino acids themselves may be present, said Belloche, but their spectral signatures may be beyond the team's current search capability and therefore invisible.

Karl Menten, director of the Max Planck Institute for Radio Astronomy said that finding amino acetonitrile has already improved astronomers' understanding of 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" he added. "We already have several candidates."