Was the early Earth seeded with amino acids from deep space? The variety of molecules found between the stars makes the supposition provocative, but finding interstellar amino acids has been a challenge. Various amino acids have indeed been found in meteorites, but it has been argued that these could have been produced right here in the Solar System within asteroids. Yet laboratory experiments have shown that amino acids can form among the molecules found in interstellar clouds, including such important ones as glycine, alanine and serine.
What’s next is to identify amino acids in the interstellar medium, and we’re coming close. Ponder this: Since 1965, more than 140 molecules have been identified in space, both in interstellar clouds and circumstellar disks, many of them organic or carbon-based. Now researchers from the Max Planck Institute for Radio Astronomy in Bonn have detected amino acetonitrile (NH2CH2CN), a potential precursor of the simplest amino acid, glycine. The odds are rising that the processes that spread life are commonplace: Stars and planets forming within interstellar clouds where amino acids can be found would be subject to infalls of these materials, perhaps enhancing the chances of life elsewhere in the universe. (Addendum: I’ve added the ‘perhaps’ in that sentence as a result of the interesting comment thread that has developed on this topic; see below).
The focus of the Bonn team’s investigations has been Sagittarius B2. Located about 100 parsecs (326 light years) from galactic center, and some 8000 parsecs from Earth, this is a highly active region of star formation — massive, complex, and packed with interesting chemistry. Sagittarius B2 is composed of two dense cores of star formation separated by two parsecs, one of which is possessed of a chemistry so rich that it has been christened the Large Molecule Heimat (LMH) because of the numerous detections of complex molecules made there.
The Bonn team analyzed 3700 spectral lines from complex molecules using the IRAM 30-metre telescope in Spain, with results confirmed by instruments in France and Australia. The Institute’s Karl Menten sees the discovery as a sign of progress in our understanding of the regions where stars are born:
“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!”
Such molecules emit hundreds of weak spectral lines, producing spectra so crowded that untangling the components is an extraordinary challenge. And while the hunt for glycine has had a long and inconclusive history, the identification of amino acetonitrile gives us a molecule chemically related to glycine, one whose status as an amino acid precursor is argued in the paper on this work. Conclusive proof of amino acids in interstellar clouds seems closer than ever, an indication that life’s building blocks may predate the formation of the systems they seed.
The paper is Belloche et al., “Detection of amino acetonitrile in Sgr B2(N),” accepted by Astronomy & Astrophysics and available online.