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Astronomers Detect the Complex Molecules of Life in a Deep-Space Gas Cloud

The universe looks more and more like a friendly place for life to form.

by Michael Byrne
Sep 27 2014, 12:30pm

Life needs to be seeded. The universe just can't take any old set of molecules, mix them up in a primordial stew, and wait. It needs the right chemicals in the right places, molecules that are predisposed to evolve chemically into more and more complex structures, thus following a general pathway toward biology. If any old compound could find its way toward organic life, whether a methane steam or hunk of iron, the universe would be a disgusting ooze. The pathway for life as we know it starts with carbon.

A team of astronomers probing distant galaxies using the ALMA Observatory reported in this week's edition of Science the discovery of not just interstellar carbon, but carbon with a branched structure. Simple carbon chains aren't particularly unusual in the cosmos, but complex carbon is a different matter, what the researchers, based at Cornell University and the Max Planck Institute, describe as finding a molecular needle in a cosmic haystack—more specifically, the haystack of the gaseous star-forming region Sagittarius B2.

The actual molecule in question is isopropyl cyanide. It's possible to detect something like this with such precision mainly due to the wonders of radio astronomy. Within clouds of interstellar dust and gas, elements find themselves shielded from the harsh radiation of open space and are, thus, free to form into more complex arrangements (otherwise, it would be more likely that the molecule would be blasted apart before achieving complexity). These molecules don't just sit there, instead moving around within their cloud-homes and bumping into each other. The result of this activity are radio signals.

Every molecule has a different radio signal (different frequency), so it's possible to pick apart the contents of interstellar junk by examining a cloud's frequency spectra. NASA, via the Ames Research Center, even maintains a radio-emission frequency database to aid in the tracking of polycyclic aromatic hydrocarbons, a form of molecule thought to contain much of the universe's carbon stockpiles.

This detection suggests that branched carbon-chain molecules may be generally abundant in the interstellar medium.

The branching carbon structure of isopropyle cyanide is of particular interest because it's thought that this arrangement is a step on the way to the production of amino acids, the building blocks of proteins (among other things). The discovery gives weight to the increasingly popular notion that life, or at least many of the key steps leading toward life, actually occurs off-planet. Life on Earth may have been well on its way while the planet was still just space dust waiting to come together into our rock-home.

"[Isopropyle cyanide's] detection therefore bodes well for the presence in the [interstellar medium] (ISM) of amino acids, for which such side-chain structure is a key characteristic," the authors, led by astronomer Arnaud Belloche, write

What's more, the molecules discovered by the ALMA team probably aren't alone. "This detection suggests that branched carbon-chain molecules may be generally abundant in the [interstellar medium]," the paper continues.

The discovery follows a general progression in recent years adding more and more life-ingredients to our picture of the ISM. A 2011 study revealed that complex organic matter should be created in large volumes from stars, while a 2012 report study found that conditions within the ISM are uniquely suited to the creation of increasingly complex molecules, "step[s] along the path toward amino acids and nucleotides, the raw materials of proteins and DNA, respectively," reported.

Also in 2012, astronomers found basic sugar molecules hanging out in the gas cloud around a distant star. The particular form, glycoaldehyde, is thought to be a key component of the reaction behind the creation of DNA. Indeed, more and more, it's less a universe of life finding a way, than life's factory.

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