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The Sciences

Did Life Begin In Space?

Interstellar organic molecules suggest that Earth may have been seeded by the cosmos.

By Kathryn GarfieldNovember 9, 2006 6:00 AM


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Interstellar clouds of gas are impregnated with organic molecules, the chemical ingredients of life. In just two years of work with the Robert C. Byrd Green Bank Telescope, astronomers have discovered eight new organic molecules near the center of the Milky Way, bolstering theories that key chemical precursors of life were first forged in deep space.

All eight of the new carbon-containing molecules are relatively large, composed of 6 to 11 atoms each. One of the molecules, acetamide, is particularly exciting because it contains a peptide bond, the essential bond for connections between amino acids. "No one has ever found an amino acid in space," says Jan M. Hollis of NASA's Goddard Space Flight Center. "I've actually written several papers about not finding them."

The new finds join a list of about 125 smaller carbon-based molecules identified in space so far. All of them tend to form by simple chemical reactions between smaller components or through the activity of radicals and neutral molecules on the surface of floating dust grains. Eventually, energy from nearby protostars causes the molecules to evaporate off the dust and fly end over end through space, where astronomers can trace their radiation frequencies, since each molecule radiates in a distinctive way.

In the famous Miller-Urey experiment of the 1950s, researchers produced a rich soup of amino acids by running an electric current through flasks containing elements of a primitive Earth, thus showing how precursor chemicals could have formed here. But the discovery of biologically significant molecules in interstellar clouds of gas and dust could push life's history much, much farther back in time and out into space. "When you look at these clouds, it's almost like looking back into history," Hollis says. Molecules like these, traveling on interplanetary dust, meteorites, or comets, "could give life a jump-start on an early planet."

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