Comet Holds Building Block for Life

An amino acid, one of the essential ingredients to life on Earth, has been found in a comet for the first time, NASA announced Monday.

Since amino acids have already been discovered in meteorites, this new development, reported at the American Chemical Society meeting in Washington, D.C., suggests that early Earth had plenty of opportunities to have been seeded for life by extraterrestrial bodies.

Scientists concluded nearly two years of painstaking research on comet samples returned by the Stardust probe to confirm that glycine -- one of 20 known amino acids that form the building blocks for life on Earth -- was in the comet Wild 2, and not the result of terrestrial contamination.

"We're interested in understanding the inventory of materials that were available on early Earth when life got started," lead researcher Jamie Elsila, with NASA's Goddard Space Flight Center in Greenbelt, Md., told Discovery News.

"It's not a particularly unexpected discovery that glycine is in a comet -- we've found amino acids in meteorites before -- but it does show that comets are another way that amino acids could have come to Earth," she said.

Elsila and colleagues developed a technique to extract and analyze deposits of glycine from bits of aluminum foil that lined the probe's collection plates. They discovered that carbon atoms in the glycine had an extra neutron in its nucleus compared to terrestrial carbon, confirming that the amino acid did not come from Earth.

"This is telling us that the molecular ingredients for life are ubiquitous," Carl Pilcher, who oversees NASA's astrobiology program at the Ames Research Center in Mountain View, Calif., told Discovery News.