Researchers Have Found Traces of the Amino Acid Glycine in Comet Wild 2

Wired Science Blog reports that: "Scientists have discovered the amino acid glycine, a critical component of all living things, hiding in samples from the comet Wild 2.

"It’s the first time an amino acid has been found inside a comet, and NASA scientists say the discovery supports the theory that some of the ingredients necessary for life originated in space and traveled to Earth by comet or meteorite.

“If you’re seeing amino acids in comets, then that really gives credence to the idea that the basic components of life are going to be widespread throughout the universe,” said planetary biologist Max Bernstein of the NASA Astrobiology Institute, who was not involved in the research. “It’s one thing for me to do it in the lab and say it should be so, but it’s another thing for somebody to actually measure it.”

"Glycine was isolated from tiny samples of material collected from Wild 2 in 2004 by the NASA spacecraft Stardust. As the spacecraft flew through dense clouds of gas and dust surrounding the comet's nucleus, a container of aerogel trapped particles from the comet. Since the aerogel capsule was parachuted to Earth in 2006, scientists have been racing to analyze the contents of the collected samples. Although preliminary reports indicated traces of glycine in the aerogel, researchers didn't have enough aerogel sample to determine whether the amino acid was an Earthly contaminant or had truly come from space.

"To get enough glycine for their analysis, the scientists actually analyzed the aluminum foil that lined the inside of the aerogel collection grid. Volatile gas particles had diffused through the aerogel and gotten stuck to the foil — but even the foil provided only a half a nanomole of glycine to work with, and it took the researchers two years to confirm that the glycine had extraterrestrial origins.

"What we did was look at the carbon isotopes," said NASA scientist Jamie Elsila, who presented the work Sunday at the American Chemical Society meeting in Washington D.C. "The stuff on the Earth has a special signature, and the extraterrestrial signature is very different. When we looked at glycine and measured its carbon signature, we saw that it's in the extraterrestrial range."

"Elsila says the extraterrestrial glycine may have formed inside the comet when UV light hit the molecular precursors and caused them to react. Researchers say this provides some of the best evidence thus far that the precursors for life may have originated in outer space. "We don't know how life originated on the early Earth," Elsila said. "But we have a pretty good idea that the comets and meteorites that bombarded the early Earth provided a lot of the material."

Image: 1) Artist's rendering of the Stardust spacecraft as it approached the Wild 2 comet, NASA/JPL. 2) Tracks of comet particles in aerogel, NASA.