Fetched from a faraway comet, distinctive amino acids

In the vapors surrounding a comet millions of miles away, scientists claim to have found amino acids - one of the basic building blocks of life.

The find came from a mission called Stardust - the first since Apollo 17 more than 30 years ago to return a sample of anything from space. The Stardust craft was launched in 1999, and got within a few miles of its target, a comet called Wild 2, in 2004.

Using a Frisbee-sized trap made from a soft, porous substance called aerogel, it scooped up just a pinch of comet dust. But this tiny haul could hold a wealth of information about the formation of the solar system and perhaps the origin of life.

When the craft was launched, many scientists suspected that comets brought amino acids and other life-building molecules to Earth. Our planet was too hot during its formation to have preserved such fragile molecules.

Amino acids have also turned up in meteorites - and reportedly lent a distinctive smell to pieces of the famous Murchison meteorite, which fell on Australia.

Stardust landed in Utah in 2006, its sample intact. It took two years of analysis to prove the amino acid they found, called glycine, didn't come from earthly contamination. The researchers were able to make the distinction because space molecules are known to carry a higher percentage of a heavy form of carbon called carbon-13.

"We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet," said NASA-Goddard astrophysicist Jamie Elsila, lead author on the paper announcing the find.

The findings add to a body of evidence that the raw materials of life are sprinkled through the outer solar system, and possibly through other solar systems as well.