Scientists have uncovered fresh evidence that life could exist beyond Earth, with research published showing that comet dust contained traces of a compound vital to human existence.
Researchers probing dust and gas collected from the Wild 2 comet by NASA's Stardust spacecraft in 2004 found traces of the amino acid glycine, lending credence to idea that there is life elsewhere in the universe.
"The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare," said Carl Pilcher, one of the space agency's top astrobiologists.
Jamie Elsila, lead author of the report, which was published in the journal Meteoritics and Planetary Science, said the findings also support the idea that the material elements of human life may have come from space.
"Our discovery supports the theory that some of life's ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts," she said.
The group's final findings confirm suspicions that the amino acid -- which creates the proteins that form the building blocks of life -- were not simply earth-sourced contamination.
"We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet," said Elsila.
Twenty different amino acids are arranged to build the millions of different proteins that make up everything from hair to enzymes, NASA said.