NASA boffins say that they have identified an amino acid, one of the key building blocks of Earth-style life, in material recovered from a comet far out in space. They say this supports the idea that life may be commonly found throughout the universe, and that they have eliminated the chance that the cometary sample has been contaminated by Earthly life.
The sample in question was scooped from the comet Wild-2 in 2004 by the NASA space probe Stardust, which was launched a decade ago in 1999. Having made a close pass to the comet and picked up some of its substance, Stardust then dropped the sample capsule back to Earth in 2006. The main probe, remaining in space, is now to head out again to investigate the comet Tempel-1.
Meanwhile on Earth, boffins analysing the returned "aerogel" collectors soon discovered traces of glycine, an amino acid used by earthly life in building up proteins.
However, "it was possible that the glycine we found originated from handling or manufacture of the Stardust spacecraft itself," according to NASA's Dr Jamie Elsila. The scientists have since carried out isotopic analysis of the carbon in the sample, finding that it contains too much carbon-13 to be from Earth.
"We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet," says Elsila. In his view, this signifies that the basic chemicals from which life can arise may be commonly found beyond the solar system, suggesting that life would be more likely to arise on other worlds.
"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," says Dr Carl Pilcher, Director of the NASA Astrobiology Institute.
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