"Amino acids are certainly one of the key components of terrestrial life. That's why it was such a momentous development in 1952 when Stanley Miller and Harold Urey were able to produce them in the lab using electrical discharges in mixes of methane, ammonia, hydrogen and water," Brownlee said.
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"We still don't know if the organic materials needed to form life were created on Earth or fell in from space," he added. "Meteorites and now comets prove that Earth has been seeded with many critical biomolecules over its entire history."
And not just Earth. The new study, published in this week's Science Advances, suggests glycine is a common ingredient in star- and planet-forming regions beyond the solar system.
"Amino acids are everywhere," said Rosetta scientist Kathrin Altwegg, with the University of Bern in Switzerland. "Life could possibly also start in many places in the universe."
"Although the researchers from Stardust did a very good job with their data, I think it's important to confirm their findings by measuring amino acids right in the coma -- the gas and dust cloud surrounding the comet -- without having to be afraid of terrestrial contamination," Altwegg wrote in an email to DNews.
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Having found glycine in more than one comet shows that neither Wild 2 nor 67P are exceptions, she added.
Altwegg, lead author of the new paper, and colleagues also detected phosphorus, a key element in all living organisms and the backbone of DNA and RNA. No phosphorus was found in the Stardust grains.
"The presence of glycine, phosphorus, and a multitude of organic molecules, including hydrogen sulfide and hydrogen cyanide, seen in the coma of 67P/Churyumov-Gerasimenko supports the idea that comets delivered key molecules for prebiotic chemistry throughout the solar system and, in particular, to the early Earth, drastically increasing the concentration of life-related chemicals by impact on a closed-water body," the scientists write in the study.
Rosetta is expected to continue to look for complex organic molecules during the four months remaining in its mission.