New York: Astronomers claim to have found an amino acid on a comet for the first time, a discovery which confirms that some of life's building blocks were delivered to the early Earth from space.
Amino acids are crucial to life because they form the basis of proteins, the molecules that run cells. They form when organic, carbon-containing compounds and water are zapped with a source of energy, such as photons -- a process that can take place on Earth or in space.
Previously, amino acids have been found in space rocks that fell to Earth as meteorites. Now, a team at NASA Goddard Space Flight Center have analysed samples from the agency's Stardust mission and traced the amino acid called glycine to an icy comet for the first time, the 'New Scientist' reported. "It's not necessarily surprising, but it's very satisfying to find it there because it hasn't been observed before. It's been looked for (on comets) spectroscopically with telescopes but the content seems so low you can't see it that way," lead astronomer Jamie Elsila said.
According to the astronomers, comets and asteroids are thought to have bombarded the Earth early in its history, and the new discovery suggests they carried amino acids with them. "We are interested in understanding what was on the early Earth when life got started. We don't know how life got started... but this adds to our knowledge of the ingredient pool," Elsila said.
The amino acid was found in samples returned to Earth by NASA's Stardust mission, which flew by Comet Wild 2 in 2004 to capture particles shed by the five-kilometre object. "There might be more complex mixtures (of amino acids) and higher levels of them in a comet nucleus," Elsila said.
The findings are published in the latest edition of the 'Meteoritics & Planetary Science' journal.