Space Rocks Brought Life's Raw Material

Nobody knows how life on Earth began, but the primordialsoup likely got a lot of its ingredients from space.

Scientists have discovered concentrations of amino acids intwo meteorites that are more than ten times higher than levels previouslymeasured in other similar meteorites.

Amino acids are organic molecules that form the backbone ofproteins, which in turn build many of the structures and drive many of thechemical reactions inside living cells. The production of proteins is believedto constitute one of the first steps in the emergence of life. Meanwhile, meteoritesfound on Earth are typically chunks of material created in the solar system'syouth.

So the finding suggests that the early solar system was farricher in the organic building blocks of life than scientists had thought. Theresearchers speculate that rocks from space may have spiked Earth's primordialbroth.

It's an argument that's been made before.But the prevalence of amino acids strengthens the reasoning.

Scientists already knew amino acids could have formed insome environments on the early Earth, but the presence of these compounds incertain meteorites has led many researchers to look to space as a source.

The meteorites used for the study were collected in Antarcticain 1992 and 1995 and held in the meteorite collection at the NASA Johnson Space Center in Houston. Researchers took small samples from three rare CR chondrites,which date from the time of the solar system's formation. The rocks likely camefrom an asteroid that was long ago shattered.

"The amino acids probably formed within the parent bodybefore it broke up," said Conel Alexander of the Department of TerrestrialMagnetism at the Carnegie Institution. "For instance, ammonia and otherchemical precursors from the solar nebula, or even the interstellar medium,could have combined in the presence of water to make the amino acids. Then, afterthe break up, some of the fragments could have showered down onto the Earth andthe other terrestrial planets. These same precursors are likely to have beenpresent in other primitive bodies, such as comets, that were also rainingmaterial onto the early Earth."

The study will be detailed in the journal Meteoritics andPlanetary Science.

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