The chemical seeds of Earthly life were planted by meteorites, says Columbia University chemist Ronald Breslow – and if it happened here, it could happen elsewhere.

In a report delivered to the American Chemical Society's annual meeting,

Breslow simulated the behavior of "left-handed" amino acids in an

Earth-like environment. The acids' appendage appellation derives from their molecular orientation, also known as chirality; except for a few oddball bacteria, all living creatures are composed of proteins made from left-handed amino acids. This phenomena has long perplexed scientists. Why left instead of right-handed? Why not both?

One possible explanation: because the first amino acids came from space, riding to Earth on meteorites. When the meteorites passed neutron stars, they were blasted with circular polarized light, in which photons corkscrew to either the left or right. Breslow's earlier experiments showed that CPL damages amino acids of corresponding handedness: if, on a fateful journey some four billion years ago, an Earthbound meteorite passed a star emitting right-spiraling CPL, it would have been stripped of right-handed acids, leaving the present orientation of life's building blocks as a biochemical echo of our extraterrestrial origin.

In his ACS report, Breslow added left-handed amino acids to the amino acid precursors found on pre-biotic Earth. The resulting acids were also left-handed and eventually dominated Breslow's mixture, suggesting that a similar process could have happened four billion years ago after a rock from space hit our hot and lifeless world.

Will we ever know for sure? Of course not. But it's plausible, and excesses of left-handed amino acids have indeed been found on meteorites landing in Australia and Tennessee during the last century.

Breslow next plans to study the origin of nucleic acids – the chemical units of DNA.

“This work is related to the probability that there is life somewhere else,” said Breslow in a press release. “Everything that is going on on

Earth occurred because the meteorites happened to land here. But they are obviously landing in other places. If there is another planet that has the water and all of the things that are needed for life, you should be able to get the same process rolling.”

Meteorites delivered the 'seeds' of Earth's left-hand life [press release]

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Image: Tobin*

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Note: I never feel good about quoting a press release, but in the blog world it's inevitable. At least I tell you when you're getting a canned quote. Wouldn't it be nice if other publications followed suit? *

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