The molecular orientation of compounds brought to Earth by meteorites could have determined the world's chemistry long before life began, according to a new linkurl:study;http://www.pnas.org/cgi/doi/10.1073/pnas.0811618106 published online today (Mar. 16) in the __Proceedings of the National Academy of Sciences__.
Amino acids come in left-handed and right-handed forms, which, like a pair of human hands, are mirror images that cannot be superimposed onto each other. Yet living organisms use only the left-handed version, which presents a conundrum: There's no biochemical reason why one mirror image should be better than the other, so scientists have long debated whether life's left-handed leaning arose because of random processes or whether rocks from outer space seeded a southpaw solar system. The current study argues for the latter possibility by showing that some extraterrestrial meteorites contain an abundance of left-handed molecules....
left-handedness (click to enlarge)
Image: NASA/Pat Rawlings
Image: US Department of Energy
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