WET rocks hurtling around the solar system may have given life on Earth its addiction to left-handed building blocks.
Almost all life on Earth uses left-handed amino acid molecules instead of their right-handed counterparts. In the 1990s, scientists found that meteorites contain up to 15 per cent more of the left-handed versions too. So space rocks bombarding the early Earth may have biased the planet鈥檚 chemistry. A linked theory has it that polarised starlight can preferentially destroy right-handed amino acids on asteroids, though this alone cannot explain the strength of the bias on meteorites.
Now and of NASA鈥檚 Goddard Space Flight Center in Greenbelt, Maryland, have shown that water amplifies the bias. They studied an amino acid called isovaline in six meteorites that showed ancient evidence of 1000 to 10,000 years鈥� exposure to liquid water. The longer water persisted in the rock, the stronger its left-handed isovaline bias, the pair found (Proceedings of the National Academy of Sciences, ).
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