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Biological Chemistry

Meteorite Provides Hints About Life’s Handedness

Water inside celestial objects possibly sparked dominant handedness in amino acids on Earth

by Carmen Drahl
August 13, 2012 | APPEARED IN VOLUME 90, ISSUE 33

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Credit: Michael Holly/U of Alberta
This fragment of the Tagish Lake meteorite has been kept in the cold since it crashed into the frozen lake in 2000.
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Credit: Michael Holly/U of Alberta
This fragment of the Tagish Lake meteorite has been kept in the cold since it crashed into the frozen lake in 2000.

By examining meteorite fragments, researchers have provided support for the idea that chiral amino acids essential to life on Earth originated by amplification of small enantiomeric excesses of the molecules (Meteorit. Planet. Sci., DOI: 10.1111/j.1945-5100.2012.01400.x). Daniel P. Glavin of NASA’s Goddard Space Flight Center and colleagues analyzed bits of the Tagish Lake meteorite, which crashed into the frozen surface of the Canadian lake in 2000. They found a large excess of l-aspartic acid and verified through carbon isotope measurements that the enrichment was not the result of any earthly contamination. It’s possible that water in the celestial body, present in liquid form in space as a result of heat given off from radioactivity, led to amplification of a small initial l-aspartic acid excess through crystallization, a process other groups have demonstrated experimentally, explains coauthor Aaron S. Burton. l-Alanine in the meteorite was not amplified, a result that can be explained by different crystallization behavior, he adds. Richard M. Kellogg of Dutch custom chemicals firm Syncom, an expert in homochirality, praises the work but notes that l-aspartic acid could also have been amplified by sublimation in ice.

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