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An Excess of Enantiomers in Primitive Meteorites
A cross section of the Allende meteorite, the largest carbonaceous chondrite meteorite ever found on Earth. Credit: NASA GSFC

Astrobiologists at the University of Arizona and Arizona State University have performed a comprehensive analysis of the organic composition of ancient asteroidal remnants that fell to Earth called carbonaceous chondrites (CRs). CRs are unique in that, once having been part of asteroids, they have avoided the geological reprocessing that larger planets and moons have undergone, thus preserving a record of the conditions of the early solar system. Studying these materials is like experiencing time travel!

The study, published recently in PNAS, shows that several CR compounds, including amino acids, show no or minimal exposure to water. The team also analyzed the relative amounts of both left-handed and right-handed versions of the amino acids within the CRs. On Earth, many of the molecules used by life, like amino acids, are found primarily in their left-handed form. The team concludes that the presence of water in CR fragments has a strong effect on selecting whether or not right- or left-handed molecules are ultimately present in the material. Understanding how and why the dominance of left-handed molecules developed is important for astrobiologists studying the origins of life.

Source: Arizona State University

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