Racemization of Meteoritic Amino Acids

Barbara A. Cohen, Christopher F. Chyba

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Meteorites may have contributed amino acids to the prebiotic Earth, affecting the global ratio of right-handed to left-handed (D/L) molecules. We calculate D/L ratios for seven biological, α-hydrogen, protein amino acids over a variety of plausible parent body thermal histories, based on meteorite evidence and asteroid modeling. We show that amino acids in meteorites do not necessarily undergo complete racemization by the time they are recovered on Earth. If the mechanism of amino acid formation imposes some enantiomeric preference on the amino acids, a chiral signature can be retained through the entire history of the meteorite. Original enantiomeric excesses in meteorites such as Murchison, which have undergone apparently short and cool alteration scenarios, should have persisted to the present time. Of the seven amino acids for which relevant data are available, we expect glutamic acid, isoleucine, and valine, respectively, to be the most likely to retain an initial enantiomeric excess, and phenylalanine, aspartic acid, and alanine the least. Were the D/L ratio initially identical in each amino acid, final D/L ratios could be used to constrain the initial ratio and the thermal history experienced by the whole suite.

Original languageEnglish (US)
Pages (from-to)272-281
Number of pages10
Issue number1
StatePublished - May 2000
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Exobiology
  • Meteorites
  • Organic chemistry
  • Prebiotic chemistry
  • Prebiotic environments


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