Physical Sciences: Evidence for Amino-acids of Extraterrestrial Origin in the Orgueil Meteorite

Abstract

THE Orgueil meteorite¹, a Type I carbonaceous chondrite that fell in France in 1864, has a high carbon content of about 5 per cent. It has been reported to contain several organic compounds, but some of these compounds, notably amino-acids^2–4, have been suspected of being terrestrial contaminants^4–7. Until recently it has been difficult to determine the extent of the contamination which occurred between the time of fall of a meteorite and its examination in the laboratory. Now, however, the problems of separation of contaminant from indigenous amino-acids in meteorites can be largely overcome by applying gas chromatographic techniques for the separation of D, L enantiomers of amino-acids as their diastereomeric derivatives and the identification of these compounds by gas chromatographic retention times and mass spectral fragmentation patterns. This kind of approach has been used in investigations of the amino-acids in the Murchison and Murray meteorites^8–11. Because terrestrial, biogenic amino-acids are commonly of the L configuration, the presence in these meteorites of racemic mixtures of D, L amino-acids suggested a nonbiogenic origin for these compounds. In addition, the presence of amino-acids not commonly found in protein also strongly implied an extraterrestrial, abiotic origin.