A piece of the Murchison meteorite. © New England Meteoritical Services.
The Murchison meteorite is a carbonaceous chondrite which exploded into fragments over the town of Murchison, approximately 200 km north of Melbourne in Victoria, Australia, on September 28, 1969. About 82 kg of the meteorite was recovered.
Eyewitnesses arriving at the scene reported smelling something like methanol or pyridine, an early indication that the object might contain organic material. Subsequent analysis by NASA scientists and a group led by Cyril Ponnamperuma revealed the presence of 6 amino acids commonly found in protein and 12 that did not occur in terrestrial life. All of these amino acids appeared in both dextrorotatory (right-handed) and levorotatory (left-handed) forms, suggesting that they were not the result of Earthly contamination. The meteorite also contained hydrocarbons which appeared abiogenic in character and was enriched with a heavy isotope of carbon, confirming the extraterrestrial origin of its organics. Initial studies suggested that the amino acids in the Murchison meteorite showed no bias between left- and right-handed forms. However, in 1997, John R. Cronin and Sandra Pizzarello of Arizona State University reported finding excesses of left-handed versions of four amino acids ranging from 7 to 9%,1 a result confirmed independently by another group.2 Altogether 92 different amino acids have been identified in Murchison, only 19 of which are found on Earth. To this organic mixture, in 2001, was added a range of polyols – organic substances closely related to sugars such as glucose.3
1. Cronin, J. R., and Pizzarello, S. "Enantiomeric Excesses in Meteoritic
Amino Acids," Science, 275, 951 (1997).
2. Engel, M. H., and Macko, S. A. "Isotopic Evidence for Extraterrestrial Non-Racemic Amino Acids in the Murchison Meteorite," Nature, 389, 265 (1997).
3. Cooper, G. et al. "Carbonaceous meteorites as a source of sugar-related organic compounds for the early Earth," Nature, 414, 879-883 (2001).