Orgueil, 1.68 g with small fragments (ex MNHN, Paris). Image Source:

A large carbonaceous Ivuna-like (CI1) chondrite that disintegrated and fell in fragments near the French town of Orgueil on May 14, 1864. About 20 pieces, totaling ~12 kg in mass, were subsequently recovered from an area of several square km, some head-sized but most were smaller than a fist. Specimens could be cut with a knife and, when sharpened, pieces could be used like pencils.

In 2001, researchers found that a pristine piece of the interior of Orgueil contained a relatively simple mixture of amino acids, consisting primarily of glycine and β-alanine. They also analyzed the sample’s carbon isotope concentration and found that the amino acids were not derived from Earthly contamination but instead were almost certainly synthesized chemically in space. The research team then compared their results with three other meteorites: Murchison and Murray, which have been studied extensively, and Ivuna, a meteorite that fell in Tanzania, Africa, in 1938, that had not been analyzed for amino acids. The team broke the meteorites down into two classes.The Murchison and Murray meteorites were placed in a category containing a complex mix of amino acids made up of more than 70 different types of amino acids. Orgueil and Ivuna, however, were categorized with a much simpler composition made up primarily of just two amino acids.

Murchison and Murray are widely believed to be pieces of an asteroid, as are virtually all meteorites scientists have studied. However, Orgueil and Ivuna show evidence that they are derived from a comet. The amino acid signatures within Orgueil and Ivuna suggest that these compounds were likely synthesized from components such as hydrogen cyanide, which have been recently observed in the comets Hale-Bopp and Hyakutake. This suggests that the organic material in Orgueil and Ivuna is the product of reactions that once took place in the nucleus of a comet, which, if true, would make these meteorites the first to be identified as having come from a comet nucleus.

Some or all content above used with permission from J. H. Wittke.