Orgueil (meteorite) - Composition and Classification

Composition and Classification

Orgueil is one of five known meteorites belonging to the CI chondrite group (see meteorites classification), this being the largest (14 kg). This group is remarkable for having a composition that is essentially identical to that of the sun, excluding gaseous elements like hydrogen and helium.

Because of its extraordinarily primitive composition and relatively large mass, Orgueil is one of the most-studied meteorites. One notable discovery in Orgueil was a high concentration of isotopically anomalous xenon called "xenon-HL". The carrier of this gas is extremely fine-grained diamond dust that is older than the solar system itself, known as presolar grains.

In 1962, Nagy et al. announced the discovery of 'organised elements' embedded in the Orgueil meteorite that were purportedly biological structures of extraterrestrial origin. These elements were subsequently shown to be either pollen (including that of ragwort) and fungal spores (Fitch & Anders, 1963) that had contaminated the sample, or crystals of the mineral olivine.