Murchison

The Murchison meteorite fell on September 28, 1969, in Victoria (Australia), with a total mass of approximately 100 kg. It belongs to the CM class (Mighei-type), characterized by a high percentage of organic matter (up to 3% by weight) and a moderate degree of aqueous alteration. Its composition includes hydrated silicates, magnetite, sulfides, and a rich variety of complex organic compounds, including amino acids, polycyclic aromatic hydrocarbons (PAH), and carboxylic acids.

The internal structure displays chondrules (millimeter-sized silicate spherules) embedded in a fine matrix, evidence of aggregation processes in the protoplanetary disk. Murchison has become an extraordinary archive for studying prebiotic chemistry and the evolution of matter in the primordial cosmos. Isotopic studies have revealed anomalies in oxygen and carbon isotopes indicating extrasolar origins of some components, confirming that the meteorite contains stardust.

Classification: Carbonaceous chondrite CM2. Bulk density: 2.1 g/cm³. Primary mineralogical composition: olivine (Fa24-26, iron-rich olivine), pyroxene (enstatite and diopside), feldspar (calcic plagioclase), magnetite, troilite (FeS), native nickel-iron. Matrix: hydrated silicates (serpentine, talc, chlorite) with organic matter inclusions. Water content: 11-13% by weight. Radiometric age (Pb-Pb): 4562 ± 4 Ma. Organic composition: more than 70 identified amino acids (both L and D forms), fatty acids, nucleobases, sugars, and aliphatic and aromatic hydrocarbons. Isotopic ratio δ¹³C: -5 to +50‰ (VPDB), indicative of multiple origins. Raman spectroscopy: D and G bands of amorphous/graphitized carbon. Absence of crystalline structure in the traditional sense; the matrix is predominantly amorphous with nanometric crystallites. Mohs hardness of the silicate component: 4-5 (due to serpentine and fragile hydrated minerals).