Allendechondriet

Allendechondriet, commonly referred to as the Allende meteorite, is a CV3 carbonaceous chondrite that fell in 1969 near the town of Allende in Chihuahua, Mexico. It is one of the most extensively studied meteorites and among the oldest materials available for laboratory study of the early solar system.

Classification and composition: Allende is classified as a CV3 carbonaceous chondrite. It preserves a primitive assemblage of chondrules embedded in fine-grained matrix and is rich in calcium-aluminum-rich inclusions (CAIs), which are among the oldest known solids in the solar system. The meteorite shows limited aqueous alteration and low degrees of thermal metamorphism, preserving primordial features that record conditions in the early solar nebula.

Significance: CAIs in Allende, dated at about 4.567 billion years old, provide key constraints on the timing of solar system formation. Oxygen and other isotopic analyses reveal nucleosynthetic heterogeneities in the solar nebula. As a result, Allende has been central to models of early solar system processes, including condensation, melting, and mixing in the protoplanetary disk.

Fall and distribution: The fall occurred on February 8, 1969, and thousands of fragments were recovered and subsequently distributed to institutions worldwide. The meteorite is widely represented in museum collections and continues to be a reference material in cosmochemistry.