eucrite

Eucrite is a class of achondritic meteorites that represents basaltic rocks originating from asteroid 4 Vesta. Along with diogenites and howardites, eucrites form part of the HED meteorite group, a collective name for basaltic to pyroxene-rich rocks linked to Vesta by composition and orbital history.

Mineralogy and texture commonly define eucrites. They are dominated by calcic plagioclase feldspar and calcium-rich pyroxene, typically ranging from pigeonite to augite. Olivine is rare or absent in most eucrites, and accessory minerals may include chromite and iron oxides. Textures vary from fine-grained, subophitic to ophitic, reflecting rapid cooling during crustal crustal formation or brecciation.

Classification within eucrites includes monomict eucrites, which are nearly homogeneous, and polymict eucrites, which are breccias containing multiple lithologies. Polymict eucrites form through impact mixing on Vesta’s surface and can include clasts of diogenites or other basaltic materials. Howardites, a related group, are regolith breccias composed of eucrite and diogenite fragments in a common matrix.

Origin and age are tied to Vesta’s early crustal differentiation. Eucrites crystallized from basaltic magmas produced by partial melting and differentiation in the early Solar System, with formation typically placed in the first few hundred million years after solar system formation, around 4.5 billion years ago. Subsequent impacts produced breccias and regolith deposits that preserve a record of Vesta’s geologic history. The Dawn spacecraft’s observations of Vesta corroborate the link between eucrites and basaltic crust on the asteroid.