Diogenites

Diogenites are a class of achondritic meteorites that belong to the HED (Howardite–Eucrite–Diogenite) group, a set of meteorites linked to the asteroid 4 Vesta. They are primarily orthopyroxene-rich rocks and are typically distinguished from eucrites (basaltic crust) and howardites (brecciated mixtures) by their mineralogy and texture.

Mineralogy and textures: The diogenites are dominantly orthopyroxene-dominated rocks, often classified as orthopyroxenites. They usually exhibit a coarse to fine-grained, sometimes cumulate texture, with little if any feldspar. Minor amounts of olivine and pyroxene varieties such as pigeonite can occur, and accessory minerals like chromite, troilite, and merrillite may be present.

Origin and formation: Diogenites are interpreted as representing material from the deeper parts of Vesta’s crust or mantle that crystallized from differentiated magmas. After their formation, impacts on Vesta excavated these rocks to the surface, where they were ejected and eventually delivered to Earth as meteorites. Their relationship to eucrites and howardites reflects a shared Vesta origin but different petrogenetic histories.

Age and significance: Radiometric dating places diogenites among the oldest Solar System rocks, with crystallization ages around the early 4.5-billion-year epoch. Studying diogenites provides insights into planetary differentiation, Vesta’s internal structure, and the early processes that shaped differentiated bodies in the inner Solar System.

Distribution and study: Diogenites have been identified from numerous meteorite finds worldwide. As a key component of the HED suite, they continue to inform interpretations of asteroid geology, meteorite formation, and the evolution of Vesta.