Howardite

Howardite is a type of stony meteorite that belongs to the HED (howardite–eucrite–diogenite) group. It is a polymict breccia, meaning it consists of a mixture of different rock fragments, predominantly eucrite-like and diogenite-like material, embedded in a fine-grained matrix.

Formation and origin: Howardites are believed to originate from the surface or near-surface regolith of asteroid 4 Vesta. They formed through impact processes that shattered and mixed eucrite crustal fragments with diogenite mantle material, followed by further impacts that reworked the debris into brecciated rocks. This sandblasted, mixed history distinguishes howardites from the more homogenous eucrites and diogenites.

Mineralogy and textures: The clasts in howardites are typically composed of pyroxene- and plagioclase-rich lithologies, reflecting eucritic and diogenitic affinities. The matrix is fine-grained and may contain glassy material or fragmented mineral grains. The overall texture is irregular and brecciated, with a range of clast sizes.

Classification and significance: Howardites are one of the principal components of the HED meteorite suite, together with eucrites and diogenites, and are commonly interpreted as regolith-derived rocks from Vesta. Their study provides insights into Vesta’s crustal differentiation, surface processes, and the history of bombardment in the early Solar System.

Occurrence: Howardites have been found in meteorite collections worldwide and are used to infer the geological history of Vesta and similar differentiated bodies.