Schematic example illustration for the knowledge article “Achondrites”
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Detailed explanation

Achondrites have igneous or strongly reworked textures. They come from bodies where original material was at least partly melted and separated.

They include asteroidal groups such as HED, aubrites, angrites and ureilites, as well as lunar and Martian meteorites.

Defining feature
no chondrules

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Groups and subgroups

These cards show the next classification level. Linked groups open their own detailed explanation.

HED meteorites

Howardites, eucrites and diogenites; a major, well-supported family linked to asteroid Vesta.

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Aubrites

Enstatite-rich achondrites formed under extremely oxygen-poor conditions.

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Angrites

Very old basaltic to plutonic achondrites with distinctive mineralogy and isotope signatures.

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Ureilites

Carbon-bearing, commonly olivine- and pyroxene-rich achondrites with a complex, incomplete differentiation history.

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Acapulcoites–lodranites

Primitive achondrites recording a transition from intense metamorphism to partial melting.

Brachinites

Olivine-rich achondrites whose exact origins within differentiated parent bodies remain under study.

Winonaites

Primitive achondrites chemically related to the IAB iron-meteorite complex.

Lunar meteorites

Impact-ejected lunar material identified by mineralogical, chemical and isotopic evidence.

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Martian meteorites

Rocks from Mars including shergottites, nakhlites, chassignites and rare additional types.

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Resemblance to terrestrial rocks

Because both can form through geological melting and crystallisation, many achondrites resemble terrestrial basalts or plutonic rocks. Secure identification requires laboratory data.

Differentiation: from starting material to planetary rock

When a small planetary body is heated strongly enough, part of it melts. Dense metal may sink inward while silicate melts form mantle and crust. Achondrites are products or remnants of such processes.

Their textures may be basaltic, plutonic, brecciated or strongly recrystallised. The absence of chondrules is important but does not by itself identify a group.

Asteroidal and planetary achondrites

HED meteorites, angrites, aubrites and ureilites represent different asteroidal parent bodies. Lunar and Martian meteorites are planetary achondrites whose origins are supported by several independent laboratory indicators.

Primitive achondrites record only partial melting and preserve more original features. The boundary between primitive and fully differentiated describes a process, not a simple visual category.

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Editorially paraphrased and expanded from the linked specialist and primary sources; reviewed 24 August 2026. New classifications and database entries may require later updates.