HED meteorites
 a eucrite
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HEDs
Howardite-Eucrite-Diogenite (HED) meteorites are basaltic rocks and are thought to be derived from the
asteroid Vesta.
Asteroid Vesta is the second biggest asteroid of diameter ~ 500 km, in the asteroid belt and
is the only largely preserved proto-planet left in the solar system which was
differentiated into a layered structure of a core, mantle and crust. Despite its small size,
Vesta mirrored the behaviour of rocky planets shortly after their formation without subsequent
tectonic or volcanic modifications. Therefore, understanding the volatiles in Vesta can give
powerful constraints on the evolution of differentiated bodies and their abundances shorty
after the differentiation.
Isotopic and elemental ratios of noble gases in HED's provides the clue to the degassing history,
and their inventory after the differentiation of Vesta. Eucrites and diogenites are representative
of the interior parts of Vesta. On the other hand, howardites are composed of fragments from
eucrites, diogenites and impactors. Howardites are regolithic origin and gives clues to
the surface activities on Vesta.
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