The Complicated Geologic History
of Asteroid 4 Vesta
• Spectral studies of the HED
meteorites show that they
likely come from asteroid 4
Vesta.
• HED stands for:
- Howardites, which are mixtures of:
- Eucrites (basaltic lava flows)
- Diogenites (orthopyroxenites)
• The howardites contain rock
and mineral fragments, and
impact-produced glasses
• The glass fragments and
spherules record the
compositions of a wide range
of lithologies on Vesta
PSRDpresents
http://www.psrd.hawaii.edu/June09/Vesta.granite-like.html
The Complicated Geologic History
of Asteroid 4 Vesta
• Rock samples of
eucrites plot in the
basalt field on this
widely-used diagram to
classify igneous rocks.
• Most glasses are
similar to the rocks, but
are enriched in alkalis
• A few glasses are
enriched in SiO2 and
alkalis, falling into the
dacite field (≈ granite)
• This indicates that
extensive fractional
crystallization of
magmas occurred on
Vesta
PSRDpresents
http://www.psrd.hawaii.edu/June09/Vesta.granite-like.html
The Complicated Geologic History
of Asteroid 4 Vesta
An interesting picture of Vesta:
• Metamorphism
• Intrusions into the crust:
magmatic differentiation,
contact metamorphism
• Partial melting of the crust in
some places
• Magma mixing between
crustal partial melts and
eucrite basalt magma
• Eucrite basalt magma
migration through crust
• Granites could form in
intrusions or in the residual
magma ocean
PSRDpresents
http://www.psrd.hawaii.edu/June09/Vesta.granite-like.html