Granite-like samples of Vesta COSMOCHEMISTRY iLLUSTRATED

The Complicated Geologic History The Complicated Geologic History

of Asteroid 4 Vestaof 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

Granite-like samples of Vesta COSMOCHEMISTRY iLLUSTRATED

The Complicated Geologic History The Complicated Geologic History

of Asteroid 4 Vestaof 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

Granite-like samples of Vesta COSMOCHEMISTRY iLLUSTRATED

The Complicated Geologic History The Complicated Geologic History

of Asteroid 4 Vestaof Asteroid 4 VestaAn 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