Granite-like samples of Vesta COSMOCHEMISTRY iLLUSTRATED 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

Granite-like samples of Vesta COSMOCHEMISTRY iLLUSTRATED 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 SiO 2 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 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