The Complicated Geologic History of Asteroid 4 Vesta

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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

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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

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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