Part 4

Meteorites
! Largely, meteorites are residue from Solar System formation and condensation
! Comprise a wide range of compositions, which formed at various epochs in our
system’s s early history
! Chondrites
• Most common type of meteorite, date to 4.5 Ga
• Undifferentiated, congealed directly by condensation from solar nebula
• Relative concentrations of elements is close to solar (sans H, He)
! Achondrites
! Irons
• Partially differentiated meteorites
• May derive from planetoids that underwent partial chemical differentiation
• Differ in mineral composition
• Thought to derive from earliest phases of solar nebula condensation, or from cores of
differentiated planetoids that were subsequently shattered by impact
! Carbonaceous Chondrites
• Most primitive meteorites, fairly rare
• Contain abundant organic carbon, amino acids, hydrocarbons… retained from condensation
in early solar system evolution in outer system