Mantle composition. 1800s meteorites contain similar minerals to terrestrial rocks Hypothesis that meteorites come from asteroid belt and originate from a single planet with metallic core a silicate mantle and crust Earth must be similar. Mantle composition.
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Where does it all come from?
Drake and Righter, Nature, 2002
Intense processing and geochemical variety of terrestrial samples accessible to observations together with the existence of inaccessible domains in the deep Earth, do not allow us to built a verifiable picture of the mean composition of the Earth.
What is the primitive composition from which all known rocks must evolve.
Chondrites are meteorites that have changed little since they first formed 4.5 billion year ago. They have a primitive (close to solar minus volatiles) composition.
The composition of the Earth's primitive upper mantle (PUM, the Earth's mantle immediately after core formation) is distinct from that of any kind of primitive meteorite.
Geochemical processes on differentiated planets tend to raise the Mg/Si ratio and lower the Al/Si ratio in mantle materials from which magma has been extracted, reflecting the compatible nature of Mg and the incompatible nature of Al. Thus, Mg/Si and Al/Si ratios in samples from both Earth and Mars correlate with a negative slope. In contrast, primitive materials show a loose positive correlation of unknown meaning.
Earth same oxygen reservoir than moon and enstatite meteorites.
Different from Mars (which is close to Earth)
Distinct oxygen reservoirs over small distances in solar nebula
PUM overlaps with anhydrous ordinary chondrites
Explains late veneer: addition of chondritic material after core formation
Earth similar to carbonaceous chondrites
Different from Mars
Local reservoirs in solar nebula
Palme and O’Neill 2003