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In the widely accepted giant impact hypothesis, the Earth-Moon system
originates from a collision between two planetary-sized bodies toward the
end of Earth accretion. Following such a collision, a circumplanetary disk
of molten and vaporized material surrounds the Earth from which the Moon
rapidly forms. Our understanding of what happens during this fluid stage of
the evolution is poor. The goal of my work here is to forge a connection
between the formation process and the lunar composition as observed in the
isotopes and chemistry of lunar samples.|
Over the course of the past two decades, isotope geochemists have observed an increasingly precise match in isotopic abundances of oxygen , titanium , silicon , and tungsten  between rocks derived from Earth's mantle and Moon against a background isotopic heterogeneity among sampled Solar System bodies. The similarity is such as to leave little doubt that these two bodies are derived from the same reservoir. But if the Moon is the result of a collision between two distinct planetary bodies, where is the isotopic evidence for the impacting planet? The scenario that I developed with Dave Stevenson is that Earth's magma ocean and the proto-lunar magma disk underwent an episode of isotopic equilibration through exchange with a common vapor atmosphere in the energetic aftermath of the giant impact while the system existed in a fluid state .
Silicate Earth-Moon differences|
If turbulent mixing - or any other process - was responsible for deriving the lunar material from Earth's mantle, what is the origin of the chemical differences between these two reservoirs? My work has focused on understanding the FeO enrichment of the lunar mantle , the presence of water in the lunar interior [7, 8], and the development of new isotopic tracers for lunar origin from a circumterrestrial disk . A major new development is the measurement of isotopic differences between the silicate Earth and Moon [e.g., 10] and this is a topic of current study.