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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 observed lunar composition (in terms of
isotopes and chemistry).|
I. Earth-Moon isotopic homogeneity
Over the course of the past decade, isotope geochemists have observed an increasingly precise match in isotopic abundances of oxygen , titanium , silicon , and tungsten  between rocks derived from the Earth's mantle and Moon against a background isotopic heterogeneity among 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? What happened to the isotopically exotic, non-terrestrial material? One possibility 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 .
II. Earth-Moon chemical differences|
If turbulent mixing is responsible for the isotopic similarities between Earth mantle and Moon, what is the origin of the chemical differences between these two silicate reservoirs? The clearest and most unambiguous of these differences is the relative dearth of volatile trace elements observed in the Apollo samples. Such elemental abundances were almost certainly established by liquid-vapor partitioning . I am currently developing coupled physical-chemical models of the evolution of the proto-lunar disk with the goal of forging a connection between the processes accompanying lunar origin and the remnant observables.
III. Origin of Lunar Hydrogen|
|After decades of scientific thought maintaining that the Moon was essentially devoid of water, recent work has revealed the presence of indigenous hydrogen in the lunar material . Such a discovery of indigenous lunar hydrogen raises questions about its origin: are we measuring a remnant of primordial lunar hydrogen inherited at birth or implantation of hydrogen via impacts  by water-rich impactors? Collaborators and I have investigated the behavior of hydrogen in the proto-lunar disk and have developed a new mechanism for the origin of the recently observed lunar water .|