An Oxygen Isotope Mixing Model for the Accretion and Composition of Rocky Planets |
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Authors: | Katharina Lodders |
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Institution: | (1) Planetary Chemistry Laboratory, Department of Earth and Planetary Sciences, Washington University, St. Louis, MO 63130-4899, USA |
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Abstract: | The oxygen isotope systematics in planetary and nebular matter are used to constrain the types of nebular material accreted
to form a planet. The basic assumption of this model is that the mean oxygen isotopic composition of a planet is determined
by the weighted mean oxygen isotopic composition of nebular matter accreted by the planet. Chondrites are taken as representatives
of nebular matter. The chemical composition (which determines core size, mantle oxidation state, density, moment of inertia)
of a planet results from the weighted mean compositions of the accreted nebular material, once the mass fractions of the different
types of accreting matter are known. Here some results for Earth, Moon, Mars, and Vesta are discussed. The model implies that
loss of volatile elements, such as alkalis and halogens, occurs during accretion and early planetary differentiation (e. g., by catastrophic impacts). The possible depletion mechanisms of moderately volatile elements are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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