The moon and the planets

, Volume 18, Issue 4, pp 465–478 | Cite as

The moon: Composition determined by nebular processes

  • John W. Morgan
  • Jan Hertogen
  • Edward Anders
Article

Abstract

The bulk composition of the Moon was determined by the conditions in the solar nebula during its formation, and may be quantitatively estimated from the premise that the terrestrial planets were formed by cosmochemical processes similar to those recorded in the chondrites. The calculations are based on the Ganapathy-Anders 7-component model using trace element indicators, but incorportate improved geophysical data and petrological constraints.

A model Moon with 40 ppb U, a core 2% by weight (1.8% metal with ∼35% Ni and 0.2% FeS) and Mg/(Fe2++Mg)Δ∼0.75 meets the trace element restrictions, and has acceptable density, heat flow and moment of inertia ratio. The high Ni content of the core permits low-Ti mare basalts to equilibrate with metal, yet still retain substantial Ni. The silicate resembles the Taylor-Jakeš composition (and in some respects the waif Ganapathy-Anders Model 2a), but has lower SiO2.

Minor modifications of the model composition (U=30–35 ppb) yield a 50% melt approximating Apollo 15 green glass and a residuum of olivine plus 3 to 4% spinel; the low SiO2, favors spinel formation, and, contrary to expectation, Cr is not depleted in the liquid. There may no longer be any inconsistency between the cosmochemical approach and arguments based on experimental petrology.

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Copyright information

© D. Reidel Publishing Company 1978

Authors and Affiliations

  • John W. Morgan
    • 1
  • Jan Hertogen
    • 2
  • Edward Anders
    • 2
  1. 1.National CenterU.S. Geological SurveyRestonUSA
  2. 2.Enrico Fermi Institute and Department of ChemistryUniversity of ChicagoUSA
  3. 3.Instituut voor Nucleaire WetenschappenRijksuniversiteit GentGentBelgium

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