Velocity-density systematics, mean atomic weight, and the interior of the moon

Abstract Mean atomic weight profiles for the lunar mantle have been calculated from velocity-density systematic relations using lunar density and seismic velocity models. Despite large variability among the models, the calculation including Poisson's ratio yields a range of mean atomic weight values between 22 and 23 g mol −1 below 150 km. A similar calculation for the Earth's mantle produces a mean atomic weight of 21.1 ±0.4 g mol −1 . This suggests that the Moon cannot be derived directly from the Earth's mantle, or that it has had a differentiation history different from the Earth's. The lunar m ' s require an Fe mole fraction between 0.25 and 0.33 for a pure olivine mantle, or between 0.33 and 0.45 for pure pyroxene. The present profiles are 0.5–3.0 g mol −1 higher than those calculated from lunar compositional models based on lunar rock compositions and petrology and assumed lunar histories, indicating inadequacies in either the seismic or compositional models, or in both. The mean atomic weight approach provides a method of comparing the consistency of seismic and compositional models of planetary interiors.

[1]  Lunar sample Preliminary Examination Team.  Preliminary examination of lunar samples from apollo 12. , 1971, Science.

[2]  Nai-hsien Mao,et al.  Uniformity of Mantle Composition , 1975 .

[3]  Apollo Preliminary Examination Team.  The apollo 16 lunar samples: petrographic and chemical description. , 1973, Science.

[4]  N. Mao,et al.  Velocity-density systematics and its implications for the iron content of the mantle , 1974 .

[5]  T. Jordan,et al.  Earth structure from free oscillations and travel times: Geophys , 1974 .

[6]  D. L. Anderson.  On the composition of the lunar interior , 1975 .

[7]  N. Fujii,et al.  Elastic wave velocities and thermal diffusivities of Apollo 14 rocks , 1972 .

[8]  Apollo Preliminary Examination Team.  Apollo 17 lunar samples: chemical and petrographic description. , 1973, Science.

[9]  Apollo Preliminary Examination Team.  The apollo 15 lunar samples: a preliminary description. , 1972, Science.

[10]  Herbert F. Wang.  Elastic constant systematics , 1978 .

[11]  J. Watt,et al.  Mixed-oxide and perovskite-structure model mantles from 700-1200 km , 1978 .

[12]  F. Birch,et al.  Composition of the Earth's Mantle , 1937 .

[13]  D. L. Anderson.  The composition and origin of the moon. , 1973 .

[14]  S. R. Taylor.  Geochemical constraints on melting and differentiation of the moon. , 1978 .

[15]  T. Shankland,et al.  Elastic properties, chemical composition, and crystal structure of minerals , 1977 .

[16]  Gene Simmons,et al.  Velocity of compressional waves in various minerals at pressures to 10 kilobars , 1964 .

[17]  Adam M. Dziewonski,et al.  Parametrically simple earth models consistent with geophysical data , 1975 .

[18]  N. Soga,et al.  Applications to lunar geophysical models of the velocity-density properties of lunar rocks, glasses, and artificial lunar glasses , 1972 .

[19]  Lunar sample Preliminary Examination Team.  Preliminary examination of lunar samples from Apollo 11 , 1969 .

[20]  B. Bills,et al.  A lunar density model consistent with topographic, gravitational, librational, and seismic data , 1977 .

[21]  D. L. Anderson.  Removal of a constraint on the composition of the lunar interior , 1973 .

[22]  D. Chung,et al.  General relationships among sound speeds: I. New experimental information , 1974 .

[23]  E. Essene,et al.  Petrogenesis of Apollo 11 basalts, internal constitution and origin of the moon , 1970 .

[24]  P. W. Gast.  The chemical composition and structure of the moon , 1972 .

[25]  M. N. Toksoz,et al.  Seismic investigation of the lunar interior , 1976 .

[26]  G. Latham,et al.  Seismic structure of the moon - A summary of current status , 1976 .

[27]  A. E. Ringwood,et al.  Basaltic magmatism and the bulk composition of the moon , 1977 .

[28]  T. Shankland,et al.  Velocity‐density systematics: Derivation from Debye theory and the effect of ionic size , 1972 .

[29]  M. Ewing,et al.  Deep lunar interior inferred from recent seismic data , 1974 .

[30]  S. Solomon.  Density within the moon and implications for lunar composition , 1974 .

[31]  P. W. Gast,et al.  Density of the lunar interior , 1972 .

[32]  J. Morgan,et al.  The moon: Composition determined by nebular processes , 1978 .

[33]  F. Gilbert,et al.  An application of normal mode theory to the retrieval of structural parameters and source mechanisms from seismic spectra , 1975, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.