A wet, heterogeneous lunar interior: Lower mantle and core dynamo evolution

A. J. Evans, M. T. Zuber, B. P. Weiss, S. M. Tikoo

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

While recent analyses of lunar samples indicate the Moon had a core dynamo from at least 4.2-3.56 Ga, mantle convection models of the Moon yield inadequate heat flux at the core-mantle boundary to sustain thermal core convection for such a long time. Past investigations of lunar dynamos have focused on a generally homogeneous, relatively dry Moon, while an initial compositionally stratified mantle is the expected consequence of a postaccretionary lunar magma ocean. Furthermore, recent re-examination of Apollo samples and geophysical data suggests that the Moon contains at least some regions with high water content. Using a finite element model, we investigate the possible consequences of a heterogeneously wet, compositionally stratified interior for the evolution of the Moon. We find that a postoverturn model of mantle cumulates could result in a core heat flux sufficiently high to sustain a dynamo through 2.5 Ga and a maximum surface, dipolar magnetic field strength of less than 1 μT for a 350-km core and near -2 μT for a 450-km core. We find that if water was transported or retained preferentially in the deep interior, it would have played a significant role in transporting heat out of the deep interior and reducing the lower mantle temperature. Thus, water, if enriched in the lower mantle, could have influenced core dynamo timing by over 1.0 Gyr and enhanced the vigor of a lunar core dynamo. Our results demonstrate the plausibility of a convective lunar core dynamo even beyond the period currently indicated by the Apollo samples. Key Points A heterogeneous and wet mantle could have increased core dynamo by up to 2.0 Gyr Enriched water could have influenced core dynamo timing by up to 1.0 Gyr Plausibility of convective lunar dynamo beyond period indicated by lunar samples

Original languageEnglish (US)
Pages (from-to)1061-1077
Number of pages17
JournalJournal of Geophysical Research E: Planets
Volume119
Issue number5
DOIs
StatePublished - May 2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Keywords

  • KREEP
  • Moon
  • convection
  • core dynamo
  • heat flux
  • water

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