The Case Against an Early Lunar Dynamo Powered by Core Convection

Alexander J. Evans, Sonia M. Tikoo, Jeffrey C. Andrews-Hanna

Research output: Contribution to journalArticlepeer-review

18 Scopus citations

Abstract

Paleomagnetic analyses of lunar samples indicate that the Moon had a dynamo-generated magnetic field with ~50 μT surface field intensities between 3.85 and 3.56 Ga followed by a period of much lower (≤ ~5 μT) intensities that persisted beyond 2.5 Ga. However, we determine herein that there is insufficient energy associated with core convection—the process commonly recognized to generate long-lived magnetic fields in planetary bodies—to sustain a lunar dynamo for the duration and intensities indicated. We find that a lunar surface field of ≤1.9 μT could have persisted until 200 Ma, but the ~50 μT paleointensities recorded by lunar samples between 3.85 and 3.56 Ga could not have been sustained by a convective dynamo for more than 28 Myr. Thus, for a continuously operating, convective dynamo to be consistent with the early lunar paleomagnetic record, either an exotic mechanism or unknown energy source must be primarily responsible for the ancient lunar magnetic field.

Original languageEnglish (US)
Pages (from-to)98-107
Number of pages10
JournalGeophysical Research Letters
Volume45
Issue number1
DOIs
StatePublished - Jan 16 2018

Keywords

  • Moon
  • convection
  • core
  • dynamo
  • lunar
  • magnetic

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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