Evidence for lunar true polar wander and a past low-eccentricity, synchronous lunar orbit

James Tuttle Keane, Isamu Matsuyama

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

As first noted 200 years ago by Laplace, the Moon's rotational and tidal bulges are significantly larger than expected, given the Moon's present orbital and rotational state. This excess deformation has been ascribed to a fossil figure, frozen in when the Moon was closer to the Earth. However, the observed figure is only consistent with an eccentric and non-synchronous orbit, contrary to our understanding of the Moon's formation and evolution. Here, we show that lunar mascons and impact basins have a significant contribution to the observed lunar figure. Removing their contribution reveals a misaligned fossil figure consistent with an early epoch of true polar wander (driven by the formation of the South Pole-Aitken Basin) and an early low-eccentricity, synchronous lunar orbit. This new self-consistent model solves a long-standing problem in planetary science and will inform future studies of the Moon's dynamical evolution and early dynamo. Key Points Lunar impact basins have a significant contribution to the lunar inertia tensorThe formation of the South Pole-Aitken basin reoriented the Moon ~15°The Moon's lithosphere formed in a smaller, synchronous, low-eccentricity orbit

Original languageEnglish (US)
Pages (from-to)6610-6619
Number of pages10
JournalGeophysical Research Letters
Volume41
Issue number19
DOIs
StatePublished - Oct 16 2014

Keywords

  • GRAIL
  • South Pole-Aitken
  • lunar figure
  • lunar orbit
  • true polar wander

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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