Effect of Reimpacting Debris on the Solidification of the Lunar Magma Ocean

Viranga Perera, Alan P. Jackson, Linda Elkins-Tanton, Erik Asphaug

Research output: Contribution to journalArticle

2 Scopus citations

Abstract

Anorthosites that comprise the bulk of the lunar crust are believed to have formed during solidification of a lunar magma ocean (LMO) in which these rocks would have floated to the surface. This early flotation crust would have formed a thermal blanket over the remaining LMO, prolonging solidification. Geochronology of lunar anorthosites indicates a long timescale of LMO cooling, or remelting and recrystallization in one or more late events. To better interpret this geochronology, we model LMO solidification in a scenario where the Moon is being continuously bombarded by returning projectiles released from the Moon-forming giant impact. More than one lunar mass of material escaped the Earth-Moon system onto heliocentric orbits following the giant impact, much of it to come back on returning orbits for a period of 100 Myr. If large enough, these projectiles would have punctured holes in the nascent floatation crust of the Moon, exposing the LMO to space and causing more rapid cooling. We model these scenarios using a thermal evolution model of the Moon that allows for production (by cratering) and evolution (solidification and infill) of holes in the flotation crust that insulates the LMO. For effective hole production, solidification of the magma ocean can be significantly expedited, decreasing the cooling time by more than a factor of 5. If hole production is inefficient, but shock conversion of projectile kinetic energy to thermal energy is efficient, then LMO solidification can be somewhat prolonged, lengthening the cooling time by 50% or more.

Original languageEnglish (US)
Pages (from-to)1168-1191
Number of pages24
JournalJournal of Geophysical Research: Planets
Volume123
Issue number5
DOIs
StatePublished - May 2018

Keywords

  • Moon
  • debris
  • lunar crust
  • lunar geochronology
  • lunar magma ocean
  • reimpacts

ASJC Scopus subject areas

  • 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

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