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The Case for a Heat-Pipe Phase of Planet Evolution on the MoonThe prevalence of anorthosite in the lunar highlands is generally attributed to the flotation of less dense plagioclase in the late stages of the solidification of the lunar magma ocean. It is not clear, however, that these models are capable of producing the extremely high plagioclase contents (near 100%) observed in both Apollo samples and remote sensing data, since a mostly solid lithosphere forms (at 60-70% solidification) before plagioclase feldspar reaches saturation (at approximately 80% solidification). Formation as a floating cumulate is made even more problematic by the near uniformity of the alkali composition of the plagioclase, even as the mafic phases record significant variations in Mg/(Mg+Fe) ratios. These problems can be resolved for the Moon if the plagioclase-rich crust is produced and refined through a widespread episode of heat-pipe magmatism rather than a process dominated by density-driven plagioclase flotation. Heat-pipes are an important feature of terrestrial planets at high heat flow, as illustrated by Io's present activity. Evidence for their operation early in Earth's history suggests that all terrestrial bodies should experience an early episode of heat-pipe cooling. As the Moon likely represents the most wellpreserved example of early planetary thermal evolution in our solar system, studies of the lunar surface and of lunar materials provide useful data to test the idea of a universal model of the way terrestrial bodies transition from a magma ocean state into subsequent single-plate, rigid-lid convection or plate tectonic phases.
Document ID
20150001938
Document Type
Conference Paper
Authors
Simon, J. I. (NASA Johnson Space Center Houston, TX, United States)
Moore, W. B. (Hampton Univ. VA, United States)
Webb, A. A. G. (Louisiana State Univ. Baton Rouge, LA, United States)
Date Acquired
February 23, 2015
Publication Date
March 16, 2015
Subject Category
Lunar and Planetary Science and Exploration
Report/Patent Number
JSC-CN-32814
Meeting Information
Lunar and Planetary Science Conference(The Woodlands, TX)
Distribution Limits
Public
Copyright
Public Use Permitted.

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