Crystals stirred not shaken

Figure: Map of the lunar surface
Source: NASA

The lunar crust is thought to have formed through flotation of buoyant plagioclase crystals which are apparent even from Earth due to their white color) at a time when the rocky mantle of the Moon was still largely molten. However, it remains contentious whether plagioclase would have been able to float in a turbulently convecting magma ocean. In this project, we test under which fluid dynamical conditions the mineral phases that crystallize during the various stages of magma ocean solidification on the Moon are able to settle and float. For this purpose, we have developed and benchmarked a computational methodology with which we can investigate solid-fluid coupling in a lunar magma ocean from first principles without relying on aprior assumptions about settling speed or drag. Our simulations indicate that plagioclase flotation is hindered primarily by the simultaneous crystallization of heavy mineral phases, but would nonetheless be possible if the crystal fraction in suspension remained low (<10%).
Collaborators: Lindy Elkins-Tanton, James Sethian, Jiun-der Yu