The FeO content of the lunar mantle - insights from geophysical and petrological constraints

Abstract

The FeO/MgO ratio of the bulk silicate Moon(BSM) is poorly constrained. To address this issue,we explored the effects of changing FeO/MgO ratioson the chemical reservoirs that formed during lunarmagma ocean (LMO) crystallization and the impli-cations for the physical properties of today’s BSM. By simulating LMO crystallization we found thatLMO FeO contents control the abundance of lateformed, Fe- and Ti-rich, ilmenite-bearing cumulates(IBC). Due to their high density, IBC sink towardsthe lower mantle, where they partially melt andcause the attenuation of seismic waves observed inthe deep lunar mantle [1]. The efficiency of this IBCoverturn affects not only the thickness of the partialmelt zone but also the BSM moment of inertia(MoI). We modeled the BSM properties for differentFeO contents, overturn scenarios, core sizes and in-terior temperatures and demonstrate that the BSMFeO content can be constrained by fitting the ob-served BSM physical properties.