Sulfides in Mercury's Mantle: Implications for Mercury's Interior as Interpreted From Moment of Inertia

Abstract

AbstractThe partitioning of sulfur between Mercury's core and mantle reflects its formation conditions and early evolution. If Mercury's core and mantle equilibrated under reducing conditions, and if Mercury is not depleted in sulfur relative to chondrites, Mercury's mantle should contain large quantities (7–11 wt.%) of sulfur in the form of Ca or Mg‐rich sulfides. Using petrologic constraints, we estimate the quantity of these sulfides and the implications of a sulfide‐rich mantle for Mercury's radial density structure. We find that based on recent measurements of Mercury's outer shell moment of inertia (MoI), a sulfide‐rich, iron‐poor mantle mineralogy is consistent with a low value of Mercury's polar MoI (0.333 MR2). Alternatively, a higher value for Mercury's MoI (0.343 MR2) would require a sulfide‐poor mantle, indicating bulk sulfur depletion or more oxidizing conditions than implied by surface composition.