Constraints on the Feasibility of Ferrovolcanism on Asteroid 16 Psyche

Abstract

Asteroid 16 Psyche's surface appears to be highly metallic, but its bulk density suggests a silicate-rich interior. Ferrovolcanism has been suggested to explain how a silicate-rich body could develop a metallic surface. This requires trapping of light elements bearing iron-rich metallic melt in a core solidifying from the outside inwards. The buoyancy of the lighter melt must then generate sufficient pressure to carry metal melt through the mantle and cover the surface. Here, we test whether sufficient pressure could have been generated on 16 Psyche in different scenarios. Core size, light element partitioning between mantle and core, and silicate mass loss are calculated for three meteoritic bulk compositional models (H-chondrite, EH-chondrite and mesosiderite) based on mantle density and mantle porosity combinations. The resulting core compositions are used to calculate excess pressure. Mantle density and porosity combinations leading to ferrovolcanism are constrained for each bulk composition. Iron-rich bulk compositions with low light element abundances are favored. Mesosiderite bulk composition is most conducive to producing ferrovolcanism but does not naturally fit the ferrovolcanism framework. Primitive compositions are favored as the timing of ferrovolcanism is tied to the earlier stages of solar system formation. H-chondrite model scenarios may produce ferrovolcanism but require high amounts of mass loss to be considered as a building block for Psyche. EH-chondrite model scenarios are chemically not conducive to producing ferrovolcanism. Both confirmation and rejection of the ferrovolcanism hypothesis by upcoming observations from NASA's Psyche mission can therefore provide key new constraints on 16 Psyche origin and evolution scenarios.