Moment of Inertia and Tectonic Record of Asteroid 16 Psyche May Reveal Interior Structure and Core Solidification Processes

Abstract

The thermal and chemical evolution of (16) Psyche would have been influenced by the direction of core solidification and thickness of an outer (rocky) silicate layer. We model the thermal evolution and core solidification of Psyche for a range of outer silicate layer thicknesses and core sulfur contents to calculate the resulting radial contraction and moments of inertia. We generally find that increasing the thickness of the outer silicate layer by 10 km results in a ∼1-km reduction in total radial contraction. Additionally, we find that the timing of full core solidification, and thus a large amount of predicted contraction, can differ by up to 25 Myr for inward versus outward core growth. Finally, our calculated moment-of-inertia factors for models with inward core growth that contain sulfur are consistently larger than those with outward core growth. Ultimately, spacecraft-derived estimates of Psyche's moment of inertia and surface contraction will be able to provide constraints on Psyche's interior evolution, silicate layer thickness, and direction of core solidification.