A Numerical Approach Using a Finite Element Model to Constrain the Possible Interior Layout of (16) Psyche

Abstract

Asteroid (16) Psyche (278 × 238 × 171 km in size) is notable for the largest M-type asteroid and has the high radar albedo (0.34 ± 0.08) among the main-belt asteroids. The object is likely a mixture of metal and silicates because of its lower bulk density (∼4.0 g cm−3) than metallic materials (∼7.5 g cm−3) and observations inferring the existence of silicate materials on the surface. Here, we numerically investigate the interior layout when the structure of Psyche consists of a spherical iron core and two types of the silicate-rich layers (compressed and uncompressed ones) resulting from the compaction process (later known as a three-layer model). We develop an inverse problem algorithm to determine the layout distribution by combining a finite element model approach that accounts for density variations and constrains pressure-based crushing conditions. The results show that, given the crushing limit of 10 MPa, the smallest core size likely reaches 72 km in radius, and the silicate-rich layer, consisting of both compressed and uncompressed regions, has a thickness ranging up to 68 km. To support the localized metal concentration at the crater-like region detected in the recent radar observation, we give more constraints on the minimum core size, which takes up to 34%–40% of the entire size of Psyche. Our study also addresses that the ferrovolcanic surface eruptions could still be a source of metal-rich materials. Finally, while the differentiated structure having a spherical core condition is just part of potential scenarios, the present study infers that the core and compressed layer conditions likely control the surface condition. Further investigations will provide key information for observable properties on NASA’s Psyche mission to provide insight into its evolution history.

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