Mass and Density of Asteroid (16) Psyche

TL;DR

This paper introduces a new MCMC-based method to estimate asteroid masses, applied to Psyche, and finds its density suggests a non-solid iron composition, supporting ferrovolcanism hypotheses.

Contribution

The paper presents a novel MCMC algorithm for asteroid mass estimation and validates it on well-studied asteroids, providing new mass and density estimates for Psyche.

Findings

Mass of Psyche: (1.117 ± 0.039) × 10^{-11} solar masses

Bulk density of Psyche: (3.88 ± 0.25) g/cm³

Density results support ferrovolcanism hypothesis

Abstract

We apply our novel Markov-chain Monte Carlo (MCMC)-based algorithm for asteroid mass estimation to asteroid (16) Psyche, the target of NASA's eponymous Psyche mission, based on close encounters with 10 different asteroids, and obtain a mass of $(1.117 \pm 0.039) \times 10^{-11} $ solar masses. We ensure that our method works as expected by applying it to asteroids (1) Ceres and (4) Vesta, and find that the results are in agreement with the very accurate mass estimates for these bodies obtained by the Dawn mission. We then combine our mass estimate for Psyche with the most recent volume estimate to compute the corresponding bulk density as $(3.88 \pm 0.25)$ g/cm$^3$. The estimated bulk density rules out the possibility of Psyche being an exposed, solid iron core of a protoplanet, but is fully consistent with the recent hypothesis that ferrovolcanism would have occurred on Psyche.