Late Accretion of Ceres-like Asteroids and Their Implantation into the Outer Main Belt

TL;DR

This study analyzes low-albedo asteroids in the outer main belt, revealing they share compositions with Ceres, likely originated from distant regions, and were implanted during giant planet instability, shedding light on solar system formation.

Contribution

It provides spectral and thermal models showing Ceres-like asteroids' composition, origin, and late accretion history, highlighting their implantation during planetary dynamical instability.

Findings

Ceres-like asteroids share spectral features with Ceres.

These asteroids accreted 1.5-3.5 Myr after CAIs formation.

They were likely implanted from distant regions during giant planet instability.

Abstract

Low-albedo asteroids preserve a record of the primordial solar system planetesimals and the conditions in which the solar nebula was active. However, the origin and evolution of these asteroids are not well-constrained. Here we measured visible and near-infrared (0.5 - 4.0 microns) spectra of low-albedo asteroids in the mid-outer main belt. We show that numerous large (d > 100 km) and dark (geometric albedo < 0.09) asteroids exterior to the dwarf planet Ceres' orbit share the same spectral features, and presumably compositions, as Ceres. We also developed a thermal evolution model that demonstrates that these Ceres-like asteroids have highly-porous interiors, accreted relatively late at 1.5 - 3.5 Myr after the formation of calcium-aluminum-rich inclusions, and experienced maximum interior temperatures of < 900 K. Ceres-like asteroids are localized in a confined heliocentric region between 3.0 - 3.4 au but were likely implanted from more distant regions of the solar system during the giant planet's dynamical instability.