Different arrival times of CM and CI-like bodies from the outer Solar System to the asteroid belt

TL;DR

This study uses N-body simulations to trace the origins and implantation times of CM and CI-like bodies in the asteroid belt, revealing their different formation regions and migration histories related to giant planet growth.

Contribution

It provides a novel dynamical model linking the formation regions and migration timing of primitive bodies to giant planet evolution and gas disk profiles.

Findings

CM bodies originate from Saturn's formation region.

CI bodies originate from the trans-Uranian disk.

CM-like bodies contributed to Earth's water budget.

Abstract

Understanding the provenance of CI and CM chondrites, the most primitive materials in our meteorite collections, is critical for shedding light on the Solar System's early evolution and contextualizing findings from recent sample return missions. Here we show that the parent bodies of CM chondrites originate from the Saturn formation region, whereas those of CI chondrites originate essentially from the primordial trans-Uranian disk. Using Nbody simulations to investigate the effect of giant planet growth and inward Type-I migration, along with the current observed distribution of CM, CI, and comet-like P types bodies in the asteroid belt, we demonstrate that CI- and CM-like bodies must have been implanted at different times in the belt. In contrast, CI and comet-like bodies were implanted at the same time. These different implantation periods are imposed by the fact that the gas disk profile entirely governs the radial distribution of bodies implanted by aerodynamic drag in the asteroid belt. A preferred location coincides with the inner edge of a gap opened by Jupiter. Saturn's growth likely drove the migration of CM-like bodies. In contrast, CI and comet-like bodies were transported at a later stage during the outward migration of Uranus and Neptune, driven by remaining planetesimals. Since CM chondrites are chondrule-rich, it follows that chondrule formation occurred mostly inward of the ice giants formation zone (under 10 au). A byproduct of our simulations is that only CM-like, not CI-like, bodies contributed to the water budget of the telluric planets.