Two-source terrestrial planet formation with a sweeping secular resonance

TL;DR

This paper presents a new model for terrestrial planet formation involving a sweeping secular resonance that explains the chemical and orbital structure of the inner Solar System through N-body simulations.

Contribution

It introduces a two-reservoir model with a sweeping secular resonance that links orbital dynamics to chemical gradients, unifying planet formation and asteroid belt composition.

Findings

The model reproduces the orbital architecture of terrestrial planets.

It explains the chemical oxidation gradients from Mercury to Mars.

It accounts for the origin of asteroid parent bodies and meteorite types.

Abstract

The models that most successfully reproduce the orbital architecture of the Solar System terrestrial planets start from a narrow annulus of material that grows into embryos and then planets. However, it is not clear how this ring model can be made consistent with the chemical structure of the inner Solar System, which shows a reduced-to-oxidized gradient from Mercury to Mars and a parallel gradient in the asteroid belt. We propose that there were two primary reservoirs in the early inner Solar System: a narrow, refractory enriched ring inside of 1 au, and a less massive, extended planetesimal disk outside of 1 au with oxidation states ranging from enstatite chondrites to ordinary chondrites. We show through a suite of N-body simulations that an inwardly sweeping secular resonance, caused by aerodynamic drag and perturbations from a mean-motion resonant Jupiter and Saturn, gathers the outer planetesimal disk into a narrow ring that migrates radially, forms Mars, and contributes oxidized material to proto-Earth. Remaining unaccreted planetesimals can be implanted into the asteroid belt as the parent bodies of aubrites and non-carbonaceous iron meteorites, while the most reduced material is not implanted and thus unsampled in the meteorite collection. This model explains the oxidation and isotopic gradients within the inner Solar System within the context of a low-viscosity, magnetic wind-driven disk.