The terrestrial planet formation paradox inferred from high-resolution N-body simulations

TL;DR

This study uses high-resolution N-body simulations to explore how different initial orbital assumptions for Jupiter and Saturn affect terrestrial planet formation, revealing a paradox between dynamical models and cosmochemical evidence.

Contribution

It demonstrates the impact of initial giant planet orbits on terrestrial planet formation and highlights a paradox between dynamical simulations and cosmochemical data.

Findings

EJS scenario matches current inner solar system architecture.

CJS scenario reproduces low radial mixing but not the current architecture.

A paradox exists between dynamical models and isotopic evidence.

Abstract

Recent improvements to GPU hardware and the symplectic N-body code GENGA allow for unprecedented resolution in simulations of planet formation. In this paper, we report results from high-resolution N-body simulations of terrestrial planet formation that are mostly direct continuation of our previous 10 Myr simulations (Woo et al. 2021a) until 150 Myr. By assuming that Jupiter and Saturn have always maintained their current eccentric orbits (EJS), we are able to achieve a reasonably good match to the current inner solar system architecture. However, due to the strong radial mixing that occurs in the EJS scenario, it has difficulties in explaining the known isotopic differences between bodies in the inner solar system, most notably between Earth and Mars. On the other hand, assuming initially circular orbits for Jupiter and Saturn (CJS) can reproduce the observed low degree of radial mixing in the inner solar system, while failing to reproduce the current architecture of the inner solar system. These outcomes suggest a possible paradox between dynamical structure and cosmochemical data for the terrestrial planets within the classical formation scenario.