Earth and Terrestrial Planet Formation

TL;DR

This paper reviews the stages of Earth and terrestrial planet formation, emphasizing pebble accretion, critiques classical models, and highlights the success of the Grand Tack model in explaining the Solar System's structure.

Contribution

It introduces the pebble growth process in planet formation and evaluates various models, demonstrating the effectiveness of the Grand Tack scenario in reproducing Solar System features.

Findings

Grand Tack model successfully explains Earth's small mass and orbital structure.

Growth of Earth aligns with Weibull distribution.

Feeding zones of planets are influenced by Jupiter's position.

Abstract

The growth and composition of Earth is a direct consequence of planet formation throughout the Solar System. We discuss the known history of the Solar System, the proposed stages of growth and how the early stages of planet formation may be dominated by pebble growth processes. Pebbles are small bodies whose strong interactions with the nebula gas lead to remarkable new accretion mechanisms for the formation of planetesimals and the growth of planetary embryos. Many of the popular models for the later stages of planet formation are presented. The classical models with the giant planets on fixed orbits are not consistent with the known history of the Solar System, fail to create a high Earth/Mars mass ratio, and, in many cases, are also internally inconsistent. The successful Grand Tack model creates a small Mars, a wet Earth, a realistic asteroid belt and the mass-orbit structure of the terrestrial planets. In the Grand Tack scenario, growth curves for Earth most closely match a Weibull model. The feeding zones, which determine the compositions of Earth and Venus follow a particular pattern determined by Jupiter, while the feeding zones of Mars and Theia, the last giant impactor on Earth, appear to randomly sample the terrestrial disk. The late accreted mass samples the disk nearly evenly.