The Moon-forming Impact as a Constraint for the Inner Solar System's Formation

Abstract

The solar system planets are benchmarks for the planet formation theory. Yet two paradigms coexist for the four terrestrial planets: the prolonged collisional growth among planetesimals lasting $>100$ million years (Myr) and the fast formation via planetesimals accreting pebbles within 10 Myr. Despite their dramatic difference, we can hardly tell which theory is more relevant to the true history of the terrestrial planets' formation. Here, we show that the Moon's origin puts stringent constraints on the pebble accretion scenario, rendering it less favourable. In the pebble accretion model, the one-off giant impact between proto-Earth and Theia rarely (probability $<$ 1\textperthousand) occurs at the right timing and configuration for the Moon formation. Even if a potential impact happens by chance, giant impact simulations reveal perfect mixing between proto-Earth and Theia, leaving no room for the observed primordial Earth mantle heterogeneity and the compositional difference, though small, between Earth and the Moon. Thus, the Earth-Moon system along other terrestrial planets should preferably form from chaotic collisional growth in the inner solar system.

8 pages, 6 figures

References in corpus (30)

• GIZMO: A New Class of Accurate, Mesh-Free Hydrodynamic Simulation Methods
• REBOUND: An open-source multi-purpose N-body code for collisional dynamics
• Rapid growth of gas-giant cores by pebble accretion
• Building the Terrestrial Planets: Constrained Accretion in the Inner Solar System
• Formation of the Terrestrial Planets from a Narrow Annulus
• Oxygen isotopic evidence for vigorous mixing during the Moon-forming Giant Impact
• Three-dimensional simulations of multiple protoplanets embedded in a protostellar disc
• Highly Siderophile Elements in the Earth's Mantle as a Clock for the Moon-forming Impact
• REBOUNDx: A Library for Adding Conservative and Dissipative Forces to Otherwise Symplectic N-body Integrations
• Melting and Mixing States of the Earth's Mantle after the Moon-Forming Impact
• Mars' Growth Stunted by an Early Giant Planet Instability
• Hybrid Symplectic Integrators for Planetary Dynamics
• Constructing the secular architecture of the solar system II: The terrestrial planets
• Terrestrial planet formation from lost inner solar system material
• The Frequency of Giant impacts on Earth-like Worlds
• How planetary growth outperforms migration
• On the Migration of Jupiter and Saturn: Constraints from Linear Models of Secular Resonant Coupling with the Terrestrial Planets
• Three-dimensional Disk-Planet Torques in a Locally Isothermal Disk
• The early instability scenario: terrestrial planet formation during the giant planet instability, and the effect of collisional fragmentation
• Planetary Giant Impacts: Convergence of High-Resolution Simulations using Efficient Spherical Initial Conditions and SWIFT
• Nucleation and growth of iron pebbles explains the formation of iron-rich planets akin to Mercury
• Tidal Evolution of the Evection Resonance/Quasi-Resonance and the Angular Momentum of the Earth-Moon System
• Enhanced mixing in giant impact simulations with a new Lagrangian method
• Primordial Earth mantle heterogeneity caused by the Moon-forming giant impact
• Large planets may not form fractionally large moons
• A scaling relation for core heating by giant impacts and implications for dynamo onset
• Extreme close encounters between proto-Mercury and proto-Venus in terrestrial planet formation
• The Limited Role of the Streaming Instability During Moon and Exomoon Formation
• Hypothetical hyperbolic encounters between Venus and proto-Mercury that partially \ stripped away proto-Mercury's mantle
• Planetesimal Growth in Evolving Protoplanetary Disks: Constraints from the Pebble Supply