PLANETARY

Moon-forming Giant Impact

Understanding the evidence and long-term consequences of the last major accretion of Earth.

Research Overview

Earth’s evolution began 4.5 billion years ago with the Moon-forming impact between Earth and the hypothesized planet Theia. We explore whether continental-scale seismic anomalies are remnants of Theia’s mantle and how plumes from them may have triggered the earliest subduction.

Research Questions

Where is the missing impactor, Theia? What were the long-term tectonic consequences of the Giant Impact? Why is Earth unique in sustaining plate tectonics?

Methodology

We pioneered the integration of short-timescale (hour-scale) Moon-forming impact simulations with long-timescale (billion-year) mantle convection models, linking them through thermodynamic and seismic constraints. This framework enables us to connect energetic early impacts with the long-term evolution of Earth’s mantle. In addition, we employ fully 3D thermo-elasto-mechanical models to simulate deep mantle structure, plume generation, and plume-driven subduction in a self-consistent way.

Key Findings

1. Our canonical Moon-forming giant impact simulations show that the collision would have melted the upper half of Earth’s mantle. 2. Mantle convection models suggest that Theia’s material sank into the lower mantle, forming the Large Low Shear Velocity Provinces (LLSVPs) over 4.5 billion years. 3. Plumes from this reservoir may have triggered the earliest subduction, offering new clues to the Moon’s origin, mantle heterogeneities, and plate tectonics.