The Energy Budgets of Giant Impacts

Giant impacts dominate the final stages of terrestrial planet formation and set the configuration and compositions of the final system of planets. A giant impact is believed to be responsible for the formation of Earth's Moon, but the specific impact parameters are under debate. Because the can...

Full description

Saved in:
Bibliographic Details
Published in:Journal of geophysical research. Planets 2020-01, Vol.125 (1), p.n/a
Main Authors: Carter, P. J., Lock, S. J., Stewart, S. T.
Format: Article
Language:English
Subjects:
Accretion
Balancing
Configurations
Earth
Energy
Energy budget
Energy transfer
Entropy
Evolution
Giant impacts
Gravitation
Internal energy
Moon
Planet formation
Planetary composition
Planetary evolution
Potential energy
Star formation
Synestias
Terrestrial environments
Terrestrial planets
Vaporization
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Giant impacts dominate the final stages of terrestrial planet formation and set the configuration and compositions of the final system of planets. A giant impact is believed to be responsible for the formation of Earth's Moon, but the specific impact parameters are under debate. Because the canonical Moon‐forming impact is the most intensely studied scenario, it is often considered the archetypal giant impact. However, a wide range of impacts with different outcomes are possible. Here we examine the total energy budgets of giant impacts that form Earth‐mass bodies and find that they differ substantially across the wide range of possible Moon‐forming events. We show that gravitational potential energy exchange is important, and we determine the regime in which potential energy has a significant effect on the collision outcome. Energy is deposited heterogeneously within the colliding planets, increasing their internal energies, and portions of each body attain sufficient entropy for vaporization. After gravitational re‐equilibration, post‐impact bodies are strongly thermally stratified, with varying amounts of vaporized and supercritical mantle. The canonical Moon‐forming impact is a relatively low‐energy event and should not be considered the archetype of accretionary giant impacts that form Earth‐mass planets. After a giant impact, bodies are significantly inflated in size compared to condensed planets of the same mass, and there are substantial differences in the magnitudes of their potential, kinetic, and internal energy components. As a result, the conditions for metal‐silicate equilibration and the subsequent evolution of the planet may vary widely between different impact scenarios. Plain Language Summary Collisions between large planetary bodies, known as giant impacts, dominate the final stages of the formation of rocky planets like the Earth and set the configuration and compositions of the final planets. A giant impact is believed to have formed Earth's Moon, but the specific configuration of this impact is under debate. Understanding giant impacts is crucial for understanding the formation and evolution of the Earth and the Moon as well as rocky planets around other stars. The traditional Moon‐forming impact model is often considered the archetype of a giant impact; however, a wide range of impacts with substantially different outcomes are possible. In this work, we examine the total energies involved in giant impacts that form Earth‐like planets
ISSN:2169-9097
2169-9100
DOI:10.1029/2019JE006042