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Title: COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION

Abstract

Numerical simulations of the stochastic end stage of planet formation typically begin with a population of embryos and planetesimals that grow into planets by merging. We analyzed the impact parameters of collisions leading to the growth of terrestrial planets from recent N-body simulations that assumed perfect merging and calculated more realistic outcomes using a new analytic collision physics model. We find that collision outcomes are diverse and span all possible regimes: hit-and-run, merging, partial accretion, partial erosion, and catastrophic disruption. The primary outcomes of giant impacts between planetary embryos are approximately evenly split between partial accretion, graze-and-merge, and hit-and-run events. To explore the cumulative effects of more realistic collision outcomes, we modeled the growth of individual planets with a Monte Carlo technique using the distribution of impact parameters from N-body simulations. We find that fewer planets reached masses >0.7 M{sub Earth} using the collision physics model compared to simulations that assumed every collision results in perfect merging. For final planets with masses >0.7 M{sub Earth}, 60% are enriched in their core-to-mantle mass fraction by >10% compared to the initial embryo composition. Fragmentation during planet formation produces significant debris ({approx}15% of the final mass) and occurs primarily by erosion of themore » smaller body in partial accretion and hit-and-run events. In partial accretion events, the target body grows by preferentially accreting the iron core of the projectile and the escaping fragments are derived primarily from the silicate mantles of both bodies. Thus, the bulk composition of a planet can evolve via stochastic giant impacts.« less

Authors:
 [1]
  1. Department of Earth and Planetary Sciences, Harvard University, 20 Oxford Street, Cambridge, MA 02138 (United States)
Publication Date:
OSTI Identifier:
22037263
Resource Type:
Journal Article
Journal Name:
Astrophysical Journal
Additional Journal Information:
Journal Volume: 751; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0004-637X
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COLLISIONS; COMPUTERIZED SIMULATION; EROSION; FRAGMENTATION; GRAVITATION; IMPACT PARAMETER; IRON; MASS; MONTE CARLO METHOD; PLANETS; SILICATES; STOCHASTIC PROCESSES

Citation Formats

Stewart, Sarah T, and Leinhardt, Zoee M., E-mail: sstewart@eps.harvard.edu, E-mail: zoe.leinhardt@bristol.ac.uk. COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION. United States: N. p., 2012. Web. doi:10.1088/0004-637X/751/1/32.
Stewart, Sarah T, & Leinhardt, Zoee M., E-mail: sstewart@eps.harvard.edu, E-mail: zoe.leinhardt@bristol.ac.uk. COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION. United States. https://doi.org/10.1088/0004-637X/751/1/32
Stewart, Sarah T, and Leinhardt, Zoee M., E-mail: sstewart@eps.harvard.edu, E-mail: zoe.leinhardt@bristol.ac.uk. Sun . "COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION". United States. https://doi.org/10.1088/0004-637X/751/1/32.
@article{osti_22037263,
title = {COLLISIONS BETWEEN GRAVITY-DOMINATED BODIES. II. THE DIVERSITY OF IMPACT OUTCOMES DURING THE END STAGE OF PLANET FORMATION},
author = {Stewart, Sarah T and Leinhardt, Zoee M., E-mail: sstewart@eps.harvard.edu, E-mail: zoe.leinhardt@bristol.ac.uk},
abstractNote = {Numerical simulations of the stochastic end stage of planet formation typically begin with a population of embryos and planetesimals that grow into planets by merging. We analyzed the impact parameters of collisions leading to the growth of terrestrial planets from recent N-body simulations that assumed perfect merging and calculated more realistic outcomes using a new analytic collision physics model. We find that collision outcomes are diverse and span all possible regimes: hit-and-run, merging, partial accretion, partial erosion, and catastrophic disruption. The primary outcomes of giant impacts between planetary embryos are approximately evenly split between partial accretion, graze-and-merge, and hit-and-run events. To explore the cumulative effects of more realistic collision outcomes, we modeled the growth of individual planets with a Monte Carlo technique using the distribution of impact parameters from N-body simulations. We find that fewer planets reached masses >0.7 M{sub Earth} using the collision physics model compared to simulations that assumed every collision results in perfect merging. For final planets with masses >0.7 M{sub Earth}, 60% are enriched in their core-to-mantle mass fraction by >10% compared to the initial embryo composition. Fragmentation during planet formation produces significant debris ({approx}15% of the final mass) and occurs primarily by erosion of the smaller body in partial accretion and hit-and-run events. In partial accretion events, the target body grows by preferentially accreting the iron core of the projectile and the escaping fragments are derived primarily from the silicate mantles of both bodies. Thus, the bulk composition of a planet can evolve via stochastic giant impacts.},
doi = {10.1088/0004-637X/751/1/32},
url = {https://www.osti.gov/biblio/22037263}, journal = {Astrophysical Journal},
issn = {0004-637X},
number = 1,
volume = 751,
place = {United States},
year = {2012},
month = {5}
}