Atmosphere loss in planet-planet collisions

Thomas R. Denman*, Zoe M. Leinhardt, Philip J. Carter, Christoph Mordasini

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

4 Citations (Scopus)

Abstract

Many of the planets discovered by the Kepler satellite are close orbiting super-Earths or mini- Neptunes. Such objects exhibit a wide spread of densities for similar masses. One possible explanation for this density spread is giant collisions stripping planets of their atmospheres. In this paper, we present the results from a series of smoothed particle hydrodynamics (SPH) simulations of head-on collisions of planets with significant atmospheres and bare projectiles without atmospheres. Collisions between planets can have sufficient energy to remove substantial fractions of the mass from the target planet. We find the fraction of mass lost splits into two regimes - at low impact energies only the outer layers are ejected corresponding to atmosphere dominated loss, at higher energies material deeper in the potential is excavated resulting in significant core and mantle loss. Mass removal is less efficient in the atmosphere loss dominated regime compared to the core and mantle loss regime, due to the higher compressibility of atmosphere relative to core and mantle. We find roughly 20 per cent atmosphere remains at the transition between the two regimes. We find that the specific energy of this transition scales linearly with the ratio of projectile to target mass for all projectile-target mass ratios measured. The fraction of atmosphere lost is well approximated by a quadratic in terms of the ratio of specific energy and transition energy. We provide algorithms for the incorporation of our scaling law into future numerical studies.

Original languageEnglish
Pages (from-to)1166-1181
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume496
Issue number2
DOIs
Publication statusPublished - 2020

Bibliographical note

Funding Information:
This work was carried out using the computational facilities of the Advanced Computing Research Centre, University of Bristol – http://www.bristol.ac.uk/acrc/. Thomas R. Denman acknowledges support from an STFC (Science and Technologies Facilities Council) studentship. Phil J. Carter acknowledges support from University of California Office of the President grant LFR-17-449059. Christoph Mordasini acknowledges support from the Swiss National Science Foundation under grant BSSGI0 155816 ‘PlanetsInTime’. Parts of this work have been carried out within the framework of the NCCR PlanetS (National Centre of Competence in Research PlanetS) supported by the Swiss National Science Foundation. This research has used the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.

Funding Information:
This work was carried out using the computational facilities of the Advanced Computing Research Centre, University of Bristol - http://www.bristol.ac.uk/acrc/. Thomas R. Denman acknowledges support from an STFC (Science and Technologies Facilities Council) studentship. Phil J. Carter acknowledges support from University of California Office of the President grant LFR- 17-449059. Christoph Mordasini acknowledges support from the Swiss National Science Foundation under grant BSSGI0 155816 'PlanetsInTime'. Parts of this work have been carried out within the framework of the NCCR PlanetS (National Centre of Competence in Research PlanetS) supported by the Swiss National Science Foundation. This research has used the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.

Publisher Copyright:
© 2020 The Author(s).

Keywords

  • Methods: numerical
  • Planets and satellites: atmospheres
  • Planets and satellites: dynamical evolution and stability
  • Planets and satellites: formation.

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