Atmosphere loss in planet-planet collisions

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 twenty 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.

arXiv comment16 pages, 8 figures, accepted for publication in MNRAS, for associated mp4 files see http://www.star.bris.ac.uk/TDenman/Paper1_Videos/t6-25Me_p0-25Me_v2e6cms.mp4 , http://www.star.bris.ac.uk/TDenman/Paper1_Videos/t6-25Me_p2Me_v3e6cms.mp4 , http://www.star.bris.ac.uk/TDenman/Paper1_Videos/t6-25Me_p4Me_v5e6cms.mp4 and http://www.star.bris.ac.uk/TDenman/Paper1_Videos/t6-25Me_p5Me_v6e6cms.mp4

References in corpus (31)

• The cosmological simulation code GADGET-2
• Kepler planets: a tale of evaporation
• Understanding the Mass-Radius Relation for Sub-Neptunes: Radius as a Proxy for Composition
• Models of Giant Planet formation with migration and disc evolution
• Internal Structure of Massive Terrestrial Planets
• The Role of Core Mass in Controlling Evaporation: the Kepler Radius Distribution and the Kepler-36 Density Dichotomy
• Collisions Between Gravity-Dominated Bodies: 1. Outcome Regimes and Scaling Laws
• Collisions between Gravity-Dominated Bodies: 2. The Diversity of Impact Outcomes during the End Stage of Planet Formation
• How Thermal Evolution and Mass Loss Sculpt Populations of Super-Earths and Sub-Neptunes: Application to the Kepler-11 System and Beyond
• Gaseous Mean Opacities for Giant Planet and Ultracool Dwarf Atmospheres over a Range of Metallicities and Temperatures
• Planetary population synthesis coupled with atmospheric escape: a statistical view of evaporation
• Characterization of exoplanets from their formation I: Models of combined planet formation and evolution
• Discovery, Progenitor & Early Evolution of a Stripped Envelope Supernova iPTF13bvn
• Atmospheric Mass Loss During Planet Formation: The Importance of Planetesimal Impacts
• Collisional Stripping and Disruption of Super-Earths
• Are Planetary Systems Filled to Capacity? A Study Based on Kepler Results
• A giant impact as the likely origin of different twins in the Kepler-107 exoplanet system
• The structure of terrestrial bodies: Impact heating, corotation limits and synestias
• Stealing the Gas: Giant Impacts and the Large Diversity in Exoplanet Densities
• Predicting Planets in Known Extra-Solar Planetary Systems I: Test Particle Simulations
• Giant Impact: An Efficient Mechanism for the Devolatilization of Super-Earths
• Planetary population synthesis
• Grain opacity and the bulk composition of extrasolar planets. I. Results from scaling the ISM opacity
• Water/Icy Super-Earths: Giant Impacts and Maximum Water Content
• Consequences of Giant Impacts on Early Uranus for Rotation, Internal Structure, Debris, and Atmospheric Erosion
• Planetary Giant Impacts: Convergence of High-Resolution Simulations using Efficient Spherical Initial Conditions and SWIFT
• Collisional stripping of planetary crusts
• The energy budget and figure of Earth during recovery from the Moon-forming giant impact
• Outcomes of Grazing Impacts Between Sub-Neptunes in Kepler Multis
• Dynamics and Collisional Evolution of Closely Packed Planetary Systems
• Real-space characterization of reactivity towards water at Bi2Te3(111) surface

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