Atmospheric Erosion by Giant Impacts onto Terrestrial Planets

Kegerreis, J.A.; Eke, V.R.; Massey, R.J.; Teodoro, L.F.A.

Abstract

We examine the mechanisms by which the atmosphere can be eroded by giant impacts onto Earth-like planets with thin atmospheres, using 3D smoothed particle hydrodynamics simulations with sufficient resolution to directly model the fate of low-mass atmospheres. We present a simple scaling law to estimate the fraction lost for any impact angle and speed in this regime. In the canonical Moon-forming impact, only around 10% of the atmosphere would have been lost from the immediate effects of the collision. There is a gradual transition from removing almost none to almost all of the atmosphere for a grazing impact as it becomes more head-on or increases in speed, including complex, nonmonotonic behavior at low impact angles. In contrast, for head-on impacts, a slightly greater speed can suddenly remove much more atmosphere. Our results broadly agree with the application of 1D models of local atmosphere loss to the ground speeds measured directly from our simulations. However, previous analytical models of shock-wave propagation from an idealized point-mass impact significantly underestimate the ground speeds and hence the total erosion. The strong dependence on impact angle and the interplay of multiple nonlinear and asymmetrical loss mechanisms highlight the need for 3D simulations in order to make realistic predictions.

Citation

Kegerreis, J., Eke, V., Massey, R., & Teodoro, L. (2020). Atmospheric Erosion by Giant Impacts onto Terrestrial Planets. Astrophysical Journal, 897(2), Article 161. https://doi.org/10.3847/1538-4357/ab9810

• Journal Article Type: Article
• Acceptance Date: May 28, 2020
• Online Publication Date: Jul 15, 2020
• Publication Date: 2020-07
• Deposit Date: Jul 21, 2020
• Publicly Available Date: Jul 21, 2020
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 897
• Issue: 2
• Article Number: 161
• DOI: https://doi.org/10.3847/1538-4357/ab9810
• Public URL: https://durham-repository.worktribe.com/output/1266152
• Related Public URLs: https://arxiv.org/abs/2002.02977