Atmospheric Erosion By Giant Impacts Onto Terrestrial Planets: A Scaling Law for any Speed, Angle, Mass, and Density

Illustrative snapshot cross-sections from four example impact simulations, using ∼107.5 SPH particles. The annotations detail the parameters for each scenario (see §2 and Fig. 1); the lost mass fraction of the atmosphere, X; and the time. Note that the snapshots are at different times to show the evolution in each case. In the left-most panels, the particles that will become unbound and escape the system are highlighted in purple on a pre-impact snapshot. Grey and orange show the target’s core and mantle material respectively, and brown and yellow show the same for the impactor. Blue is the target’s atmosphere. The colour luminosity varies slightly with the internal energy.

We present a new scaling law to predict the loss of atmosphere from planetary collisions for any speed, angle, impactor mass, target mass, and body compositions, in the regime of giant impacts onto broadly terrestrial planets with relatively thin atmospheres.

To this end, we examine the erosion caused by a wide range of impacts, using 3D smoothed particle hydrodynamics simulations with sufficiently high resolution to directly model the fate of low-mass atmospheres. Different collision scenarios lead to extremely different behaviours and consequences for the planets.

In spite of this complexity, the fraction of lost atmosphere is fitted well by a power law. Scaling is independent of the system mass for a constant impactor mass ratio. We find no evident departure from the trend at the extremes of the parameters explored. The scaling law can readily be incorporated into models of planet formation.

Jacob A. Kegerreis, Vincent R. Eke, David C. Catling, Richard J. Massey, Luis F. A. Teodoro, Kevin J. Zahnle
Comments: Submitted to ApJ. 12 pages, 5 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2007.04321 [astro-ph.EP] (or arXiv:2007.04321v1 [astro-ph.EP] for this version)
Submission history
From: Jacob Kegerreis
[v1] Wed, 8 Jul 2020 18:00:01 UTC (2,472 KB)

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