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

Abstract

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 around 1% of the target's mass. 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. Slow atmosphere-hosting impactors can also deliver a significant mass of atmosphere, but always accompanied by larger proportions of their mantle and core. Different Moon-forming impact hypotheses suggest that around 10 to 60% of a primordial atmosphere could have been removed directly, depending on the scenario. We find no evident departure from the scaling trends at the extremes of the parameters explored. The scaling law can be incorporated readily into models of planet formation.

Published in ApJL. 12 pages, 6 figures

References in corpus (3)

• Evidence for multiple magma ocean outgassing and atmospheric loss episodes from mantle noble gases
• Atmosphere loss in planet-planet collisions
• Outcomes of Grazing Impacts Between Sub-Neptunes in Kepler Multis

Cited by in corpus (8)

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• A recent impact origin of Saturn's rings and mid-sized moons
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• Formation of giant planets with large metal masses and metal fractions via giant impacts in a rapidly dissipating disk
• Atmosphere Loss in Oblique Super-Earth Impacts
• Protoplanet Collisions: Statistical Properties of Ejecta
• Takeout and Delivery: Erasing the Dusty Signature of Late-stage Terrestrial Planet Formation