Seminar – Jacob Kegerreis

Speaker: Jacob Kegerreis, Institute for Computational Cosmology, Durham University

Title: Atmospheric Erosion (and more!) by Giant Impacts onto Terrestrial Planets

Abstract: Giant impacts dominate many planets’ late accretion and evolution, including the Earth’s, and can build, erode, or completely destroy a young atmosphere. In this talk, I’ll present how we use 3D simulations to examine the erosion and other consequences of these collisions. For example, in the Moon-forming impact, only around 10% of the atmosphere would have been lost from the immediate effects of a ‘canonical’ impact, up to about 60% in more violent scenarios. We find a 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 broadly terrestrial planets with relatively thin 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, and is independent of the total system mass for a constant impactor:total mass ratio. Slow impactors can also deliver a significant mass of atmosphere, but always accompanied by larger proportions of their mantle and core. Lastly, I’ll show how these high-resolution simulations reveal an alternate route for the origin of the Moon as an immediate post-impact satellite in orbit.

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