Peak shock conditions during Giant Impacts in terrestrial planets

Catastrophic events like giant impacts are abundant in the early stages of evolution of all planets. They can lead to planetary-scale disruption and as such they reset all geochemical clocks, they can partially or totally mix the two bodies involved in the collision, they can rip layers apart or form moons. The case of the terrestrial planets is more complicated because of the differentiation, which results in different layers that can behave differently.

Here we calculate the pressure and temperature conditions that can be reached during giant impacts. We consider model terrestrial planets that can be liquid, i.e. in the stage of global magma ocean, or solid, i.e. with three constitutive layers: crust, mantle, and core. In our model, the global magma ocean has pyrolitic composition; in case of solid planets, the crust is formed of silica or feldspars, the mantle of pyrolite, and the core of iron. To obtain the shock conditions we calculate the Hugoniot equations of state from first-principles molecular-dynamics simulations in the VASP implementation. We use this information to discuss the initial conditions of protolunar disks/synestias and the possibility of partial vaporization.

This work was supported by the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement number 681818 IMPACT awarded to RC) and by grant NNSA DE-NA000384.