Coupling SPH and thermochemical models of planets: Methodology and example of a Mars-sized body

TL;DR

This paper introduces a novel methodology combining 3-D shock physics and thermochemical models to study the long-term interior evolution of planets after giant impacts, demonstrated on a Mars-sized body.

Contribution

It presents an integrated 3-D approach to model planetary impact effects and interior evolution, highlighting the importance of impact angle on crustal distribution.

Findings

Impact angle critically influences crustal patterns after collisions.

Grazing impacts lead to different crustal distributions compared to head-on collisions.

Material parameters affect long-term evolution but are less influential than impact angle.

Abstract

Giant impacts have been suggested to explain various characteristics of terrestrial planets and their moons. However, so far in most models only the immediate effects of the collisions have been considered, while the long-term interior evolution of the impacted planets was not studied. Here we present a new approach, combining 3-D shock physics collision calculations with 3-D thermochemical interior evolution models. We apply the combined methods to a demonstration example of a giant impact on a Mars-sized body, using typical collisional parameters from previous studies. While the material parameters (equation of state, rheology model) used in the impact simulations can have some effect on the long-term evolution, we find that the impact angle is the most crucial parameter for the resulting spatial distribution of the newly formed crust. The results indicate that a dichotomous crustal pattern can form after a head-on collision, while this is not the case when considering a more likely grazing collision. Our results underline that end-to-end 3-D calculations of the entire process are required to study in the future the effects of large-scale impacts on the evolution of planetary interiors.