Formation of Mercury by a grazing giant collision involving similar-mass bodies

Abstract

The origin of Mercury still remains poorly understood compared with the other rocky planets of the Solar System. To explain its internal structure, it is usually considered to be the product of a giant impact. However, most studies assume a binary collision between bodies of substantially different masses, which seems to be unlikely according to N-body simulations. Here, we perform smoothed-particle hydrodynamics simulations to investigate the conditions under which collisions of similar-mass bodies are able to form a Mercury-like planet. Our results show that such collisions can fulfil the necessary constraints in terms of mass (0.055 M⊕) and composition (30/70 silicate-to-iron mass ratio) within less than 5%, as long as the impact angles and velocities are properly adjusted according to well established scaling laws. With these results, we broaden the scope of plausible formation scenarios by presenting those that are more frequent in numerical simulations, less constrained in planetary contexts and thus more likely to happen.