09/setembro/22 – Mercury formation from a giant impact involving similar size bodies (MSc Patrick Franco, ON )

The planet Mercury is predominantly made up of an iron core covered by a thin layer of silicates, which has led to the idea that this configuration is the product of a giant impact. In particular, the impact called classic hit-and-run has been explored, in which a proto-Mercury with mass ~ 0.1 ME collides with a target with mass ~1 ME, losing part of the material of its mantle. Simulations of the formation of terrestrial planets, using numerical algorithms of N-bodies, have been shown to be incapable of producing an object with the characteristics of Mercury. Part of this limitation is due to the fact that, in this type of simulation, collisions are always treated as inelastic, making the resulting body mass the sum of the masses of the two colliding bodies. Furthermore, we observe that configurations that seek to explain Mercury by a giant impact such as those required by the classic hit-and-run scenario are rare, even when there are a lot of collisions on the accretion disk. On the other hand, we found that hit-and-run collisions, different from the classical scenario, in which the target and projectile masses are similar, occur much more frequently in N-body simulations. In this work, we aim to investigate whether this last type of collision can favor the formation of Mercury using smoothed hydrodynamic simulations (SPH). Our results indicate that considering targets with masses similar to that of proto-Mercury, it is possible to obtain the desired result as long as the impact energy is sufficiently high, but still compatible with the values observed in the N-body simulations.