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Making Earths: a Statistical Approach to Post-Collisional Debris.

Presentation #102.40 in the session Poster Session.

Published onJun 20, 2022
Making Earths: a Statistical Approach to Post-Collisional Debris.

During the last phases of planet formation, the innermost part of planetary system is populated by Moon to Mars-size rocky objects called planetary embryos. While the process that leads to the formation of these objects is still under investigation, it is widely accepted that the subsequent mutual collisions among them play a key role in the final structure and composition of the planetary system. During the collision, a fraction of the total mass involved can be ejected in the form of debris, in particular volatile materials like water. It has been shown in different works that a significant part of the total embryos’ mass can be converted into debris.

While planetary collisions are well described by state-of-the-art SPH simulations, the problem of including collisional debris in N-body simulators is far from being solved. Several solutions have been proposed, the most sophisticated of which incorporates the collisional debris into the simulation by clustering them into a few new bodies. However, in order to keep the total number of bodies in the simulation reasonably small, these new bodies are all generated with the same mass, usually of the order of one lunar mass. Another possible approach is to consider the debris as unresolved material that can be accreted by the fully resolved bodies. Although this second method is capable of better describing the statistical effect of small debris, the orbits of the unresolved material have always been assumed to be circular and coplanar, and they have always been confined into circular bins of fixed width. However, recent studies on the statistical properties of collisional debris have shown that the mass and orbital distributions of this material can play a significant role in the orbital and chemical evolution of terrestrial planets.

Here we present the results our work in which we improved the unresolved-debris method by better modelling the debris distribution and the effect that such distribution has on the resolved bodies. To do so we performed N-body simulations of terrestrial planets formation in which the collisions are solved by interpolating a dataset of SPH simulations, and debris are included in the simulations as actual bodies. We also performed a comparative test between our improved version of the unresolved-debris method, the “standard” unresolved-debris method, and the method for which the debris are clustered into few Moon-size bodies. We show how and in which extent the simulation outcome, in particular the mass and composition of the formed planets, is affected by the method chosen to incorporate post-collisional debris in the simulation.


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