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The effect of high excitations on the composition of rocky planets

Presentation #102.05 in the session Formation of Planets and Satellites.

Published onOct 20, 2022
The effect of high excitations on the composition of rocky planets

Rocky planets both in and outside of our solar system are observed to have a range of core-mass fractions (CMFs). Imperfect collisions can preferentially strip mantle material from a planet, changing its CMF, and are therefore thought to be the most likely cause of this observed CMF variation. However, previous work that implements these collisions into N-body simulations of planet formation has struggled to reliably form high CMF super-Earths. In this work, we specify our initial conditions and simulation parameters to maximize the prevalence of high-energy, CMF-changing collisions in order to form planets with highly diverse CMFs. High-energy collisions have a large vimp/vesc ratio, so we maximize this ratio by starting simulations with high-eccentricity and inclination disks to increase the difference in their orbital velocities, maximizing vimp. Additionally, we minimize vesc by starting with small embryos. The final planets experience more high-energy, debris-producing collisions, and experience significant CMF change over their formation. However, we find that a number of processes work together to average out the CMF of a planet over time, therefore we do not consistently form high-CMF, high mass planets. We do form high-CMF planets below 0.5 MEarth. Additionally, we find that in these highly eccentric environments, loss of debris mass due to collisional grinding has a significant effect on final planet masses and CMFs, resulting in smaller planets and a higher average planet CMF. This work highlights the importance of improving measurements of high-density planets to better constrain their CMFs.

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