Rocky Histories: The Effect Of High Excitations On The Formation Of Rocky Planets

By Keith Cowing
Press Release
November 21, 2022
Filed under , , , ,
Rocky Histories: The Effect Of High Excitations On The Formation Of Rocky Planets
Impact angle and impact to escape velocity ratio of all the collisions in the simulated runs. The size of the points corresponds to the total colliding mass of the collision. The collisions in the simulations cover the entire parameter space of collision velocities and angles. Early on in the formation process, when embryos are small, there are large numbers of supercatastrophic collisions. The distribution of collisions for larger embryos later on in the formation process sticks to lower velocities and other, less destructive collision types. — astro-ph.EP

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 undergo 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 M⊕. Additionally, we find 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.

Jennifer Scora, Diana Valencia, Alessandro Morbidelli, Seth Jacobson

Comments: 19 pages. This is the version of the article before peer review or editing, as submitted to ApJ. This paper has been accepted to ApJ with some revisions
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2211.10491 [astro-ph.EP] (or arXiv:2211.10491v1 [astro-ph.EP] for this version)
Submission history
From: Jennifer Scora
[v1] Fri, 18 Nov 2022 19:57:37 UTC (6,519 KB)

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