Exoplanets & Exomoons

Terrestrial Planet Formation From A Ring

By Keith Cowing
Status Report
March 1, 2023
Filed under , ,
Terrestrial Planet Formation From A Ring
Snapshots of mass versus semi-major axis for a simulation with a normal gas disc. The gas dissipation timescale, τdecay = 1 Myr and the mean initial location of the ring of planetesimals, μ = 1 AU. Thick black circles represent embryos with mass > 10-2 MEarth, blue circles represent intermediate size objects with mass in between smallest planetesimals (red circles) and embryos. All masses are self-gravitating and the colour difference is only for visualisation purposes. Different terrestrial planet regions are shaded (Mercury – grey; Venus – Orange; Earth – blue; Mars – red) according to the definition of Brasser et al. (2016). — astro-ph.EP

It has been long proposed that, if all the terrestrial planets form within a tiny ring of solid material at around 1 AU, the concentrated mass-distance distribution of the current system can be reproduced.

Recent planetesimal formation models also support this idea. In this study, we revisit the ring model by performing a number of high-resolution N-body simulations for 10 Myr of a ring of self-interacting planetesimals, with various radial distributions of the gas disc. We found that even if all the planetesimals form at ~1 AU in a minimum mass solar nebula-like disc, the system tends to spread radially as accretion proceeds, resulting in a system of planetary embryos lacking mass-concentration at ~1 AU.

Modifying the surface density of the gas disc into a concave shape with a peak at ~1 AU helps to maintain mass concentrated at ~1 AU and solve the radial dispersion problem. We further propose that such a disc should be short lived (<= 1 Myr) and with a shallower radial gradient in the innermost region (< 1 AU) than previously proposed to prevent a too-rapid growth of Earth.

Future studies should extend to ~100 Myr the most promising simulations and address in a self-consistent manner the evolution of the asteroid belt and its role in the formation of the terrestrial planets.

J. M. Y. Woo, A. Morbidelli, S. L. Grimm, J. Stadel, R. Brasser

Comments: Accepted by Icarus
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2302.14100 [astro-ph.EP] (or arXiv:2302.14100v1 [astro-ph.EP] for this version)
Submission history
From: Jason Man Yin Woo
[v1] Mon, 27 Feb 2023 19:21:16 UTC (1,376 KB)

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