Exoplanetology: Exoplanets & Exomoons

Formation Of Terrestrial Planets

By Keith Cowing

Status Report

astro-ph.EP

November 18, 2024

Filed under astro-ph.EP, Earth, exoplanet, Mars, planetary embryos, Terrestrial Planet, Venus

Formation Of Terrestrial Planets — Snapshots showing the dynamical evolution of the Solar System in the Grand Tack model. The four gas giants are represented by the black filled circles. Jupiter starts fully formed while the other giants planets grow. Terrestrial planetary embryos are represented by open circles. Water-rich and water-poor planetesimals/asteroids are shown by blue and red small dots, respectively. During the inward migration phase Jupiter shepherds planetesimals and planetary embryos, thus creating a confined disk around 1 AU. Saturn encounters Jupiter and both planets start to migrate outwards at about 100 kyr. During the outward migration phase the giant planets scatter planetesimals inward and repopulate the previously depleted belt with a mix of asteroids originated from different regions. Figure reproduced from Walsh et al. (2011). — astro-ph.EP

Our understanding of the process of terrestrial planet formation has grown markedly over the past 20 years, yet key questions remain. This review begins by first addressing the critical, earliest stage of dust coagulation and concentration.

While classic studies revealed how objects that grow to ∼meter sizes are rapidly removed from protoplanetary disks via orbital decay (seemingly precluding growth to larger sizes), this chapter addresses how this is resolved in contemporary, streaming instability models that favor rapid planetesimal formation via gravitational collapse of solids in over-dense regions.

Once formed, planetesimals grow into Mars-Earth-sized planetary embryos by a combination of pebble- and planetesimal accretion within the lifetime of the nebular disk. After the disk dissipates, these embryos typically experience a series of late giant impacts en route to attaining their final architectures.

This review also highlights three different inner Solar System formation models that can match a number of empirical constraints, and also reviews ways that one or more might be ruled out in favor of another in the near future.

These include (1) the Grand Tack, (2) the Early Instability and (3) Planet Formation from Rings. Additionally, this chapter discusses formation models for the closest known analogs to our own terrestrial planets: super-Earths and terrestrial exoplanets in systems also hosting gas giants. Finally, this review lays out a chain of events that may explain why the Solar System looks different than more than 99% of exoplanet systems.

Matthew S. Clement, Andre Izidoro, Sean N. Raymond, Rogerio Deienno

Comments: To be published in: Handbook of Exoplanets, 2nd Edition, Hans Deeg and Juan Antonio Belmonte (Eds. in Chief), Springer International Publishing AG, part of Springer Nature. 75 pages, 9 figures. This is an update of arXiv:1803.08830
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2411.03453 [astro-ph.EP] (or arXiv:2411.03453v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2411.03453
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Submission history
From: Matthew Clement
[v1] Tue, 5 Nov 2024 19:08:54 UTC (7,497 KB)
https://arxiv.org/abs/2411.03453

Astrobiology

Keith Cowing

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻

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