Astrogeology

Some Tectonic Concepts Relevant to the Study of Rocky Exoplanets

By Keith Cowing

Status Report

astro-ph.EP

April 27, 2024

Filed under astrogeology, exoplanet, geology, Plate Tectonics

Some Tectonic Concepts Relevant to the Study of Rocky Exoplanets — Illustration of plate tectonic features and mantle convection on Earth. Mid-ocean spreading ridges and the transform faults that offset such are shown, as is a subduction zone, the dewatering of the subducted slab that drives partial melting of the mantle wedge, and the volcanic arc that is produced as a result. Also shown is a hot upwelling plume that is rooted at the core/mantle boundary (the only significant thermal boundary layer below Earth’s surface) that also drives partial melting in the mantle and volcanism at the surface (at so-called “hot spots”). Note that convection is dominated by plume upwellings and downwelling tectonic plates; this whole-mantle flow has no connection to spreading ridges. Spreading ridges are a result of passive upwelling of the mantle as the plates are ripped apart by far-field forces, but are not connected to the deeper, hotter mantle. See Silver et al. (1988) and Davies and Richards (1992). — astro-ph.EP

We’ll examine plate tectonics on Earth — its features and forces — and examine some concepts that may allow astronomers to ask useful questions regarding numeric models that putatively predict tectonic activity.

But exo-planetologists should be aware that geologists are still attempting to understand: why does Earth operates as it does, and so much differently than its neighbors? Has it always operated this way and have other planets of the inner Solar System ever mimicked Earth’s behavior in their past? These problems are unsolved, though some interesting speculative notions have emerged.

Studies by Foley et al. et al. (2012) and Weller and Lenardic (2018), for example, attempt to distill the essential planetary properties that may influence if not dictate possible tectonic states, while Yin et al. (2016) propose a model of planetary tectonic surface features that appears remarkably precise. These studies yield some compelling expedients for analyses of planetary objects both within and outside our Solar System.

Keith D. Putirka

Comments: Chapter 9 accepted for publication in the Reviews in Mineralogy and Geochemistry (RiMG) Volume 90 on “Exoplanets: Compositions, Mineralogy, and Evolution” edited by Natalie Hinkel, Keith Putirka, and Siyi Xu; 18 pages, 4 figures, 1 table, and 7 equations
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR); Geophysics (physics.geo-ph)
Cite as: arXiv:2404.15428 [astro-ph.EP] (or arXiv:2404.15428v1 [astro-ph.EP] for this version)
Submission history
From: Keith D. Putirka [via Natalie Hinkel as proxy]
[v1] Tue, 23 Apr 2024 18:19:16 UTC (1,782 KB)
https://arxiv.org/abs/2404.15428

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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