The Ability of Significant Tidal Stress to Initiate Plate Tectonics

TL;DR

This paper investigates how significant tidal stresses from host stars can initiate plate tectonics on rocky exoplanets, suggesting close-in planets are more likely to have active tectonics, which impacts their habitability.

Contribution

It introduces a model showing tidal stresses can overcome lithospheric yield stress, highlighting their role in initiating plate tectonics on exoplanets near their stars.

Findings

Tidal stresses from host stars can be comparable to mantle convection stresses.

Planet-planet tidal interactions are unlikely to trigger tectonics but may cause earthquakes.

Close-in exoplanets are more likely to experience active plate tectonics.

Abstract

Plate tectonics is a geophysical process currently unique to Earth, has an important role in regulating the Earth's climate, and may be better understood by identifying rocky planets outside our solar system with tectonic activity. The key criterion for whether or not plate tectonics may occur on a terrestrial planet is if the stress on a planet's lithosphere from mantle convection may overcome the lithosphere's yield stress. Although many rocky exoplanets closely orbiting their host stars have been detected, all studies to date of plate tectonics on exoplanets have neglected tidal stresses in the planet's lithosphere. Modeling a rocky exoplanet as a constant density, homogeneous, incompressible sphere, we show the tidal stress from the host star acting on close-in planets may become comparable to the stress on the lithosphere from mantle convection. We also show that tidal stresses from planet-planet interactions are unlikely to be significant for plate tectonics, but may be strong enough to trigger Earthquakes. Our work may imply planets orbiting close to their host stars are more likely to experience plate tectonics, with implications for exoplanetary geophysics and habitability. We produce a list of detected rocky exoplanets under the most intense stresses. Atmospheric and topographic observations may confirm our predictions in the near future. Investigations of planets with significant tidal stress can not only lead to observable parameters linked to the presence of active plate tectonics, but may also be used as a tool to test theories on the main driving force behind tectonic activity.