Habitability from Tidally-Induced Tectonics

TL;DR

This paper introduces a vertical recycling tectonic mechanism driven by tidal heating, which can stabilize climate and support habitability on planets around M stars, especially those with lower carbon budgets.

Contribution

It proposes a novel tidally-induced tectonic process enabling long-term climate stability, expanding potential habitability scenarios beyond Earth-like plate tectonics.

Findings

Vertical recycling can sustain temperate climates over billions of years.

Planets with lower carbon content are more likely to maintain habitable conditions.

Tidally-driven tectonics may explain habitability of planets like those in Trappist-1.

Abstract

The stability of Earth's climate on geological timescales is enabled by the carbon-silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgas of atmospheric carbon. On Earth, this thermostat is enabled by plate tectonics that sequesters outgassed CO2 back into the mantle via weathering and subduction at convergent margins. Here we propose a separate tectonic mechanism -- vertical recycling -- that can serve as the vehicle for CO2 outgassing and sequestration over long timescales. The mechanism requires continuous tidal heating, which makes it particularly relevant to planets in the habitable zone of M stars. Dynamical models of this vertical recycling scenario and stability analysis show that temperate climates stable over Gy timescales are realized for a variety of initial conditions, even as the M star dims over time. The magnitude of equilibrium surface temperatures depends on the interplay of sea weathering and outgassing, which in turn depends on planetary carbon content, so that planets with lower carbon budgets are favoured for temperate conditions. Habitability of planets such as found in the Trappist-1 may be rooted in tidally-driven tectonics.