Climates of Warm Earth-like Planets II: Rotational 'Goldilocks' Zones for Fractional Habitability and Silicate Weathering

TL;DR

This study investigates how the rotation rate of Earth-like planets influences their habitability and silicate weathering, revealing optimal rotation periods for climate stability and potential habitability.

Contribution

It introduces a model-based analysis of rotational effects on fractional habitability and weathering, highlighting the importance of rotation period in planetary climate stability.

Findings

Maximum fractional habitability at 8-32 times Earth's day length.

Silicate weathering peaks around a 4-day rotation period.

Habitability and weathering are strongly affected by planetary rotation.

Abstract

Planetary rotation rate has a significant effect on atmospheric circulation, where the strength of the Coriolis effect in part determines the efficiency of latitudinal heat transport, altering cloud distributions, surface temperatures, and precipitation patterns. In this study we use the ROCKE-3D dynamic-ocean general circulation model to study the effects of slow rotations and increased insolations on the 'fractional habitability' and silicate weathering rate of an Earth-like world. Defining the fractional habitability f_h to be the percentage of a planet's surface which falls in the 0 <= T <= 100 C temperature regime, we find a moderate increase in f_h with a 10% and 20% increase in insolation and a possible maximum in f_h at sidereal day-lengths between 8 and 32 times that of the modern Earth. By tracking precipitation and run-off we further determine that there is a rotational regime centered on a 4-day period in which the silicate weathering rate is maximized and is particularly strongly peaked at higher overall insolations. Because of weathering's integral role in the long-term carbonate-silicate cycle, we suggest that climate stability may be strongly affected by the anticipated rotational evolution of temperate terrestrial-type worlds, and should be considered a major factor in their study. In light of our results we argue that planetary rotation period is an important factor to consider when determining the habitability of terrestrial worlds.