A proposal for climate stability on H2-greenhouse planets

TL;DR

This paper proposes a climate feedback mechanism for H2-greenhouse planets, where biological processes help stabilize surface temperatures, making such planets more promising for habitability and astrobiology.

Contribution

It introduces a novel stabilizing climate feedback model involving biological H2 consumption on H2-rich planets, enhancing their habitability prospects.

Findings

Biological H2 consumption can stabilize planetary climate.

H2-warmed planets are promising astrobiological targets.

Climate feedbacks depend on biological activity and H2 fluxes.

Abstract

A terrestrial planet in an orbit far outside of the standard habitable zone could maintain surface liquid water as a result of H2-H2 collision-induced absorption by a thick H2 atmosphere. Without a stabilizing climate feedback, however, habitability would be accidental and likely brief. In this letter I propose stabilizing climate feedbacks for such a planet that require only that biological functions have an optimal temperature and operate less efficiently at other temperatures. For example, on a planet with a net source of H2 from its interior, H2-consuming life (such as methanogens) could establish a stable climate. If a positive perturbation is added to the equilibrium temperature, H2 consumption by life will increase (cooling the planet) until the equilibrium climate is reestablished. The potential existence of such feedbacks makes H2-warmed planets more attractive astrobiological targets.