A proposal for climate stability on H2-greenhouse planets

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.

5 pages, 3 figures, accepted at ApJL

References in corpus (2)

• Biosignature Gases in H2-Dominated Atmospheres on Rocky Exoplanets
• Testing the Early Mars H2-CO2 Greenhouse Hypothesis with a 1-D Photochemical Model

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• Understanding planetary context to enable life detection on exoplanets and test the Copernican principle
• Robustness of Gaian Feedbacks to Climate Perturbations
• A Biotic Habitable Zone: Impacts of Adaptation in Biotic Temperature Regulation
• The continued importance of habitability studies