Titania may produce abiotic oxygen atmospheres on habitable exoplanets

Abstract

The search for habitable exoplanets in the Universe is actively ongoing in the field of astronomy. The biggest future milestone is to determine whether life exists on such habitable exoplanets. In that context, oxygen in the atmosphere has been considered strong evidence for the presence of photosynthetic organisms. In this paper, we show that a previously unconsidered photochemical mechanism by titanium(IV) oxide (titania) can produce abiotic oxygen from liquid water under near ultraviolet (NUV) lights on the surface of exoplanets. Titania works as a photocatalyst to dissociate liquid water in this process. This mechanism offers a different source of a possibility of abiotic oxygen in atmospheres of exoplanets from previously considered photodissociation of water vapor in upper atmospheres by extreme ultraviolet (XUV) light. Our order-of-magnitude estimation shows that possible amounts of oxygen produced by this abiotic mechanism can be comparable with or even more than that in the atmosphere of the current Earth, depending on the amount of active surface area for this mechanism. We conclude that titania may act as a potential source of false signs of life on habitable exoplanets.

Published in Scientific Reports, open access version is available from http://www.nature.com/articles/srep13977

References in corpus (6)

• The Transiting Exoplanet Survey Satellite
• Extreme Water Loss and Abiotic O${}_2$ Buildup On Planets Throughout the Habitable Zones of M Dwarfs
• An Earth-sized Planet in the Habitable Zone of a Cool Star
• Abiotic oxygen-dominated atmospheres on terrestrial habitable zone planets
• Abiotic Ozone and Oxygen in Atmospheres Similar to Prebiotic Earth
• The Near-Ultraviolet Luminosity Function of Young, Early M-Type Dwarf Stars

Cited by in corpus (10)

• Exoplanet Biosignatures: Understanding Oxygen as a Biosignature in the Context of Its Environment
• Telling twins apart: Exo-Earths and Venuses with transit spectroscopy
• Physical constraints for the evolution of life on exoplanets
• Dust in brown dwarfs and extra-solar planets. VII. Cloud formation in diffusive atmospheres
• Red-edge position of habitable exoplanets around M-dwarfs
• Theoretical Reflectance Spectra of Earth-Like Planets through Their Evolutions: Impact of Clouds on the Detectability of Oxygen, Water, and Methane with Future Direct Imaging Missions
• From climate models to planetary habitability: temperature constraints for complex life
• Testing Earth-like atmospheric evolution on exo-Earths through oxygen absorption: required sample sizes and the advantage of age-based target selection
• The Futility of Exoplanet Biosignatures
• Evolution and Observable Properties of Rocky Planet Atmospheres