The impact of Ozone on Earth-like exoplanet climate dynamics: the case of Proxima Centauri b

Abstract: The emergence of the James Webb Space Telescope and the development of other advanced observatories (e.g., ELTs, LIFE and HWO) marks a pivotal moment in the quest to characterize the atmospheres of Earth-like exoplanets. Motivated by these advancements, we conduct theoretical explorations of exoplanetary atmospheres, focusing on refining our understanding of planetary climate and habitability. Our study investigates the impact of ozone on the atmosphere of Proxima Centauri b in a synchronous orbit, utilizing coupled climate chemistry model simulations and dynamical systems theory. The latter quantifies compound dynamical metrics in phase space through the inverse of co-persistence ($\theta$) and co-dimension (d), of which low values correspond to stable atmospheric states. Initially, we scrutinized the influence of ozone on temperature and wind speed. Including interactive ozone (i.e., coupled atmospheric (photo)chemistry) reduces the hemispheric difference in temperature from 68 K to 64 K, increases ($\sim+$7 K) atmospheric temperature at an altitude range of $\sim$20-50 km, and increases variability in the compound dynamics of temperature and wind speed. Moreover, with interactive ozone, wind speed during highly temporally stable states is weaker than for unstable ones, and ozone transport to the nightside gyres during unstable states is enhanced compared to stable ones ($\sim+$800 DU). We conclude that including interactive ozone significantly influences Earth-like exoplanets' chemistry and climate dynamics. This study establishes a novel pathway for comprehending the influence of photochemical species on the climate dynamics of potentially habitable Earth-like exoplanets. We envisage an extension of this framework to other exoplanets.

• The paper demonstrates that incorporating interactive ozone narrows the hemispheric temperature difference from 68 K to 64 K and raises stratospheric temperatures by about 7 K.
• It employs a 3D climate-chemistry model and dynamical systems theory to quantify changes in wind speeds and atmospheric stability, including an ~800 DU increase in ozone transport to nightside gyres.
• The findings highlight ozone’s critical role in exoplanet habitability, offering a framework for future observational studies with telescopes like JWST and upcoming missions.

The Impact of Ozone on Earth-like Exoplanet Climate Dynamics: A Study of Proxima Centauri b

The study under discussion explores the effect of ozone on the atmospheric dynamics of Proxima Centauri b, a tidally locked exoplanet orbiting an M-dwarf star in close proximity to our solar system. The investigation employs a three-dimensional coupled climate-chemistry model (CCM) to simulate the climate and habitability of this exoplanet, emphasizing the role of interactive ozone.

Key Findings

The primary focus of the research is to evaluate the influence of ozone on various atmospheric variables, including temperature and wind speed, using a sophisticated climate model. Importantly, incorporating interactive ozone in the model results in significant changes to the exoplanet's climate dynamics, most notably a reduction in hemispheric temperature difference from 68 °K to 64 °K and an average stratospheric temperature increase of approximately 7 °K within an altitude range of 20-50 km. Moreover, the study highlights that interactive ozone plays a pivotal role in modulating wind speeds and atmospheric stability, with significant increases in ozone transport to nightside gyres during unstable conditions (~+800 DU).

The study also employs dynamical systems theory to calculate compound metrics such as the inverse of local co-persistence (θ) and local co-dimension (d), which serve as measures of atmospheric stability, with lower values indicating stable atmospheric states. These metrics demonstrate enhanced variability and altered dynamics in the presence of interactive ozone.

Implications and Future Directions

The findings suggest that ozone, though often considered a minor component, significantly impacts the climate and atmospheric dynamics of habitable zone exoplanets. The research provides a framework for understanding climate-chemistry interactions that could extend to other exoplanets, with practical implications for interpreting observational data from the James Webb Space Telescope and future observatories like LIFE and the Habitable Worlds Observatory.

The study raises important questions regarding how variations in stellar type and the FUV/NUV flux ratio impact ozone formation and vertical distribution, thereby influencing exoplanet habitability. Future research could explore these interactions further, including the variability of initial O₂ abundances and their implications for climate models.

Overall, this research represents a crucial step toward understanding the role of photochemically active species like ozone in shaping exoplanet atmospheres, influencing their potential habitability and guiding future observational and theoretical work in planetary science.