Surface and oceanic habitability of Trappist-1 planets under the impact of flares

Abstract

The discovery of potentially habitable planets around the ultracool dwarf star Trappist-1 naturally poses the question: could Trappist-1 planets be home to life? These planets orbit very close to the host star and are most susceptible to the UV radiation emitted by the intense and frequent flares of Trappist-1. Here we calculate the UV spectra (100 - 450 nm) of a superflare observed on Trappist-1 with the K2 mission. We couple radiative transfer models to this spectra to estimate the UV surface flux on planets in the habitable zone of Trappist-1 (planets $e$, $f$, and $g$), assuming atmospheric scenarios based on a pre-biotic and an oxygenic atmosphere. We quantify the impact of the UV radiation on living organisms on the surface and on a hypothetical planet ocean. Finally, we find that for non-oxygenic planets, UV resistant lifeforms would survive on the surface of planets f and g. Nevertheless, more fragile organisms (i.e. \textit{E. coli}) could be protected from the hazardous UV effects at ocean depths greater than 8m. If the planets have an ozone layer, any lifeforms studied here would survive in the HZ planets.

13 pages, 6 figures, accepted for publication in Astrobiology

References in corpus (8)

• Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1
• Spectral signatures of photosynthesis II: coevolution with other stars and the atmosphere on extrasolar worlds
• UV Surface Environment of Earth-like Planets Orbiting FGKM Stars Through Geological Evolution
• Temporal evolution of the high-energy irradiation and water content of TRAPPIST-1 exoplanets
• Predicting the Extreme Ultraviolet Radiation Environment of Exoplanets Around Low-Mass Stars: the TRAPPIST-1 System
• Influence of Stellar Flares on the Chemical Composition of Exoplanets and Spectra
• O2- and CO-Rich Atmospheres for Potentially Habitable Environments on TRAPPIST-1 Planets
• Lessons from early Earth: UV surface radiation should not limit the habitability of active M star systems

Cited by in corpus (8)

• No Such Thing as a Simple Flare: Substructure and QPPs Observed in a Statistical Sample of 20 Second Cadence TESS Flares
• Activity of TRAPPIST-1 analogue stars observed with TESS
• Detection of Aerosols at Microbar Pressures in an Exoplanet Atmosphere
• Eta-Earth Revisited II: Deriving a Maximum Number of Earth-like Habitats in the Galactic Disk
• Lower-than-expected flare temperatures for TRAPPIST-1
• Trajectories of Coronal Mass Ejection from Solar-type Stars
• Evaluating Habitability and Biosignature Detection on TOI-700 d: The Role of UV Environment and Atmospheric Pressure
• Biosignature false positives in potentially habitable planets around M dwarfs: the effect of UV radiation from one flare