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

TL;DR

This study assesses the habitability of Trappist-1 planets by analyzing UV radiation from stellar flares and its impact on potential surface and oceanic life, considering different atmospheric conditions.

Contribution

It provides the first detailed modeling of UV radiation effects on habitability of Trappist-1 planets during stellar flares, incorporating atmospheric scenarios and biological resilience.

Findings

UV-resistant life could survive on planets f and g surfaces.

Fragile organisms like E. coli could be protected at ocean depths >8m.

Ozone layers would enhance habitability by shielding life from UV radiation.

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.