Superflare UV flashes impact on Kepler-96 system: a glimpse of habitability when the ozone layer first formed on Earth

TL;DR

This study analyzes superflares on Kepler-96, assessing their potential biological impact on a hypothetical Earth-like planet, highlighting the importance of ozone layers and oceanic protection in early habitability scenarios.

Contribution

It models superflares on Kepler-96 and evaluates their effects on planetary habitability and microbial survival under different atmospheric conditions.

Findings

Superflares with energies up to 1.81×10^{35} ergs were observed.

Ozone layers are crucial for surface microbial survival during superflares.

Microbial life could survive at certain ocean depths despite intense UV radiation.

Abstract

Kepler-96 is an active solar-type star harbouring a Super-Earth planet in close orbit. Its age of 2.3 Gyr is the same as the Sun when there was a considerable increase of oxygen in Earth's atmosphere due to micro-organisms living in the ocean. We present the analysis of superflares seen on the transit lightcurves of Kepler-96b. The model used here simulates the planetary transit in a flaring star. By fitting the observational data with this model, it is possible to infer the physical properties of the flares, such as their duration and the energy released. We found 3 flares within the energy range of superflares, where the biggest superflare observed was found to have an energy of 1.81$\times$10$^{35}$ ergs. The goal is to analyse the biological impact of these superflares on a hypothetical Earth in the habitable zone of Kepler-96 assuming this planet has protection via different scenarios: an Archean and Present-day atmospheres. Also, we compute the attenuation of the flare UV radiation through an Archean ocean. The conclusion is that considering the increase in the UV flux by the strongest superflare emission, {\it E. Coli} and {\it D. Radiodurans} could survive on the surface of the planet only if there was an ozone layer present on the planet atmosphere. However, they could escape from the hazardous UV effects at a depth of 28m and 12m below the ocean surface, respectively. For smaller superflares contribution, {\it D. Radiodurans} could survive in the surface even in an Archean atmosphere with no ozone.