Photobiological effects at Earth's surface following a 50 pc Supernova

TL;DR

This study models the biological effects of ozone depletion caused by historic nearby supernovae, revealing increased UVB radiation that likely influenced species dynamics without causing mass extinctions.

Contribution

It combines atmospheric chemistry and radiative transfer models to quantify surface UV increases from supernova-induced ozone depletion.

Findings

UVB irradiance increased by 1.1 to 2.8 times, varying by latitude and season.

Biological impacts like DNA damage and skin effects increased, but not to extinction levels.

Species turnover around the Pliocene-Pleistocene boundary may be linked to these effects.

Abstract

We investigated the potential biological impacts at Earth's surface of stratospheric O3 depletion caused by nearby supernovae known to have occurred about 2.5 and 8 million years ago at about 50 pc distance. New and previously published atmospheric chemistry modeling results were combined with radiative transfer modeling to determine changes in surface-level Solar irradiance and biological responses. We find that UVB irradiance is increased by a factor of 1.1 to 2.8, with large variation in latitude, and seasonally at high latitude regions. Changes in UVA and PAR (visible light) are much smaller. DNA damage (in vitro) is increased by factors similar to UVB, while other biological impacts (erythema, skin cancer, cataracts, marine phytoplankton photosynthesis inhibition, and plant damage) are increased by smaller amounts. We conclude that biological impacts due to increased UV irradiance in this SN case are not mass-extinction level, but might be expected to contribute to changes in species abundances; this result fits well with species turnover observed around the Pliocene-Pleistocene boundary.