Supernova Triggers for End-Devonian Extinctions

• Published in: arXiv.org 2020-08
• Main Authors: Fields, Brian D, Melott, Adrian L, Ellis, John, Ertel, Adrienne F, Fry, Brian J, Lieberman, Bruce S, Liu, Zhenghai, Miller, Jesse A, Thomas, Brian C
• Format: Article
• Language: English
• Subjects: Biodiversity; Cosmic rays; Explosions; Galactic disk; Gamma rays; Ionizing radiation; Mass extinctions; Massive stars; Ozone; Radiation damage; Radioisotopes; Speciation; Supernovae
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2007.01887

The Late Devonian was a protracted period of low speciation resulting in biodiversity decline, culminating in extinction events near the Devonian-Carboniferous boundary. Recent evidence indicates that the final extinction event may have coincided with a dramatic drop in stratospheric ozone, possibly due to a global temperature rise. Here we study an alternative possible cause for the postulated ozone drop: a nearby supernova explosion that could inflict damage by accelerating cosmic rays that can deliver ionizing radiation for up to \(\sim 100\) kyr. We therefore propose that the end-Devonian extinctions were triggered by supernova explosions at \(\sim 20\) pc, somewhat beyond the "kill distance" that would have precipitated a full mass extinction. Such nearby supernovae are likely due to core-collapses of massive stars; these are concentrated in the thin Galactic disk where the Sun resides. Detecting either of the long-lived radioisotopes Sm-146 or Pu-244 in one or more end-Devonian extinction strata would confirm a supernova origin, point to the core-collapse explosion of a massive star, and probe supernova nucleosythesis. Other possible tests of the supernova hypothesis are discussed.