Mass Extinction

One of the prevailing theories for the cause of the Ordovician–Silurian mass extinction is a gamma-ray burst that struck the planet 450 million years ago and killed almost all life on Earth. Researchers speculate that a gamma-ray burst originated from a hypernova within 6,000 light-years of Earth. A 10-second burst would have stripped the Earth's atmosphere of half of its ozone almost immediately, exposing all life on earth to high levels of extreme ultraviolet radiation. Nearly 85% of marine species were wiped out.