Radiation strikes

No known terrestrial process – prior to the Nuclear Age - could have caused such sharp enrichments in the atmospheric activity of radiocarbon. Thus, the spikes must have been instigated by bursts of radiation from space.

At first, exploding stars (supernovae), or even Black Holes, were proposed as possible sources, as the sun was not thought capable of emitting radiation of the necessary magnitude. However, many now believe the impacts were caused by extreme solar emissions known as superflares.