Terrestrial effects of moderately nearby supernovae

Abstract

Recent data indicate one or more moderately nearby supernovae in the early Pleistocene, with additional events likely in the Miocene. This has motivated more detailed computations, using new information about the nature of supernovae and the distances of these events to describe in more detail the sorts of effects that are indicated at the Earth. This short communication/review is designed to describe some of these effects so that they may possibly be related to changes in the biota around these times.\n\nSummaryIt has been known for some time that moderately nearby supernovae may have substantial effects on the Earth. Events at {small tilde}150 light years will happen on average every few Myr, but will tend to happen in groups, with long periods between with no events. The effects of cosmic rays from such events appears to be greater than estimated previously. Ozone depletion and the increase of hazardous UVB continues to be important, but new effects come to the fore. Muon irradiation on the ground and hundreds of meters down into the ocean will increase cancer and mutation rates, the differences being most notable in terrestrial megafauna and benthic organisms. Typically larger organisms live long enough to develop cancer; in microorganisms the primary effects would be associated with mutation rates. Atmospheric ionization in the troposphere will greatly increase lightning rates, with a concomitant increase in the rate of wildfires.