Our Galaxy is filled with high-energy subatomic particles generated by exploding stars or supernovae, also known as cosmic rays. These particles strike the Earth’s atmosphere and produce more (secondary) particles, which damages the ozone layer and causes DNA damage to terrestrial and marine life.
In Carl Sagan’s words: ” The evolution of life is driven in parts through mutations by the deaths of distant stars. We are, in a very deep sense tied to the cosmos.”
Life has evolved over the past ~ 3 billion years in presence of this radiation, which itself has varied considerably during the period. As demonstrated by the Miller-Urey experiment, lightning plays a very important role in the formation of complex organic molecules, which are the building blocks of more complex structures forming life. There is growing evidence of an increase in the lightning rate with increasing flux of charged particles. Is there a connection between this enhanced rate of cosmic rays and the origin of life? Cosmic ray secondaries are also known to damage DNA and cause mutations, leading to cancer and other diseases. It is now possible to compute radiation doses from secondary particles, in particular muons and neutrons. Have the variations in cosmic ray flux affected the evolution of life on earth?
I have recently written a paper about this with Adrian Melott, where we describe the mechanisms of cosmic rays affecting terrestrial life and review the potential implications of the variation of high-energy astrophysical radiation on the history of life on earth. If anyone is interested in reading further, here is a link with more details:
Here is Carl Sagan’s video explaining it: http://youtu.be/MvHHZO2wmmg?t=1m30s