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