Cosmic rays and terrestrial life: A brief review

Atri, D. & Melott, A.

Astroparticle Physics, 53, pp 186-190.

doi:10.1016/j.astropartphys.2013.03.001, 2014.

[arXiv] [Materia]

Listen to the author interview! [mp3 download]

Brief summary

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 particles, which damages the ozone layer and causes DNA damage to terrestrial and marine life. We have presented a brief account of both periodic and non-periodic sources of cosmic ray variations over long timescales and their effects on terrestrial life.

[Discussion on SAGANet]

Extended summary

High-energy radiation bursts are commonplace in our Universe. From nearby solar flares to distant gamma ray bursts, a variety of physical processes accelerate charged particles to a wide range of energies, which subsequently reach the Earth. Such particles contribute to a number of physical processes occurring in the Earth system. A large fraction of the energy of charged particles gets deposited in the atmosphere, ionizing the atmosphere, causing changes in its chemistry and affecting the global electric circuit. Remaining secondary particles contribute to the background dose of cosmic rays on the surface and parts of the subsurface region.

Life has evolved over the past ~ 3 billion years in presence of this background 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 increase in the lightning rate with increasing flux of charged particles. Is there a connection between 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? 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.