Assessing the Solar Neutron and Gamma-ray Contribution to Early Earth's Atmospheric Ingredients of Life

Observations of young Sun-like stars suggest that the frequent flares from the young Sun generated high fluence, and high-energy solar energetic particle (SEP) events. This proton irradiation in the early Earth's atmosphere may have produced the crucial building blocks of prebiotic chemistry, as well as greenhouse gases. These protons were likely accelerated at the Sun in superflare-associated coronal mass ejections. As well as charged particles, superflares were likely to have produced secondary high-energy gamma-rays and neutrons. Interactions of solar radiation with the early atmosphere could have resulted in higher abundances of key molecules from which the requisite components for life were formed. Greenhouse gases may have been formed as well, fostering a temperate climate on the early Earth that supported standing bodies of liquid water. Recently, dozens of powerful solar flares have been identified with Fermi/LAT associated with long-duration-gamma-ray-flare emission, high-energy penetrating emission that can last for many hours. Solar neutrons have also been associated with these extreme solar flare events. Both gamma-rays and neutrons could significantly affect the atmospheric chemistry of young Earth-sized exoplanets. Based on modern measurements, we have computed the total integrated intensity and energy of neutrons and gamma-rays expected from extreme events that could contribute to the production of basic life chemistry. These results will be presented together with the discussion of upcoming studies.