Ionizing Radiation in the Martian Atmosphere during Young Sun.

The enhanced magnetic activity of the young sun was an important in the atmospheric evolution and dynamics of the early solar system. Lower solar luminosity associated provided planets a cooler atmospheric and surface environment on the early Earth and Martian surfaces and required production of potent greenhouse gasses in their atmospheres. Within these environments, the dose of ionizing radiation from solar energetic particles (SEPs) from the young Sun could have played an important role in the early phases of planetary habitability. Here, we present a theoretical model of the exposure of the early Mars to high fluence and hard spectra SEPs from the young sun by evaluating the possible magnitude and frequency of solar flares by using possible star spot area, derived from their rotational period. We evaluated annual and maximum flare energy in different cases of sunspot areas for 3 %, 5 % and 10 % of their surfaces. The maximum dose at the Martian top of the atmosphere reaches 5.86 ×10³ Gy (2.65 ×10² Sv) at the time when the sunspot area is ~10 % of the solar surface.