Influence of an Active Young Sun on the Surface Environment of the Hadean Earth

The surface, atmospheric, heliospheric, and oceanic environments of the Hadean Earth (prior to 3.8 Ga) are largely unknown. However, it is thought that life originated during this time, so gaining a better understanding of environmental conditions during this time could help us understand that process [1]. One hypothesis is that life originated in a surface environment and that UV-driven photochemistry supplied the surface with prebiotic reagents [2,3]. Here, we explore a relatively new mechanism for driving unusual atmospheric chemistry space weather. The young Sun was much more magnetically active than today, with more frequent flare events and associated coronal mass ejections [4]. These events introduced large fluences of hard energy solar energetic particles into the Earths neutral atmosphere, resulting in ionization and dissociation of ambient gases [5]. We find that these processes can significantly alter the redox environment of the prebiotic Earth creating large and potentially exploitable energy gradients for early metabolisms, as well as increasing the atmospheric production of prebiotically relevant molecules. This mechanism could have played an important role in the origin of life on Earth and could also be generalized to other rocky (exo)planetary environments. References: [1] Nutman AP, Bennett VC, Friend CRL, Van Kranendonk, MJ, Chivas, AR. 2016. Nature 537: 535-538 [2] Oparin A. 1938. New York: Dover [3] Pinto JP, Gladstone GR, Yung YL. 1980. Science 210(4466) : 183-5. [4] Kay C, Airapetian VS, Luftinger T, Kochukhov O. 2019. ApJ Letters 886 : L37 [5] Airapetian VS, Glocer A, Gronoff G, Hebrard E, Danchi W. 2016. Nature Geo. 9(6) : 452-455.