ABEL Model of the Two-step Formation of the Earth and the Significance of ABEL Bombardment to Produce a Habitable Planet

Shigenori MARUYAMA, Toshikazu EBISUZAKI, Yoshinori TANGE
2018 Journal of Geography (Chigaku Zasshi)  
In the recently proposed ABEL model, the Earth was born as a dry planet without atmosphere and ocean components at 4.56 Ga. From 4.37 to 4.20 Ga, bio-elements, such as carbon (C) , hydrogen (H) , oxygen (O) , and nitrogen (N) , were secondarily accreted on the Earth. This twostep formation model of the Earth is referred to as the advent of the bio-elements model (ABEL Model) and the event of the advent of bio-elements (water component) is referred to as ABEL Bombardment. It is evident that the
more » ... s evident that the solid Earth originated from enstatite chondrite-like dry material because of its oxygen isotopic composition and similar isotopes. On the other hand, the Earth's water originated primarily from carbonaceous chondrite material based on the hydrogen isotopic ratio. The ABEL model successfully explains this enigma between solid Earth and water. In addition, the importance of the secondary accretion of oxidizing bio-elements should be emphasized because this event became a precursor to initiating the metabolism for life to emerge on a highly reductive planet. If ABEL Bombardment had not occurred, life would never have emerged on the Earth. Therefore, ABEL Bombardment was one of the most important events for this planet to evolve into a habitable planet. Moreover, ABEL Bombardment is thought to be the trigger to switch from stagnant lid tectonics to plate tectonics on this planet because of the injection of volatiles into the initial dry Earth. Key words: origin of the Earth, formation of the Earth, origin of terrestrial water, planetary formation theory, origin of life :地球の起源,地球の誕生,地球の水の起源,地球形成モデル,生命の起源 * 東京工業大学地球生命研究所 ** ノボシビルスク大学 *** 理研 **** 高輝度光科学研究センター
doi:10.5026/jgeography.127.647 fatcat:vq4dfocuy5ckve7tm2epgl5cvi