1.5 MAO Ho-Kwang

Deep volatiles as creator and terminator of the living planet

Ho-kwang Mao

Carbon, hydrogen, oxygen, nitrogen and their compounds dictate the emergence, evolution, and extinction of lives in the biosphere. They are regulated by the interactions among the thin layers of atmosphere, hydrosphere, and lithosphere, and in modern ages, impacted by human activities.  Dramatic events in geological history were often attributed to extraterrestrial origins such as asteroid impacts.  However, by far the majority of these volatiles are hidden in the deeper interior; they may have prevailing geochemical influence to all energy and environmental issues, but have not yet been adequately considered.

Recent high P-T experiments revealed fundamentally different chemistry [1, 2] that the iron in deep lower mantle and core can split water and makes the core mantle boundary a colossal hydrogen generator [3, 4] and oxygen reservoir [5].  The perpetual source of hydrogen and its reactions to form ammonia, water, and hydrocarbon provide essential ingredients for life.  The accumulations of oxygen and its outbursts when reaching a saturation point provide an internal sporadic or periodic mechanism for environmental catastrophies throughout the geological history, such as the great oxidation event, mass extinctions, and snowball Earth.

[1] H. Mao et al., National Science Review 4, 870 (2017).

[2] Q. Hu et al., Nature 534, 241 (2016).

[3] S. Zhu et al., J. Am. Chem. Soc. 139, 12129 (2017).

[4] Q. Hu et al., Proc. Natl. Acad, Sci, USA 114, 1498 (2017).

[5] J. Liu et al., Nature 551, 494 (2017).