http://arxiv.org/abs/2105.05313
The effect of protoplanetary differentiation on the fate of life essential volatiles like nitrogen and carbon and its subsequent effect on the dynamics of planetary growth is unknown. Because the dissolution of nitrogen in magma oceans depends on its partial pressure and oxygen fugacity, it is an ideal proxy to track volatile redistribution in protoplanets as a function of their sizes and growth zones. Using high pressure and high temperature experiments in graphite undersaturated conditions, here we show that the iron loving character of nitrogen is an order of magnitude higher than previous estimates across a wide range of oxygen fugacity. The experimental data combined with metal, silicate and atmosphere fractionation models suggest that asteroid sized protoplanets, and planetary embryos that grew from them, were nitrogen depleted. However, protoplanets that grew to planetary embryo size before undergoing differentiation had nitrogen rich cores and nitrogen poor silicate reservoirs. Bulk silicate reservoirs of large Earth like planets attained nitrogen from the cores of latter type of planetary embryos. Therefore, to satisfy the volatile budgets of Earth like planets during the main stage of their growth, the timescales of planetary embryo accretion had to be shorter than their differentiation timescales, that is, Moon to Mars sized planetary embryos grew rapidly within 1 to 2 million years of the Solar System formation.
D. Grewal, R. Dasgupta, T. Hough, et. al.
Thu, 13 May 21
33/60
Comments: 44 pages, 6 figures, 9 extended data figures. Nat. Geosci. (2021)