  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.
