Figure 1: An illustration showing the fate of nitrogen during protoplanetary differentiation.

An undifferentiated protoplanet represents an amalgamation of primitive chondrite-like material. Heat releasing during the decay of ²⁶Al causes large-scale melting which triggers metal-silicate separation as well as volatile degassing^21,22. Vapor-pressure induced solubility sets N abundances in the overlying atmosphere and magma ocean, and consequently the amount of N partitioned into the core via equilibrium exchange between magma ocean-core-atmosphere reservoirs. Post-differentiation, N retained in the silicate and metallic reservoirs only is available during subsequent stages of planetary growth while the proto atmospheres are lost either due to the inability of the smaller bodies to retain their atmospheres or due to impact-induced erosion.