Fig. 2: Combined effect of planetesimal evaporation and core formation on the N abundance and N isotope composition of rocky planets.
From: Early planetesimal differentiation and late accretion shaped Earth’s nitrogen budget
a–c The N abundance and (d–f) δ15N in the bulk silicate reservoir as a function of the residual N fraction after evaporation. (a, d) Under relatively reducing conditions; (b, e) Relatively oxidizing conditions. (c, f) The modeled N concentration and δ15N in the bulk silicate part at the oxygen fugacity (log fO2) of Earth’s accreting materials (~IW-3 to IW-1). Earth’s core/mantle mass ratio was also used for models in (a) and (b). The fO2 affects the N partition coefficient between metal and silicate (Dmetal/silicateN) and the N species in silicate melts21,22,24,31,33, which consequently controls the equilibrium N isotope fractionation between vapor (N2) and silicate melt (103lnαN2-silicate) (Fig. 1c). The green areas represent the values of the bulk silicate Earth. The red and blue lines in upper panels represent the initial N concentrations (Cinit) of 500 and 1000 ppm in planetesimals before evaporation, respectively. The dash lines refer to the modeling results at different Dmetal/silicateN values. The yellow, blue, and red shadow regions in the lower panels represent the modeled δ15N in the bulk silicate reservoir with an initial δ15N (δ15Ninit) of +20‰, 0‰, and −20‰, respectively.
