Figure 6: Effect of rate of protoplanetary accretion versus differentiation on the nitrogen budget of large Earth-like planets.

If the rate of differentiation was greater than rate of accretion, then differentiated asteroid-sized bodies would be the primary building blocks for subsequent stages of growth of larger planets like Earth. In such cases (scenarios 1-7), N budget of the BSE cannot be satisfied during the main stage of planetary growth because the mantles and cores of differentiated asteroids were extremely N-poor. However, if the rate of accretion was greater than rate of differentiation, then N budget of the BSE can be set during the main growth period of Earth via primitive rocky bodies which grew to planetary-embryo-size before undergoing differentiation (scenarios 8-10). The highest value of accreted N (2000 ppm) in a) represents the average N content of volatile-rich CI chondrites⁵. N abundance in magma ocean + atmosphere in a) is calculated in terms of the present-day atmospheric nitrogen (PAN) inventory. Right axis label in a) represents end-member growth scenarios of Earth via collisional growth. For example, growth scenario 1 represents Vesta-sized differentiated bodies (0.04 R_⊕; 0.00004 M_⊕),) accreting together to form an Earth-sized planet and growth scenario 2 represents Vesta-sized differentiated bodies (0.04 R_⊕) initially accreting to form intermediate-sized rocky bodies (0.12 R_⊕; 0.001 M_⊕),) which subsequently accrete to form an Earth-sized planet. Grey shaded region represents the estimated N content of the present-day BSE^1,40.