Late Delivery of Nitrogen to the Earth

Atmospheric nitrogen may be a necessary ingredient for the habitability of a planet as its presence helps to prevent water loss from a planet. The present-day nitrogen isotopic ratio, N-15/N-14, in the Earth\u27s atmosphere is a combination of the primitive Earth\u27s ratio and the ratio that might have been delivered in comets and asteroids. Asteroids have a nitrogen isotopic ratio that is close to the Earth\u27s. This indicates either a similar formation environment to the Earth or that the main source of nitrogen was delivery by asteroids. However, according to geological records, the Earth\u27s atmosphere could have been enriched in N-15 during the Archean era. Comets have a higher N-15/N-14 ratio than the current atmosphere of the Earth, and we find that about 5% similar to 10% of nitrogen in the atmosphere of the Earth may have been delivered by comets to explain the current atmosphere of the Earth or the enriched N-15 atmosphere of the Earth. We model the evolution of the radii of the snow lines of molecular nitrogen and ammonia in a protoplanetary disk and find that both have radii that put them farther from the Sun than the main asteroid belt. With an analytic secular resonance model and N-body simulations we find that the v(8) apsidal precession secular resonance with Neptune, which is located in the Kuiper Belt, is a likely origin for the nitrogen-delivering comets that impact the Earth