# Late Delivery of Nitrogen to Earth

## TL;DR

This paper investigates the late delivery of nitrogen to Earth, suggesting comets from the Kuiper belt, influenced by secular resonance, contributed significantly to Earth's atmospheric nitrogen, impacting its habitability.

## Contribution

It models nitrogen snow line evolution and identifies Kuiper belt comets, affected by secular resonance, as key nitrogen sources for Earth, providing new insights into planetary nitrogen delivery.

## Key findings

- Comets contributed about 5-10% of Earth's atmospheric nitrogen.
- Nitrogen snow lines are located beyond the asteroid belt.
- Secular resonance with Neptune influences comet delivery to Earth.

## Abstract

Atmospheric nitrogen may be a necessary ingredient for the habitability of a planet since its presence helps to prevent water loss from a planet. The present day nitrogen isotopic ratio, $^{15}$N/$^{14}$N, in the Earth's atmosphere is a combination of the primitive Earth's 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's. 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's atmosphere could have been enriched in $^{15}$N during the Archean era. Comets have higher a $^{15}$N/$^{14}$N ratio than the current atmosphere of the Earth and we find that about $5\%$ $\sim$ $10\%$ of nitrogen in the atmosphere of the Earth may have been delivered by comets to explain the current Earth's atmosphere or the enriched $^{15}$N Earth's atmosphere. 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 $\nu_8$ 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.