Late Delivery of Nitrogen to Earth
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, 15N/14N, 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 15N during the Archean era. Comets have higher a 15N/14N ratio than the current atmosphere of the Earth and we find that about 5% ∼ 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 15N 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 ν8 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.
Cheng Cheng, Jeremy L. Smallwood, Rebecca G. Martin, Mario Livio
(Submitted on 17 Dec 2018)
Comments: 14 pages, 7 figures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1812.06956 [astro-ph.EP] (or arXiv:1812.06956v1 [astro-ph.EP] for this version)
Submission history
From: Cheng Chen
[v1] Mon, 17 Dec 2018 18:57:42 UTC (5,472 KB)
https://arxiv.org/abs/1812.06956
Astrobiology
