New constraints on the delivery of cometary water and nitrogen to Earth from the 15N/14N isotopic ratio
arXiv:0906.5221 · doi:10.1016/j.icarus.2009.06.021
Abstract
New independent constraints on the amount of water delivered to Earth by comets are derived using the 15N/14N isotopic ratio, measured to be roughly twice as high in cometary CN and HCN as in the present Earth. Under reasonable assumptions, we find that no more than a few percent of Earth's water can be attributed to comets, in agreement with the constraints derived from D/H. Our results also suggest that a significant part of Earth's atmospheric nitrogen might come from comets. Since the 15N/14N isotopic ratio is not different in Oort-cloud and Kuiper-belt comets, our estimates apply to the contribution of both types of objects.
Accepted for publication in ICARUS