How much water was delivered from the asteroid belt to the Earth after its formation?

TL;DR

This study uses n-body simulations to estimate how much water from asteroid impacts could have been delivered to Earth after its formation, suggesting a significant portion of Earth's water may originate from asteroid collisions.

Contribution

It quantifies the impact efficiency of different asteroid regions, especially the $ u_6$ resonance, in delivering water to Earth, providing new insights into Earth's water origin.

Findings

$ u_6$ resonance delivers about 2% of impacting asteroids.

Maximum water delivery could be about eight oceans.

Asteroids in mean motion resonances with Jupiter have negligible impact.

Abstract

The Earth contains between one and ten oceans of water, including water within the mantle, where one ocean is the mass of water on the Earth's surface today. With $n$-body simulations we consider how much water could have been delivered from the asteroid belt to the Earth after its formation. Asteroids are delivered from unstable regions near resonances with the giant planets. We compare the relative impact efficiencies from the $\nu_6$ resonance, the 2:1 mean motion resonance with Jupiter and the outer asteroid belt. The $\nu_6$ resonance provides the largest supply of asteroids to the Earth, with about $2\%$ of asteroids from that region colliding with the Earth. Asteroids located in mean motion resonances with Jupiter and in the outer asteroid belt have negligible Earth-collision probabilities. The maximum number of Earth collisions occurs if the asteroids in the primordial asteroid belt are first moved into the $\nu_6$ resonance location (through asteroid-asteroid interactions or otherwise) before their eccentricity is excited sufficiently for Earth collision. A maximum of about eight oceans of water may be delivered to the Earth. Thus, if the Earth contains ten or more oceans of water, the Earth likely formed with a significant fraction of this water.