Oxygen isotopic evidence for vigorous mixing during the Moon-forming Giant Impact

TL;DR

This study provides isotopic evidence supporting vigorous mixing during the Moon-forming giant impact, implying a high-energy collision and water-rich impactors, based on oxygen isotope analysis and new planet formation simulations.

Contribution

It introduces a realistic model for oxygen isotopic reservoirs in planet formation simulations, supporting vigorous mixing during the giant impact.

Findings

Earth and Moon have indistinguishable oxygen isotope compositions.

The impact was likely high-energy with high angular momentum.

Late veneer impactors were water-rich, similar to Earth.

Abstract

Earth and Moon are shown here to be composed of oxygen isotope reservoirs that are indistinguishable, with a difference in {\Delta}"17O of -1 +/- 5ppm (2se). Based on these data and our new planet formation simulations that include a realistic model for oxygen isotopic reservoirs, our results favor vigorous mixing during the giant impact and therefore a high-energy high- angular-momentum impact. The results indicate that the late veneer impactors had an average {\Delta}"17O within approximately 1 per mil of the terrestrial value, suggesting that these impactors were water rich.