Creating Earth's Oceans

For decades, the idea that the water in Earth's oceans was delivered by comets has been around. After all, early Earth was a molten, violent, extremely hot place; any water that was here originally would likely have boiled away. Now, a new study suggests that Earth's water did indeed come from comets originating in the Kuiper Belt.

The study compares isotopic ratios in water and deuterium (heavy water) in Earth's water, asteroids, Kuiper Belt comets, and Oort Cloud comets, and determined the ratio in Earth's water most closely fits the ratio in the water ice found in Kuiper Belt objects. The Kuiper Belt is that region of the Solar System from beyond the orbit of Neptune to well past the orbit of Pluto, where many comets orbit, some of which are occasionally jostled onto a flight path that has them swoop into Earth's neighborhood.