Student Question

Where did the water on Earth come from?

Expert Answers

An illustration of the letter 'A' in a speech bubbles

There are two different theories that could answer the question of where water on Earth came from.

The first theory is that water was present on Earth when the Earth was formed. This theory is best supported by researchers from the University of Hawaii, who studied rocks on Baffin Island, in Canada, and found glass crystals that contained small droplets of water. Because the rocks came from the mantle, and were untouched by the Earth's crust, researchers believed that the water originated from the formation of Earth itself.

Other researchers believe that surface water would have evaporated and drifted back into space after Earth formed. Instead, these researchers theorize that water was delivered to Earth by way of comets and asteroids. Because ice is a component of both comets and asteroids, collisions with Earth could have caused water formations that resulted in what we now call oceans. Researchers are continuing to analyze water's hydrogen composition to determine if it was more likely to have come from asteroids or comets.

See eNotes Ad-Free

Start your 48-hour free trial to get access to more than 30,000 additional guides and more than 350,000 Homework Help questions answered by our experts.

Get 48 Hours Free Access
Approved by eNotes Editorial