We have comets and asteroids to thank for Earth’s water, according to the most widely-held theory among scientists. But it’s not that cut-and-dried. It’s still a bit of a mystery, and a new study suggests that not all of Earth’s water was delivered to our planet that way.
On Earth there is more ocean than land. Of course, there is also a lot of water locked up as ice at the North and South Poles. Where all that water came from is a very good question. Scientists have been wondering about it for a long time. We are still not exactly sure but it is probably a combination of two places.
The Earth has been the blue planet for as many as 3.8 billion years. Ancient sedimentary rock deposits and lava that cooled into characteristic pillow shapes provide irrefutable evidence that liquid water has existed at the Earth’s surface for at least this long. But given how many barren rocks there are in the galaxy, Earth’s abundant oceans raise the question of where all that water came from.