While the theory that the Earth’s oceans have extraterrestrial origins is the dominant explanation for the origin of water on Earth, a new theory has arisen to challenge this assumption.
The previous theory took note of the fact that, while water was abundant in our solar system — see Saturn’s Enceladus or Jupiter’s Europa — it was primarily found in the Outer Planets, while Mercury, Venus, and Mars are dry (at least, currently). What happened, so the theory goes, is that rocks, meteors, and other such spaceborne objects had crashed into these planets, releasing water onto them for a period of millions of years, according to Forbes.
The other theory is that Earth’s water is native: during the formation of the Inner Planets, the inward crush of the metals and stones that make up these planets had essentially “squeezed” all the water out of their insides and onto the surface.
What happened, so the theory goes, is that rocks, meteors, and other such spaceborne objects had crashed into these planets, releasing water onto them for a period of millions of years
Lynda Hallis, of Glasgow University in the UK, has come up with new evidence to support this latter theory, using the D/H (Deuterium to Hydrogen) levels of the water found on Earth. While much of Earth’s water is a match for the D/H levels found in space, Hallis and her team wanted to test something deeper down, and to get a better idea of what the water would have been like so many years go, reported The Weather Channel.
Using some of the oldest rocks available on this planet, Hallis was quoted as saying “on their way to the surface, these rocks were never affected by sedimentary input… [and] their source region has remained untouched since Earth’s formation. Essentially … the water they contain gives us an invaluable insight into Earth’s early history and where it’s water came from.”
The D/H levels in the water samples found in these rocks was more similar to Earth’s than to space objects, which suggests water came from the Earth.
There is still a great deal of controversy over which theory is correct.