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Earth's Oceans May Actually Be as Old as Earth Itself

Scientists used to think that Earth was a dead, dry planet for hundreds of millions of years.

They may be  rising, acidifying, and filled with plastics, but we know, definitively, that Earth's oceans do, in fact, exist. The thing is, however, we don't really know when or how they got here. But a new study suggests that they may be as old as Earth itself, which is a totally new hypothesis.

The most popular guesses have been that Earth  probably existed for several hundred million, or even a billion years before water-containing meteorites hit the Earth and gave us liquid oceans.

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But  a paper published today in Science by researchers at the Woods Hole Oceanographic Institution suggests that's not the case.

"The implications are that the migration of water in the inner solar system must have started by eight to 20 years after [the solar system formed], or water was always present in the inner solar system," Horst Marschall and his coauthors wrote. "This evidence moves back the time at which the terrestrial water reservoir is thought to exist."

Now, how the hell do you go about proving when water originally showed up on Earth? By using a bit of chemistry to prove when water showed up on an asteroid.

An illustration of the early solar system. Image: Woods Hole Oceanographic Institution

Marschall and his team investigated the ratio of two separate isotopes of hydrogen on an asteroid known as 4-Vesta, which was formed roughly 14 million years after the solar system formed, according to NASA. (Quick side note: 4-Vesta is one of the asteroid belt's largest hunks of rocks, and is one of the first asteroids to ever be discovered. It was discovered more than 200 years ago. NASA is currently studying Vesta  using a spacecraft known as Dawn)

The ratio of those isotopes, it turns out, is exactly the same as a class of meteorite found on Earth known as carbonaceous chondrites, which contain a lot of water and are believed to be the original source of water in the inner solar system.

Because 4-Vesta is believed to have formed in the same region of the solar system and at the same time as Earth, the thinking is that these giant meteors impacted some body in the inner solar system (perhaps Earth) and put water, or hydrogen at the very least, on various planets, moons, and asteroids as a result of the collision.

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other inner planets could have been wet early and evolved life

"The fact that Earth and Vesta have indistinguishable [hydrogen isotope ratios] suggests that they have the same source of water," Marschall wrote.

What does this mean? It's hard to say, but it does suggest that perhaps Earth wasn't a giant dead rock for much of its early history, as has been previously suggested.  In a statement, Marschall noted that "the planet formed as a wet planet with water on the surface." It also means that our nearby neighbors, which appear pretty dead now, weren't necessarily always that way.

"An implication of that is that life on our planet could have started to begin very early," Sune Nielsen, one of Marschall's coauthors, said in a statement. "Knowing that water came early to the inner solar system also means that the other inner planets could have been wet early and evolved life before they became the harsh environments they are today."

So, next time you hit up the beach, just know that you might be dipping your toes into something that's as old as Earth itself.