This is where the water on Earth comes from: Researchers think they’ve solved the mystery

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Where does the water on Earth, one of the few planets in the solar system where water can be found, come from? For years, two scientific theories have confronted each other on this question.

Was there water on Earth from the beginning, even when it was formed, or did it only come to Earth later due to external influences such as meteorites? A new study could finally end this eternal debate.

The origin of water on Earth
Although all scientists agree that water is the most important element in the origin of life on Earth – which, after all, is 70% water – the water source is disputed.

A new study by the Centre de Recherches pétrographiques et géochimiques in Nancy, France, could end the debate. The study, conducted by French researchers and published in Science in 2020, confirms the hypothesis that water was created when the Earth was formed.

Many researchers tended to the other hypothesis, based on the high temperatures that prevailed in the solar system 4.5 billion years ago when the Earth was formed. These temperatures could have prevented the condensation of water vapour and ice formation.

The crucial role of enstatite chondrites
To solve their problem, the researchers studied rocks as old as our Blue Planet with a similar composition. Enstatite chondrites are rare meteorites, forming 2% of the stones falling to Earth. They started the material from which the Earth and the solar system planets were formed.

In total, the scientists examined a dozen rocks from all over the world, whose composition has hardly been changed by pressure or temperature and whose water content is therefore considered to be “pristine” – i.e. similar to that of the Earth’s primary rocks.

The primary rocks of the Earth
The researchers, therefore, checked the water content. We are not talking about liquid water in the true sense, but rather the molecules involved in its composition, especially hydrogen. The result was clear. Cosmochemist Laurette Piani, who led the research, recounts:

Earth’s primordial rocks would have contained the water equivalent of at least three times the oceans, perhaps much more. We found that the hydrogen isotopic composition of the enstatite chondrites is similar to that of the water stored in the Earth’s mantle.
Another crucial piece of evidence: the isotopic composition of the oceans is 95% consistent with the water from the enstatite chondrites.

Earth had water from the beginning.
The study does not exclude a later water supply from other sources like comets. Still, it emphasizes that enstatite chondrites contributed substantially to the Earth being filled with water from the beginning.

So water was there from the beginning if you believe this study! Even today, “there is ten times more water in the form of hydrogen in the Earth’s mantle than in the oceans,” says Piani.