Where does the water on Earth, one of the few planets in the solar system where water can be found at all, come from? Two scientific theories have been opposing each other on this question for years.
Was there water on Earth from the beginning, even when it was formed, or did it come to Earth only later through 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 origin of the water 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.
Most researchers have tended toward the other hypothesis, based on the high temperatures that prevailed in the solar system 4.5 billion years ago when Earth was formed. These temperatures could have prevented the condensation of water vapour and ice formation.
To solve their problem, the researchers decided to study rocks that are as old as our Blue Planet and have a relatively similar composition. Enstatite chondrites are rare meteorites nowadays and form 2% of the rocks that fell to Earth. They formed 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. Mind you; we are not talking about liquid water in the actual 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.
The Earth had water from the beginning.
The study does not rule out a later water supply from other sources, such as comets. Still, it emphasizes that enstatite chondrites were instrumental in ensuring that the Earth was 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.
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