The Earth is three-fourths water, with more than 70% of its surface is covered with water essential for life to survive. But how did Earth had its water? The answer to that has been a longstanding scientific debate by scientists for many decades now.
On Thursday, August 27, a team of French researchers published their study in the journal Science which reveals which space rocks were responsible for bringing water on Earth, contradicting the existing meteorite theory.
Doubts on Meteorites Theory
Lead researcher and cosmochemist Laurette Piani said that the results of their study contradict the existing meteorite theory, which explains the once-dry planet received its water from the far-reaching comets and asteroids.
According to theories on the formation of the Solar System, the Sun was surrounded by large disks of gas and dust that became the planets nearest to it later on. However, their temperatures were too hot to sustain ice, which would explain the barren conditions of Mercury, Venus, and Mars.
Only Earth has vast oceans, a humid atmosphere, and is well-hydrated. Therefore in the meteorite theory, scientists believe that water came after caused by meteorites known as carbonaceous chondrites that are rich in hydrous minerals.
However, the Earth's rocks do not match with the chemical composition of these meteorites that can also be formed in the outer Solar System, making it less likely that they have showered the early Earth.
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The Earth and Other Inner Planets' Building Blocks
Scientists have discovered another type of meteorite that matches closely with the chemical composition of the rocks on the planet, called the enstatite chondrites.
These meteorites contain the same isotopes of oxygen, titanium, and oxygen, which indicates that they were the building blocks of Earth and the other inner planets.
But because they are formed too close from the Sun, scientists thought they are too dry to have caused the water on the rich reservoirs of water on Earth.
Piani and her colleagues from Centre de Recherches Petrographiques et Geochimiques became intrigued about these meteorites and tested whether this assumption was true or not.
They used mass spectrometry, a technique that measures the hydrogen content in 13 enstatite chondrites wherein they found enough hydrogen to provide Earth with at least three times or possibly more the water mass in the oceans.
These types of meteorites have now become rare, with only 2% of known meteorites in collections. They have become hard to find in pristine and uncontaminated condition.
Moreover, the researchers also discovered two isotopes of hydrogen similar to the water stored in the terrestrial mantle when comparing it to a DNA match.
Piani said that the oceans' isotopic composition matched with a mixture containing 95% of enstatite chrondite's water. This proves further that they were responsible for much of the Earth's water.
Furthermore, the authors found nitrogen isotopes from the meteorites that are also similar to Earth's nitrogen. They propose that these rocks could have also been the source of the most abundant compound in the atmosphere.
In addition, Piani said that they do not discount the addition of water by later comets or other sources. Instead, their research aims to inform that enstatite chondrites had a significant contribution to Earth's water budget when it first formed.
NASA's planetary scientist, Anne Peslier, said that the new study had brought a very important and elegant element to the origins of water on Earth, a puzzle that has a longstanding debate in the scientific community.
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