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08-27-2020

Earth may have had water from the time it formed

The results of a new study from Washington University indicate that Earth was always wet and did not need distant comets or asteroids to deliver the elements necessary for water to appear. The research suggests that water came from materials that were available in the solar system when our planet formed.

An international team of  researchers discovered that a type of meteorite called an enstatite chondrite contains enough hydrogen to deliver at least three times the amount of water held in Earth’s oceans.

Enstatite chondrites are composed of material from the inner solar system, which is essentially the same material that Earth was formed from.

“Our discovery shows that the Earth’s building blocks might have significantly contributed to the Earth’s water,” said study lead author Laurette Piani. “Hydrogen-bearing material was present in the inner solar system at the time of the rocky planet formation, even though the temperatures were too high for water to condense.”

While it was too hot for water to condense when the building blocks of Earth came together, the meteorites indicate that water did not come from a distant source.

“The most interesting part of the discovery for me is that enstatite chondrites, which were believed to be almost ‘dry,’ contain an unexpectedly high abundance of water,” said study co-author Lionel Vacher, who prepared some of the enstatite chondrites in this study for water analysis while completing his PhD at Universite de Lorraine. 

At Washington University, Vacher is working on understanding the composition of water in various types of meteorites. 

Enstatite chondrites are rare, but their isotopic similarity to Earth make them particularly interesting to scientists. These meteorites have similar oxygen, titanium, and calcium isotopes as Earth, and the current reveals that their hydrogen and nitrogen isotopes are also similar. 

“If enstatite chondrites were effectively the building blocks of our planet — as strongly suggested by their similar isotopic compositions — this result implies that these types of chondrites supplied enough water to Earth to explain the origin of Earth’s water, which is amazing!” said Vacher.

“Only a few pristine enstatite chondrites exist: ones that were not altered on their asteroid nor on Earth,” said Piani. “In our study we have carefully selected the enstatite chondrite meteorites and applied a special analytical procedure to avoid being biased by the input of terrestrial water.”

“It was commonly assumed that these chondrites formed close to the sun. Enstatite chondrites were thus commonly considered ‘dry,’ and this frequently reasserted assumption has probably prevented any exhaustive analyses to be done for hydrogen.”

The study is published in the journal Science.

By Chrissy Sexton, Earth.com Staff Writer

 

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