Earth’s building blocks may have had far more water than previously thought

Meteorites suggest that H₂O in the mantle comes from local origins, contrary to expectations

A study of enstatite chondrites (one shown), a type of meteorite similar to the material that formed Earth, suggests that Earth’s primordial building material had plenty of water, even though the planet is thought to have been born in an interplanetary desert.L. PIANI, MUSEUM OF NATURAL HISTORY IN PARIS

A new analysis of meteorites from the inner solar system — home to the four rocky planets — suggests that Earth’s building blocks delivered enough water to account for all the H₂O buried within the planet. What’s more, the water produced by the local primordial building material likely shares a close chemical kinship with Earth’s deep-water reserves, thus strengthening the connection, researchers report in the Aug. 28 Science.

Earth is thought to have been born in an interplanetary desert, too close to the sun for water ice to survive. Many researchers suspect that ocean water got delivered toward the end of Earth’s formation by ice-laden asteroids that wandered in from cooler, more distant regions of the solar system (SN: 5/6/15). But the ocean isn’t the planet’s largest water reservoir. Researchers estimate that Earth’s interior holds several times as much water as is found at the surface.

To test whether or not the material that formed Earth could have delivered this deep water, cosmochemist Laurette Piani of the University of Lorraine in Vandœuvre-lès-Nancy, France, and colleagues analyzed meteorites known as enstatite chondrites. Thanks to many chemical similarities with Earth rocks, these relatively rare meteorites are widely thought to be good analogs of the dust and space rocks from the inner solar system that formed Earth’s building blocks, Piani says.

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Published courtesy of Science News