Did Earth’s Water Come from Nearby Asteroids?

The origin of Earth’s oceans may have been asteroids from the inner Solar System, suggesting our planet has been a water world from the beginning.

Earth’s water may have been here from soon after the formation of our planet, a new study reveals.

Researchers from the Centre de Recherches Petrographiques et Geochimiques (CRPG) in Nancy, France, determined that a certain type of meteorite may have carried most of the water found in modern oceans.

Enstatite chondrites (EC’s) are composed of material from the inner solar system, and their chemical makeup is nearly identical to the initial composition of the early Earth.

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Earth may have been a water since soon after our planet formed in the early solar system. Image credit: 358611/Pixabay

However, EC’s were thought to be largely dry, having formed in the relatively hot inner solar system. These conditions typically suggested to researchers that Earth’s water would have come from colder bodies, like comets and asteroids, that collided with Earth during the early age of the Solar System.

Laurette Piani from CRPG and her team led examinations of several of these meteorites, revealing these bodies could have delivered up to three times as much water as is found worldwide.

Investigators “measured hydrogen contents and deuterium/hydrogen ratios (D/H) in 13 EC meteorites… They found far more hydrogen than is commonly assumed, with D/H close to that of Earth’s mantle. Combining these data with cosmochemical models, they show that most of Earth’s water could have formed from hydrogen delivered by EC meteorites,” researchers describe in the journal Science.

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Earth’s water may have been delivered by meteorites similar to this 10-cm fragment of one of the EC’s examined in this study. L Piani, Museum of Natural History in Paris

Enstatite chondrites are rare, making up just about two percent of all known meteorites.

“Although thirteen were brought together for this study, some of them had been altered, and only eleven of them were considered to have their original water content,” researchers describe.

They contain similar isotopes (varieties) of oxygen, titanium, and calcium to those found on Earth. This study also revealed hydrogen and nitrogen isotopes in EC’s were similar to those found on our home world.

By studying the isotopes of elements in asteroids, astronomers can determine how and where they formed. Similarities between our world and these bodies suggest the Earth came together from EC’s.

About 95 percent of the water in the world’s oceans matches the isotopic signature of water delivered by chondrites. Just five percent of water on Earth is identical to water from comets.

“I am the shore and the ocean, awaiting myself on both sides.”
― Dejan Stojanovic, The Shape

These objects were thought to be nearly devoid of water. These unexpected findings about EC’s were compelling for researchers.

“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,” Lionel Vacher, a postdoctoral researcher in physics in Arts & Sciences at Washington University in St. Louis, stated.

Using two complimentary techniques, researchers showed EC’s were capable of supplying the Earth with plenty of water to fill our oceans — a few times over.

It would seem our planet was a water world from the beginning.


James Maynard is the founder and publisher of The Cosmic Companion. He is a New England native turned desert rat in Tucson, where he lives with his lovely wife, Nicole, and Max the Cat.

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Writing about space since I was 10, still not Carl Sagan. Weekly video show, podcast, comics, more: www.thecosmiccompanion.net

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