DID THE EARTH CREATE ITS OWN OCEANS?

The finding does not prove that all of Earth’s oceans were formed in this way, but it provides experimental evidence for a fascinating possibility: a significant portion of our planet’s water may not have been transported here from space at a later stage. The early Earth itself may have produced it.

The team led by Susmita Garai, from the University of New Mexico, attempted to reproduce in the laboratory what might have occurred during the early stages of a rocky planet's formation.

The story begins with an Earth very different from the one we know today. An extremely hot world, still expanding, surrounded by a hydrogen-rich atmosphere and constantly bombarded by small fragments of rocky material.

The researchers melted completely anhydrous—water-free—mafic rock materials and exposed them to streams of hydrogen. They wanted to see what would happen when these materials came into contact under conditions similar to those proposed for a young planet. And water appeared.

The experiments showed that hydrogen reacted with the iron oxide present in the molten material. The iron was reduced to metal, while the released oxygen combined with the hydrogen. The result of that reaction was H₂O. Water. And it wasn't a negligible amount. The researchers observed a considerable amount being produced in just a few hours of experimentation.

When applied on a planetary scale, the mechanism takes on enormous proportions. During the Earth’s formation, countless rock fragments ranging in size from approximately millimeters to centimeters may have passed through a primitive atmosphere rich in hydrogen. As they heated up and melted during their descent, these materials may have reacted chemically with the atmosphere and produced water vapor. That vapor would eventually become part of the planet’s water supply.

The idea alters a key aspect of one of the classic explanations for our oceans. For decades, there has been debate over how much of Earth’s water arrived from outside the planet, carried by asteroids, planetesimals, and other bodies rich in volatile materials. That possibility is not ruled out by the new study. The results themselves do not establish that all of Earth’s water has a single origin.

What they show is that there is another viable source: the production of water as part of the planet's own formation process.

The experiment also yielded a second interesting result. The metallic iron produced during the reaction captured large amounts of phosphorus and separated it from the silicate material. That metal would subsequently have sunk toward the core.

This could help explain another peculiarity of our planet: the relatively low concentration of phosphorus in Earth's mantle compared to Mars. But the implications may extend far beyond Earth. If this process occurred here, it could also have taken place during the formation of other rocky worlds.

Planets roughly the size of Earth that form through the accumulation of small mineral fragments and initially have hydrogen-rich atmospheres could generate water through the same mechanism.

This means that the formation of oceans may not necessarily require enormous amounts of water to be delivered later from distant regions of a planetary system. Some worlds might produce it as they form.

And that possibility has direct implications for the search for habitable planets outside the Solar System. Liquid water remains one of the key ingredients considered necessary for life as we know it. Understanding how it forms on a planet also means understanding how many worlds might ultimately meet the conditions necessary to support it.

The study has not definitively solved the mystery of the origin of Earth's oceans. But it has just demonstrated something extraordinary in a laboratory: Originally dry materials, a hydrogen-rich atmosphere, and the right conditions can produce water.

Perhaps the oceans that now cover most of our planet were not merely a gift from space. Some of them may have begun to form right here, while the Earth itself was still coming into being.