How is water created on planets? Experiment reveals the creation of water.

Space

Technological Innovation Website Editorial Team - 04/11/2025

By compressing and heating materials analogous to "seeds" of planets, the experiment demonstrated that interactions between the atmosphere of a young planet and its magma ocean generate water and dissolve hydrogen in the molten magma. [Image: Navid Marvi/Carnegie Science]

The birth of water

Science still doesn't know how the water that covers almost our entire planet was formed , so the idea that water arrived on Earth from elsewhere , possibly brought aboard comets and asteroids, has prevailed.

But recent discoveries of water present in protoplanetary disks have rekindled the possibility of local water production on rocky planets , supporting the idea that Earth's water was already here before the planet's birth .

Now, Francesca Miozzi and Anat Shahar, from the Carnegie Institution for Science in the USA, have finally brought these possibilities into the experimental realm.

Previous research, using mathematical modeling and computer simulations, has shown that interactions between atmospheric hydrogen and iron-rich magma oceans during planet formation can produce significant amounts of water.

However, comprehensive experimental testing of this proposed planetary water source had not been carried out until now.

How rocky planets form

Miozzi and Shahar recreated in the laboratory the conditions under which these interactions between hydrogen – representing the primitive planetary atmosphere – and iron-rich silica magma – representing the forming magma ocean – would occur on a young planet.

They did this by compressing samples to nearly 600,000 times atmospheric pressure (60 gigapascals) and heating them to over 4,000 degrees Celsius. These conditions mimic a critical phase in the evolutionary process of rocky planets, which form from the disk of dust and gas surrounding a young star in the period after its birth. The theory is that this protoplanetary disk accumulates material, forming bodies that collide with each other, growing and heating up, until they eventually melt and transform into a vast ocean of magma.

These young planets are often surrounded by a thick layer of molecular hydrogen ( _H2 ) that can act as a "thermal blanket," keeping the magma ocean contained for billions of years before it begins to cool.

"Our work provided the first experimental evidence of two critical processes in early planetary evolution," reported Miozzi. "We showed that a large amount of hydrogen is dissolved in magma and that significant quantities of water are created by the reduction of iron oxide by molecular hydrogen."

Habitability of planets

Taken together, these results experimentally demonstrate that large quantities of hydrogen can be stored in the magma ocean while water formation occurs. This has important implications for the physical and chemical properties of the planet's interior, with potential effects also on core development and atmospheric composition.

"The presence of liquid water is considered crucial for planetary habitability," said Shahar. "This work demonstrates that large quantities of water are created as a natural consequence of planet formation. It represents a major advance in how we think about the search for distant worlds capable of harboring life."

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