Researchers at The University of New Mexico have published findings in Nature Geoscience indicating that Earth could have generated substantial quantities of water internally during its formation. Rather than relying entirely on external delivery mechanisms such as comets or meteorites, the study proposes that chemical reactions between rocky pebbles and a hydrogen-rich early atmosphere could have produced enormous volumes of water. The research team, led by graduate student Susmita Garai along with professor Zachary Sharp and Peter Olson, conducted high-temperature experiments to test this hypothesis.
Traditional theories about Earth’s water origin have focused on delivery from distant regions of the solar system, with water-rich icy objects traveling inward to contribute to the planet’s supply. However, scientists have faced challenges in fully explaining both the mechanism for transporting sufficient material across such distances and whether this process adequately accounts for Earth’s current chemical composition. The new study explores an alternative pathway in which water forms directly from the interaction of planetary building blocks with atmospheric gases.
During Earth’s earliest formation stages, rocky pebbles accumulated to build the planet through a process called pebble accretion. As the planet grew in mass, it accumulated a dense hydrogen-rich atmosphere with extreme temperatures and pressures. Under these conditions, falling rocky pebbles could have undergone chemical transformation, with hydrogen reacting with iron oxide in silicate rocks to produce metallic iron and release water vapor.
Experimental tests exposed rock samples to temperatures between 1,200 and 1,400 degrees Celsius in the presence of flowing hydrogen gas. Results showed that approximately 80 percent of the iron oxide transformed into metallic iron, with water vapor produced during the reaction. Control experiments using helium instead of hydrogen did not produce the same effect, confirming hydrogen’s essential role. Extrapolating these laboratory results to early Earth conditions suggested the mechanism could have generated hundreds of oceans’ worth of water.
The findings carry broader implications for understanding planetary habitability throughout the universe. If Earth-sized rocky planets forming around other stars develop similarly hot, hydrogen-rich atmospheres during their formation, they too might produce substantial water quantities through comparable chemical processes. This would suggest that water generation is a natural outcome of planet formation rather than a rare occurrence dependent on specific celestial delivery events.
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