A recent study by researchers from the University of Göttingen and the Max Planck Institute for Solar System Research has revealed exciting insights into how the moon formed and where Earth’s water came from.
Their findings challenge some long-held theories about our planet and its closest neighbor.
For years, scientists believed the moon formed after a massive collision between early Earth and a Mars-sized protoplanet called Theia.
This collision supposedly mixed materials from both bodies, forming the moon.
However, new research suggests the moon might have formed mostly from material ejected from Earth’s mantle, with only a small contribution from Theia.
The researchers analyzed oxygen isotopes—different forms of the oxygen element—from 14 lunar samples and Earth minerals. They used a laser technique to measure the isotopes, focusing on oxygen-17 (17O).
Their findings showed a striking similarity between Earth and moon samples, which suggests the moon was primarily made from Earth’s mantle material.
“One explanation is that Theia, before colliding with Earth, lost much of its rocky mantle in earlier impacts and hit Earth like a metallic cannonball,” explains Professor Andreas Pack from Göttingen University.
“This would mean Theia’s material became part of Earth’s core, and the moon formed from Earth’s mantle.”
This explanation resolves a long-standing problem in planetary science called the “isotope crisis,” where scientists couldn’t explain why Earth and moon materials were so similar.
The study also offers clues about the origin of water on Earth. Many scientists thought water arrived much later, after the moon formed, through impacts from asteroids or comets during an event known as the Late Veneer.
Since Earth was hit by more of these objects than the moon, their theory suggested Earth and moon rocks should show differences in their isotopes.
However, the new data shows no such difference, ruling out many types of meteorites as sources of Earth’s water. Instead, the researchers propose that a specific class of meteorites called enstatite chondrites may have delivered water to Earth. These meteorites are isotopically similar to Earth and contain enough water to explain all the water we have today.
This study, published in the Proceedings of the National Academy of Sciences, helps us better understand the moon’s origin and the history of water on Earth.
Knowing more about these ancient events not only deepens our knowledge of Earth’s past but also provides clues about how planets and their moons form in other parts of the universe.
