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#^Theia May Have Been Earth’s Early Neighbour, New Study SuggestsScientists have taken a major step toward understanding Theia, the mysterious planet-sized body believed to have struck the young Earth and created the moon. Although this colossal object was destroyed in the impact around 4.5 billion years ago, researchers say its chemical “fingerprints” still linger in Earth and lunar rocks. A
new analysis indicates that Theia likely formed in the same region of the solar system as Earth, making the two worlds early neighbours.
Clues Hidden In Ancient Elements
The research team, led by experts at the Max Planck Institute for Solar System Research and the University of Chicago, gathered exceptionally precise measurements of iron, chromium, molybdenum and zirconium isotopes from terrestrial rocks and from six Apollo-era lunar samples.
These tiny variations in isotopes act like geological timestamps. Because the early solar system didn’t mix its materials evenly, the isotope ratios preserved in rocky bodies can reveal where they originated. As Thorsten Kleine explained, “The composition of a body archives its entire history of formation, including its place of origin.”
Earth and the moon are virtually indistinguishable in these isotope patterns. That strong similarity has been known for years, but until now, it couldn’t reveal whether the moon formed from Theia, from the early Earth itself, or from a blend of both.
Reconstructing A Destroyed Planet
To break the deadlock, the researchers worked backwards by modelling combinations of Earth’s early composition and various possible forms of Theia to see what could have produced the isotopes seen today. They also considered how Earth’s interior evolved before the impact. By the time Theia arrived, Earth had already developed an iron-rich core, leaving some elements, such as iron and molybdenum, scarce in the mantle. Any iron now found in the mantle must have arrived later, likely delivered by the impact.
The results narrowed the possibilities and pointed toward a shared birthplace close to the sun. Lead author Timo Hopp summed up the team’s findings: “The most convincing scenario is that most of the building blocks of Earth and Theia originated in the inner solar system. Earth and Theia are likely to have been neighbours.”
Meteorites Offer The Final Piece
To test their models, the team compared their reconstructed
Theia with known meteorite types, the leftover fragments of early planetary building blocks. Earth’s composition fits well within these familiar categories. Theia’s does not. Its likely mixture includes material unlike any meteorite sampled on Earth, suggesting it formed even closer to the sun than our own planet.
This also explains why Theia’s signature is hard to find today: whatever it was made of, it was extremely rare and may exist nowhere else in the solar system.
A New Picture Of The Moon’s Violent Origin
The findings paint a more intimate picture of the moon-forming collision. Rather than a stranger from the far reaches of the solar system, Theia may have been a near-twin world orbiting alongside Earth before the two finally met in a catastrophic impact that reshaped both bodies forever.
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Theia May Have Been Earth’s Early Neighbour, New Study Suggests appeared first on
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