Scientists have long debated Theia, the vanished planet thought to have formed the Moon.
Astronomers in France, Germany, and the United States analysed lunar and Earth rocks to track Theia.
New research suggests Theia formed much closer to the Sun than previous models predicted.
For over 50 years, the giant impact theory has explained the Moon’s birth.
Theia collided with the early Earth about 4.5 billion years ago, scattering debris.
That debris coalesced into the Moon and mixed with material from both bodies.
Theia disappeared completely, leaving no direct chemical evidence, which complicated studies of its origin.
Astronomers now use rock analysis to reconstruct Theia’s properties and formation region.
Jake Foster of the Royal Observatory Greenwich said researchers can pinpoint the planet’s birthplace despite its disappearance.
Reverse Engineering Planetary Origins
The team studied isotopes in Earth rocks and Apollo lunar samples.
These isotopes act as chemical fingerprints revealing formation conditions.
Earth and Moon rocks share nearly identical metal isotope ratios, complicating separation of Theia’s material.
Researchers examined isotopes of iron, chromium, zirconium, and molybdenum to model possible Earth–Theia scenarios.
They simulated hundreds of collisions to see which combinations match current isotope patterns.
Materials formed closer to the Sun carry distinct isotopic signatures compared with outer Solar System objects.
Comparing patterns, scientists concluded Theia originated in the inner Solar System, nearer the Sun than early Earth.
Previous hypotheses suggested Theia formed farther from the Sun than Earth, but new evidence refutes that.
Implications for Planetary Science
This research helps reconstruct early Solar System dynamics and planetary evolution.
Scientists hope these findings guide studies of how planets grow, collide, and merge.
Understanding Theia’s origin illuminates the Moon’s formation and early Earth conditions.
Researchers believe isotopic analysis can reveal histories of other vanished planetary bodies.
Future missions may provide more samples to refine models of early planetary collisions.
These insights could reshape theories of planetary system formation across the galaxy.
Astronomers expect this approach to improve understanding of planet formation, collisions, and evolution in young solar systems.
