Scientists traced the ancient planet Theia, which vanished billions of years ago, to understand the Moon’s formation.
Astronomers in France, Germany, and the United States analysed terrestrial and lunar rocks to follow Theia’s path.
New research suggests Theia formed much closer to the Sun than previously believed.
Theia collided with early Earth around 4.5 billion years ago, scattering debris that formed the Moon.
Material from Theia became part of both Earth and the Moon after the impact.
The giant impact theory has explained the Moon’s birth since Apollo samples were first studied over 50 years ago.
Theia’s disappearance erased direct chemical evidence, leaving scientists to infer its origin and composition.
Jake Foster from the Royal Observatory Greenwich highlighted that researchers can now almost precisely pinpoint Theia’s source.
He noted that scientists can trace a planet that no longer exists.
Planetary Reverse Engineering
The team examined isotopes in Earth rocks and Apollo lunar samples to uncover chemical signatures.
These isotopes act as fingerprints revealing the environments where rocks originally formed.
Earth and Moon rocks share nearly identical metal isotope ratios, complicating the separation of Theia’s material.
Researchers analysed iron, chromium, zirconium, and molybdenum isotopes to model hundreds of early-Earth and Theia scenarios.
They tested combinations that could reproduce the isotopic patterns observed in present-day samples.
Scientists know that material forming closer to the Sun experiences higher temperatures, producing unique isotope patterns.
By comparing these patterns, researchers determined Theia most likely came from the inner Solar System.
Earlier theories suggested Theia might have formed farther from the Sun than Earth, but new evidence challenges that view.
Implications for Understanding Planetary Formation
Scientists hope this research will illuminate how planets grow, collide, and evolve in young solar systems.
Understanding Theia’s origin helps clarify the conditions that shaped early Earth and the Moon.
The study demonstrates how isotopic analysis can reconstruct lost planetary bodies.
Researchers anticipate using similar methods to trace other ancient Solar System objects.
The findings could refine models of planetary formation, collision, and evolution.
Astronomers aim to expand this research to uncover the history of early Solar System dynamics.
Tracing Theia’s origin offers insight into the processes that governed the first few hundred million years of planetary development.
