Moon’s precursor planet Theia vanished billions of years ago, leaving researchers without direct chemical clues.
Astronomers in France, Germany and the United States analysed ancient lunar and terrestrial rocks to track Theia’s birthplace.
New findings suggest the long-lost planet formed much nearer to the Sun than many earlier theories proposed.
Researchers now believe Theia emerged from the inner Solar System rather than a distant region.
Scientists have long argued that Theia collided with early Earth about 4.5 billion years ago.
Debris from that massive impact created the Moon and scattered Theia’s material across both worlds.
Experts first explored this impact theory over 50 years ago using Apollo mission samples.
Theia’s disappearance left no intact chemical traces, making its composition difficult to pin down.
Researchers continued searching for answers by studying extremely old rocks from Earth and the Moon.
Astronomer Jake Foster said the study paints a clearer picture of ancient Earth and pinpoints Theia’s origins.
He noted that scientists can now estimate the birthplace of a planet that vaporised billions of years ago.
Tracing Ancient Chemical Signatures
The team examined Earth rocks and Apollo lunar samples to study their isotope patterns.
These isotopes act as chemical fingerprints that reveal how and where material formed.
Researchers already knew Earth and Moon rocks share nearly identical metal isotope ratios.
That similarity complicated efforts to distinguish early Earth material from impactor material.
The new study used a planetary reverse-engineering approach to solve this challenge.
Scientists analysed isotopes of iron, chromium, zirconium and molybdenum to build hundreds of models.
Each model tested scenarios that could produce the chemical signatures found today.
Materials nearer the Sun formed under hotter and different conditions than distant materials.
Those variations created distinct isotope patterns across the Solar System.
By comparing these patterns, researchers concluded that Theia formed even closer to the Sun than early Earth.
This finding challenged older theories that placed Theia farther from the Sun than our planet.
A New Window Into Planetary Evolution
Researchers hope this analysis will improve understanding of how planets grow, interact and transform.
Theia’s story may help scientists study early Solar System processes with greater precision.
Future work may reveal how collisions shaped young planets and influenced their long-term development.
The study shows how ancient rocks still hold clues about vanished worlds and primordial events.
