Astronomers studied ancient lunar and terrestrial rocks to trace the origin of the vanished planet Theia.
They suggest Theia, which helped form the Moon, may have formed much closer to the Sun than thought.
Scientists believe Theia collided with early Earth about 4.5 billion years ago, creating debris that became the Moon.
The giant impact theory has guided understanding of the Moon’s formation since Apollo samples arrived over fifty years ago.
Theia disappeared billions of years ago, leaving no direct chemical evidence and obscuring its composition and origin.
Researchers in France, Germany, and the United States now reconstruct Theia’s history using isotopic analysis.
Jake Foster of the Royal Observatory Greenwich called the study exciting, noting it pinpoints Theia’s birthplace with precision.
He explained that researchers can trace a planet that vanished 4.5 billion years ago using chemical fingerprints.
Reverse Engineering a Lost Planet
The team examined iron, chromium, zirconium, and molybdenum isotopes in Earth and Moon rocks to reveal early Solar System conditions.
These isotopes act as chemical fingerprints, showing where materials originally formed.
Earth and Moon rocks share nearly identical isotope ratios, complicating the separation of Theia’s remnants from early Earth material.
Researchers modelled hundreds of scenarios combining Earth and Theia materials to match observed isotopic signatures.
Scientists know that materials closer to the Sun formed under different temperatures than those farther out, leaving distinct isotopic patterns.
Comparing these patterns revealed that Theia likely formed in the inner Solar System, closer to the Sun than early Earth.
Some earlier theories suggested Theia formed farther from the Sun, but this study challenges that view.
Implications for Planetary Science
Researchers hope this approach improves understanding of how planets form, collide, and evolve in early solar systems.
The findings could help scientists model planetary growth and destruction across the inner Solar System.
This analysis demonstrates how ancient rocks preserve clues about long-vanished worlds.
Scientists expect future studies to use similar methods to trace other planetary bodies.
By revealing Theia’s origin, researchers gain insight into the processes that shaped both Earth and the Moon.
The study highlights how isotopic fingerprints can reconstruct planetary history with remarkable detail.
Researchers aim to expand this method to study planetary evolution in other star systems.
