A recent study published in the journal Science by researchers from the Max Planck Institute for Solar System Research and the University of Chicago suggests that the celestial body known as Theia was not only a significant impactor in Earth’s history but also a neighboring entity within the solar system. This impact, which occurred approximately 4.5 billion years ago, led to the formation of the moon and transformed the trajectory of Earth’s development.
The research aims to uncover the characteristics of Theia, a body that was completely destroyed during its collision with the young Earth. Understanding its size, composition, and origin has been a challenge, but scientists are now analyzing evidence found in the isotopic compositions of terrestrial and lunar rocks. According to Thorsten Kleine, Director at MPS and co-author of the study, “The composition of a body archives its entire history of formation, including its place of origin.”
The research team meticulously examined the ratios of various isotopes of iron, chromium, molybdenum, and zirconium in samples from Earth and the moon. They analyzed 15 terrestrial rocks and six lunar samples collected during the Apollo missions. Their findings indicate that Earth and the moon share a striking similarity in their isotopic compositions, suggesting that both bodies may have originated from similar materials.
Despite these similarities, the study highlights the complexity of determining Theia’s exact nature. The models propose several collision scenarios, with most suggesting that the moon formed primarily from Theia’s material. Yet, there remains the possibility that the moon consists largely of material from early Earth’s mantle, or that the two bodies mixed incompletely during the collision.
Reverse Engineering Planetary Formation
To gain insights into Theia, the researchers employed a reverse engineering approach. By analyzing the isotopic data from Earth and lunar rocks, they simulated various scenarios that could explain the current isotopic ratios. This involved exploring different compositions and sizes of Theia and early Earth.
The analysis revealed that elements such as iron and molybdenum had settled into Earth’s core during its formation, suggesting that any iron found in the mantle today likely came from Theia. Other elements, such as zirconium, remained in the mantle, providing a more complete picture of the planet’s early development.
The team concluded that the most plausible scenario is that the building blocks of both Earth and Theia originated from the inner solar system. Timo Hopp, the lead author of the study, noted, “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 neighbors.”
The Implications of Theia’s Composition
While the isotopic composition of early Earth can be primarily represented by known meteorite classes, Theia’s composition remains less clear. Different classes of meteorites originate from various regions of the solar system, serving as a reference for the materials available during the formation of Earth and Theia. The research suggests that Theia may have included previously unidentified materials from regions closer to the sun than Earth.
This study enhances our understanding of planetary formation and the history of our solar system. By piecing together the isotopic evidence, researchers are uncovering the narrative of how celestial bodies like Earth and Theia interacted in their formative years. The findings provide a deeper insight into the processes that shaped our planet and its constant companion, the moon.
For further information, the study can be accessed in the journal Science under the title “The Moon-forming impactor Theia originated from the inner Solar System” by Timo Hopp et al.
