A groundbreaking study has revealed that a Mars-sized body, known as Theia, originated in the inner Solar System and collided with proto-Earth approximately 4.5 billion years ago. This monumental impact not only transformed both celestial bodies into a molten mass but also resulted in the formation of Earth’s Moon. The research, conducted by scientists from the Max Planck Institute for Solar System Research and the University of Chicago, uncovers new insights into the origins of Theia and its connection to Earth.
Researchers examined samples from Earth, the Moon, and various meteorites to analyze isotopic ratios, which represent different forms of an element. According to Thorsten Kleine, a cosmochemist at MPS, “The composition of a body archives its entire history of formation, including its place of origin.” This analysis indicates that Theia may have existed even closer to the Sun than Earth, possibly sharing a neighborhood with it during the early formation of the Solar System.
The study highlights how different elements and isotopes settled within a cooling planet, influenced by factors such as mass, melting points, and solubilities. For instance, heavier elements like iron and the metal molybdenum sank into proto-Earth’s core, while lighter elements remained in the mantle. This process suggests that much of the iron now found in Earth’s mantle likely arrived after the planet’s reformation, possibly delivered by the impact of a giant celestial body.
To identify the origins of Theia, researchers compared isotopic ratios from various locations in the Solar System. This comparison allowed them to compile an “ingredient list” for Theia, revealing that it shared similarities with materials from the inner Solar System. The isotopic signatures, which resemble “poorly mixed cake batter,” provided a chemical fingerprint for the objects formed from material in that region.
The analysis of meteorites, which serve as cosmic time capsules, proved vital in this research. Non-carbonaceous (NC) meteorites from the inner Solar System differ significantly from carbonaceous chondrites (CC) found in the outer regions. The isotopes associated with Theia displayed ratios that do not match those of Earth’s building blocks, leading the researchers to conclude that both Earth and Theia likely originated from the same region.
Lead author and geoscientist Timo Hopp emphasized, “The most convincing scenario is that most of the building blocks of Earth and Theia originated in the inner Solar System.” This conclusion reinforces the idea that Theia and proto-Earth were, in fact, neighbors in the vast expanse of space.
The collision between these two celestial entities fundamentally altered the course of our planet’s history, resulting in the creation of the Moon, which continues to drift away from Earth at a rate of approximately 1.5 inches (3.8 centimeters) per year.
This significant research is published in the journal Science, contributing to the ongoing exploration of our Solar System’s history and the dynamics of planetary formation. The findings not only enhance our understanding of Earth’s origins but also provide a deeper insight into the complex interactions that shape celestial bodies.
