ETH Zurich study suggests Earth formed from inner solar system material

Researchers from ETH Zurich have proposed a new theory regarding the origin of Earth, suggesting the planet may have formed almost exclusively from material within the inner solar system. This finding challenges the long-held hypothesis that a significant portion of Earth’s mass—estimated by some to be between 6% and 40%—arrived from the outer solar system beyond Jupiter.

Led by Paolo Sossi and Dan Bower, the team utilized a statistical approach to analyze isotope ratios across ten different systems found in various meteorites, including samples related to Mars and the asteroid Vesta. Their results indicate that material from the outer solar system likely accounts for less than 2% of Earth’s total mass, and potentially none at all. Sossi noted that the calculations suggest Earth’s building material originates from a single primordial reservoir.

While the study provides a clearer picture of Earth's composition, it raises new questions regarding the planet's water. If Earth did not acquire large amounts of water-rich material from the outer solar system, scientists must still determine how the oceans formed in a region that was significantly hotter during the planet's early development.