Planetary scientists have long believed that Earth formed from planetary objects similar to meteorites. Then, a decade ago, perplexing new measurements challenged that assumption by showing that Earth and its supposed “building blocks” actually contain significantly different isotopic compositions.

For the past 10 years, scientists have been trying to understand why. Recent work by the University of Chicago’s Christoph Burkhardt (now at the University of Muenster in Germany) and Nicolas Dauphas, together with their collaborators from Lawrence Livermore National Laboratory and the University of Münster, suggest a new explanation that may help illuminate both the composition of Earth and the beginnings of the solar system itself.

“These recent measurements contribute to the growing evidence that the meteorites delivered to Earth provide an imperfect match to Earth’s composition,” said Richard Carlson, director of the Department of Terrestrial Magnetism at the Carnegie Institution for Science. Carlson was one of the scientists who found the compositional mismatch between meteorites and Earth 10 years ago. “This realization opens new views both to how Earth formed and to the bulk chemical composition of our home planet.”

The study will be published in the Sept. 15, 2016, issue ofNature.