A new analysis of rocks thought to be at least 2.5 billion years old helps clarify the chemical history of Earth’s mantle — the geologic layer beneath the planet’s crust. The findings hone scientists’ understanding of Earth’s earliest geologic processes, and they provide new evidence in a decades-long scientific debate about the geologic history of Earth. Specifically, the results provide evidence that the oxidation state of the vast majority of Earth’s mantle has remained stable through geologic time and has not undergone major transitions, contrary to what has been suggested previously by other researchers.
