In a groundbreaking study, researchers from MIT have reportedly uncovered remnants of materials from the ancient proto Earth, a primitive version of our planet that existed over four billion years ago. This discovery provides a tangible link to an era long thought to be lost following a catastrophic collision that reshaped Earth”s early history.
The proto Earth, characterized by its molten surface and intense volcanic activity, was drastically transformed when a Mars-sized object collided with it less than 100 million years after its formation. This impact not only led to the creation of the Moon but also permanently altered the planet”s composition, erasing all traces of the proto Earth.
However, a new study published in the journal Nature Geosciences suggests that some remnants of the proto Earth may have been preserved. Co-lead author Nicole Nie, an assistant professor of earth and planetary sciences at MIT, stated, “This is maybe the first direct evidence that we”ve preserved the proto Earth materials. We see a piece of the very ancient Earth, even before the giant impact. This is amazing because we would expect this very early signature to be slowly erased through Earth”s evolution.”
The researchers based their findings on a unique chemical “anomaly” found in samples of ancient rocks. The key to this discovery lay not underground but in meteorites. Starting in 2023, Nie”s team analyzed the chemical compositions of various meteorites from around the world, which serve as time capsules reflecting different stages of the solar system”s 4.6 billion-year history.
When comparing the meteorite samples to those from Earth, the team identified a “potassium isotopic anomaly,” indicating an unusual ratio of potassium isotopes. On modern Earth, potassium-39 and potassium-41 are the dominant isotopes, while potassium-40 exists in a negligible amount. In contrast, the meteorites revealed a potassium isotope balance that differed from Earth”s, suggesting that the rocks with this imbalance predated the current composition of our planet.
Nie explained, “In that work, we found that different meteorites have different potassium isotopic signatures, and that means potassium can be used as a tracer of Earth”s building blocks.” With this insight, the researchers examined some of the oldest known rock samples, seeking this specific potassium signature, and found compelling evidence. Some samples displayed even fewer traces of potassium-40, leading to the conclusion that this isotope was scarcely present on proto Earth, gradually accumulating over billions of years.
The team conducted extensive simulations to demonstrate the increasing fraction of potassium-40 over time, reinforcing their hypothesis. “Scientists have been trying to understand Earth”s original chemical composition by combining the compositions of different groups of meteorites,” Nie noted. “But our study shows that the current meteorite inventory is not complete, and there is much more to learn about where our planet came from.”
This research not only sheds light on the early materials that contributed to the formation of Earth but also emphasizes the need for further exploration into the origins of our planet”s chemical makeup.
