In a groundbreaking study published in Nature Geosciences, researchers from MIT have reportedly found the first identifiable remnants of the materials that constituted the proto-Earth, the planet”s early form, which existed approximately four and a half billion years ago. This period was characterized by a tumultuous landscape filled with molten rock and lava.
The study reveals that the early Earth underwent drastic changes after a Mars-sized object collided with it when it was less than 100 million years old. This cataclysmic event not only obliterated a significant portion of the proto-Earth but also altered its chemical composition, leading scientists to believe that all evidence of this primordial planet had been lost.
However, the research team, led by co-author Nicole Nie, an assistant professor of earth and planetary sciences at MIT, asserts that they have made a significant discovery in meteorite samples collected globally. These meteorites act as time capsules, preserving chemical signatures from various epochs of the solar system”s 4.6 billion-year history.
The pivotal finding was an unusual potassium isotopic ratio identified in the meteorites, which differed from that of current Earth samples. On modern Earth, potassium-39 and potassium-41 are the most prevalent isotopes, while potassium-40 is present only in minor amounts. The meteorites, however, exhibited a distinct potassium isotopic anomaly, indicating a composition that predates the formation of Earth as we know it.
Nie explained, “In our analysis, we discovered that different meteorites possess varying potassium isotopic signatures. This suggests that potassium can serve as a valuable tracer for understanding the building blocks of Earth.” This led the team to investigate some of the oldest rock samples on Earth in search of a similar potassium signature.
Their findings pointed to an even lower presence of potassium-40 in these ancient rocks, suggesting that this isotope had a minimal presence in the proto-Earth, gradually increasing over billions of years. The researchers conducted extensive simulations that supported their hypothesis regarding the accumulation of potassium-40 over time.
Nie noted, “Previous efforts to ascertain Earth”s original chemical makeup relied on studying the compositions of various meteorite groups. Our work reveals that the current inventory of meteorites is incomplete, indicating that there is still much to learn about the origins of our planet.”
This research not only sheds light on the early conditions of Earth but also enhances our understanding of planetary formation in the solar system.
