A team of scientists at Harvard University believes they have found evidence that there is an ancient Earth within our planet. The team believes that a previously unexplained isotopic relationship from deep within the Earth could be a signal of the material before our world collided with another body the size of a planet, which led to the creation of the Moon. This could be an echo of an ancient Earth that existed 4,500 million years ago, before the proposed collision.
The current favored theory says that the Moon was formed 4.5 billion years ago when the Earth collided with a mass the size of Mars, nicknamed “Theia”. This theory states that the heat generated by the collision would have melted the entire planet before some of the debris splintered to create the Moon.
But now, the Harvard team, led by Associate Professor Sujoy Mukhopadhyay, believes they have found evidence that only part of the Earth melted and that an old part still exists within the mantle of the planet.
According to Professor Mukhopadhyay: “The energy released by the impact between Earth and Theia would have been enormous, certainly enough to melt the entire planet. But we believe that the impact energy was not distributed evenly throughout the ancient Earth. This means that a large part of the impacted hemisphere would probably have vaporized completely, but the opposite hemisphere would have been partially protected, and would not have completely melted. ”
The team analyzed the proportions of noble gas isotopes from deep within the Earth’s mantle and compared the results with the isotope ratios closest to the surface. They found that the ratio of 3He to 22Ne from the shallow mantle is significantly higher than the equivalent ratio within the mantle.
Professor Mukhopadhyay commented: “This implies that the last giant impact did not completely mix the mantle and there was not an entire ocean mantle of magma.”
More evidence comes from the analysis of the relationship of 129-Xenon to 120-Xenon. The material that reaches the surface from the deep mantle has a lower proportion than is normally found near the surface. Because 129-xenon is produced by the radioactive decay of 129-iodine, the isotopes locate the age of formation of the ancient mantle section within the first 100 million years of Earth’s history.
“The geochemistry indicates that there are differences between the isotope ratios of noble gases in different parts of the planet, and these must be explained. The idea that a very disruptive collision of the Earth with another body the size of a planet, the largest event in the geological history of our planet, was not completely fused and homogenized, challenges some of our notions about the formation of planets and the energy of giant impacts. “If the theory is correct, we may be seeing echoes of the ancient Earth, from a moment before the collision,” said Professor Mukhopadhyay.