A team of Harvard scientists may have found an indication that a portion of an ancient Earth exists inside our planetâ€™s mantle.
A study presented at the Goldschmidt conference in Sacramento, California, claims that the previously inexplicable isotope ratio from the depths of the Earth may be an â€śechoâ€ť of the ancient Earth that existed before the collision with another celestial body, which is estimated to have led to the formation of the Moon 4.5 billion years ago.
According to the authors of the study, the ratio may represent a signal from a material that existed prior to the moment of the collision.
Scientists of the Harvard University led by Associate Professor Sujoy Mukhopadhyay believe that only a portion of the Earth melted as a result of the collision, and that in the depths of our planetâ€™s mantle there still exists a part of the ancient Earth.
Scientists have studied the isotope ratio of noble gases from the depths of the Earthâ€™s mantle and compared it to the isotope ratio of the gases found closer to the surface. They found that the ratio of 3He to 22Ne from the surface layers of the mantle is much higher than the one of its deeper layers.
The analysis of the 129-Xenon and 130-Xenon ratio also confirms the hypothesis suggested by the researchers. Material which has been rendered to the surface from the deep mantle has a lower ratio than the one which is typically located near the surface.
Since the 129-Xenon is produced by the radioactive decay of 129-Iodine, these isotopes indicate that the ancient part of mantle was formed during the first 100 million years of the Earthâ€™s evolution.
Scientists believe that this theory explains the differences between the isotope ratios of noble gases in different parts of the Earth.
As Professor Mukhopadhyay said: â€śThe geochemistry indicates that there are differences between the noble gas isotope ratios in different parts of the Earth, and these need to be explained. The idea that a very disruptive collision of the Earth with another planet-sized body, the biggest event in Earthâ€™s geological history, did not completely melt and homogenize the Earth challenges some of our notions on planet formation and the energetics of giant impacts. If the theory is proven correct, then we may be seeing echoes of the ancient Earth, from a time before the collisionâ€ś.
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