The remains of an old Earth, going back to the period when another planet collided with ours to create the moon, may yet be trapped deep below the Earth’s mantle, according to a team of Harvard scientists.
If you thought seeing the Earth from orbit was exciting, just wait till you see this: Harvard University scientists think they have discovered evidence that an ancient Earth exists within the Earth.
The researchers believe that a hitherto unexplained isotope ratio found deep within the Earth might represent a signal from material that existed before the Earth collided with another planet-sized entity, resulting in the formation of the Moon. This might be a remnant of a 4.5 billion-year-old Earth that existed before the alleged collision.
According to popular belief, the Moon was formed 4.5 billion years ago when the Earth collided with “Theia,” a mass the size of Mars.
According to this idea, the heat from the impact melted the whole planet before part of the debris spun out to form the Moon.
However, a Harvard team led by Associate Professor Sujoy Mukhopadhyay believes they’ve discovered evidence that only a portion of the Earth melted, and that an older portion of the Earth still persists within the Earth’s mantle.
Professor Mukhopadhyay claims that:
“The energy generated by the Earth-Theia collision would have been enormous, easily enough to destroy the whole planet.” However, we believe the impact energy was not dispersed uniformly throughout the ancient Earth.
“This means that while a large portion of the hit hemisphere would have been fully vaporized, the opposing hemisphere would have been partially protected and not completely melted.”
The researchers examined the ratios of noble gas isotopes from deep below the Earth’s mantle to those from closer to the surface. They discovered that the shallow mantle’s 3He to 22Ne ratio is much larger than the comparable ratio deep within the mantle.
Professor Mukhopadhyay made the following observation:
“This suggests that the previous large impact did not thoroughly mix the mantle and that an entire mantle magma ocean did not exist.”
Analysis of the 129-Xenon to 120-Xenon ratio adds to the evidence. The percentage of material delivered to the surface from the deep mantle is smaller than that found near the surface.
The isotopes place the creation age of the ancient piece of mantle to within the first 100 million years of Earth’s existence since 129-Xenon is created by the radioactive decay of 129-Iodine.
“Geochemistry suggests that the noble gas isotope ratios in different portions of the Earth varies, and these variances must be explained.”
“The thought that the Earth did not totally melt and homogenize after colliding with another planet-sized body, the most disruptive event in Earth’s geological history, calls into question several of our assumptions about planet formation and the energetics of huge impacts.”
“If the idea is accurate, we may be experiencing echoes of the early Earth from before the impact,” Professor Mukhopadhyay speculated.
According to Carnegie Institution Department of Terrestrial Magnetism Professor Richard Carlson:
“This intriguing discovery adds to the observable evidence that critical features of Earth’s composition were formed during the planet’s catastrophic birth and provides a novel look at the physical processes by which this may occur,” says the researcher.
The Harvard team’s findings are consistent with those of a German study, which support the notion that the Moon was created 4.5 billion years ago following a cataclysmic collision with a planet-sized mass.
At the Goldschmidt Geochemistry Conference in California, both the Harvard and German teams reported their findings.