Photo: NASA/ESA/Hubble / Courtesy
An extremely rare type of helium that was created shortly after the Big Bang is leaking from Earth’s core, according to a new study published in the journal AGU. Geochemistry, Geophysics, Geosystems.
Every year, according to scientists, about 2 kilograms of the rare isotope of helium gas, helium-3, escapes from the interior of the Earth. Helium-3 is believed to have been created just after the Big Bang about 13.8 billion years ago.
Since almost all of the helium-3 comes from the Big Bang, the gas leak adds evidence that the Earth formed inside a solar nebula – the molecular cloud that gave rise to the Sun – and not on its periphery or during its waning phase.
This is a detail about the birth of our planet that has long been unresolved and has been the focus of debate for a long time. The main thesis that supports this theory is based on the fact that as a planet grows, it accumulates material from its surroundings, so its composition reflects the environment in which it was formed.
Escape from the core of the Earth
Helium-3 has already been measured at the Earth’s surface in relatively small amounts. But scientists didn’t know how much seeped out of Earth’s core—particularly along the mid-ocean ridge system where tectonic plates meet—as opposed to its middle layers, called the mantle.
“Each year about 2,000 grams of helium-3 escape from Earth, enough to fill a globe the size of your desk. It is a wonder of nature, and a clue to Earth’s history, that there is still a significant amount of this isotope in the Earth’s interior,” lead study author Peter Olson, a geophysicist at the University of California, said in a statement. University of New Mexico.
Helium through Earth’s history
To estimate the abundance of primordial helium-3 in the core and track the exchange rate of helium-3 between the core and the mantle, the scientists modeled helium through Earth’s history. They mainly considered two key stages: early formation, when the planet accumulated helium, and after the formation of the Moon, after which helium was lost.
The model offers evidence that an object one-third the size of Earth collided with the planet early in its history, about 4 billion years ago. That impact would have remelted the Earth’s crust, allowing much of the helium to escape. The gas kept escaping.
The scientists also estimated “an enormous amount” between 10 teragrams and one petagram of helium-3 in the core.
“This large amount points to the formation of the Earth within the solar nebula, where high concentrations of gas would have allowed it to accumulate deep within the planet,” Olson said.
The researchers hope to find more clues to support their findings. For example, the finding of other gases created by the nebula, such as hydrogen, escaping from Earth from similar points and at a rate similar to that of helium-3, could be a “smoking gun” that would prove beyond doubt that the core is the source, Olson said. “There are many more mysteries than certainties.”
Edited by Felipe Espinosa Wang.