Primordial helium, formed billions of years ago, seems to be leaking out of the Earth’s core

(ORDO NEWS) — Ancient, primordial helium from the Big Bang is leaking out of the Earth‘s core, scientists say in a new study.

There is no reason to be alarmed. The earth does not deflate like a sad balloon. But this means that the Earth formed inside the solar nebula – the molecular cloud from which the Sun was born, and this detail of the birth of our planet remained unresolved for a long time.

It also suggests that other primordial gases may leak from the Earth’s core into the mantle, which in turn could provide information about the composition of the solar nebula.

Helium on Earth is represented by two stable isotopes. The most common is helium-4, the nucleus of which contains two protons and two neutrons. Helium-4 accounts for about 99.99986 percent of all helium on our planet.

Another stable isotope, only about 0.000137 percent of Earth’s helium, is helium-3, with two protons and one neutron.

Helium-4 is basically a product of the radioactive decay of uranium and thorium produced right here on Earth. Helium-3, by contrast, is mostly primordial, formed in the moments after the Big Bang, but it can also be produced from the radioactive decay of tritium.

It is the helium-3 isotope that has been found leaking from the Earth’s interior, mainly along the system of mid-ocean volcanic ridges, which gives us a fairly accurate idea of ​​the rate of its release from the crust.

That rate is about 2,000 grams (4.4 pounds) per year, “about enough to fill a balloon the size of your desk,” explains geophysicist Peter Olson of the University of New Mexico.

“It’s a miracle of nature and a clue to Earth’s history that significant amounts of this isotope still exist in the Earth’s interior.”

What is less clear is the origin: how much helium-3 can escape from the core, and how much is in the mantle.

This would make it possible to determine the source of the isotope. When the Earth formed, it accumulated material from the dust and gas floating around the newborn Sun.

A significant amount of helium-3 could only be inside the planetary core if it was formed in a flourishing nebula. That is, not on its outskirts and not in the process of dispersion and expansion.

Olson and his colleague, geochemist Zachary Sharp of the University of New Mexico, conducted a study by simulating the Earth’s supply of helium as it evolved. First, during its formation, when the protoplanet accumulated and included helium, and then after the Great Collision.

Astronomers believe that during this impact, a Mars-sized object crashed into a very young Earth, sending debris into Earth’s orbit that eventually recombined to form the Moon.

During this event, which would have resulted in the remelting of the mantle, much of the helium trapped in the mantle would have been lost. The core, however, is more impact resistant, suggesting that it could be a fairly efficient reservoir for storing helium-3.

In fact, this is exactly what the researchers found. Using the current rate of helium-3 leakage from the interior, as well as models of the behavior of helium isotopes, Olson and Sharp found that in the core of our planet there is probably from 10 teragrams (1013 grams) to a petagram (1015 grams) of helium-3.

This suggests that the planet must have formed inside a thriving solar nebula. However, several uncertainties remain. The likelihood that all conditions have been met to keep helium-3 in the Earth’s core is moderately low – meaning there may be less isotope than the team’s work suggests.

However, it is possible that there is also a large amount of primordial hydrogen in the core of our planet, which fell into the same process that could lead to the accumulation of helium-3. Finding evidence of a hydrogen leak could help confirm the findings, the researchers say.


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