Ancient Helium Leaking From Earth’s Core

Ancient Helium Leaking From Earth’s Core Offers Clues to Earth’s Formation

This image captured by the Hubble Telescope shows the center of the Lagoon Nebula. Nebulae are the main source of helium-3. The amount of He-3 leaking from Earth’s core suggests that the planet formed inside the solar nebula, according to new research. Photograph: NASA, ESA Photo….

According to a new study, helium-3, one of the rare isotopes of helium gas, is leaking from the Earth’s core. Since nearly all helium-3s came from the Big Bang, the gas leak suggests Earth may have formed inside a solar nebula. The hypothesis has been debated for a long time.

Helium-3 is detected in relatively small amounts on Earth’s surface. But until now, scientists didn’t know how much gas is leaking from the Earth’s core compared to the middle layers called the mantle.

In the new study, it was determined that an important source of helium-3 on Earth is the core. Helium-3 can also be formed in some natural processes, such as the radioactive decay of tritium. But helium-3 is mostly in the Sun nebula; formed in gigantic and swirling clouds of dust and gas. Our solar system is thought to have formed in such a nebula. Because helium is one of the oldest elements to form in the universe, most helium-3 can be traced back to the Big Bang.

As a planet grows, it accumulates substances around it. So the composition of the planets reflects the environment in which they were formed. To have a high density of helium-3 in its core, Earth must have formed inside a growing solar nebula; not on the nebula’s edges or in the shrinking phase.

Adding new clues to the mysteries of the formation of the Earth, the research also makes additional contributions to the theory that our planet formed inside the solar nebula.

The study was published earlier this week in the journal Geochemistry, Geophysics, Geosystems.

About 2,000 grams of helium-3 leaks from Earth each year, “big enough to inflate a table-size balloon,” says geophysicist Peter Olson of the University of New Mexico and lead author of the paper. “The fact that such large amounts of this isotope are still found in Earth’s interior is a miracle of nature and a beacon of Earth’s history.”

The researchers modeled helium at two important stages in Earth’s history: the early stage, when the planet was accumulating helium, and the second stage, where helium was lost following the formation of the Moon. The findings suggest that an object one-third the size of Earth slammed into the planet early about 4 billion years ago, which remelted Earth’s crust, causing most of the helium to fly away.

Using models for the behavior of the helium isotope as well as the leak rate of modern helium-3, the researchers estimate that there is between 10 teragrams (1013 grams) to one petagram (1015 grams) of helium-3 in the core. Olson says such a large amount indicates that Earth formed in the solar nebula. The high densities of the gas here must have allowed it to accumulate deep within the planet.

However, Olson says that future research will try to find other gases such as hydrogen formed in nebulae, and if these gases are determined to leak at similar speeds and locations to helium-3, this may indicate the core as the source. “There’s a lot more mystery than certainty,” he says.

Source: American Geophysical Union


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