|Ancient Helium Leaks From the Planet’s Core Provide New Clues to Earth’s Formation|
Ancient Helium Leaking From the Planet’s Core Provides New Evidence for Earth’s Formation
Image from the Hubble Telescope in the center of the Lake Nebula. According to a new study in the journal AGU Geochemistry, Geophysics, Earth Systems, the nebula is the primary source of helium-3, and the amount of He-3 leaking from the center of the Earth indicates the presence of planets within the solar nebula. Credit: NASA and the European Space Agency
Much helium remained at the core of the Big Bang, indicating that the Earth formed inside the solar nebula.
A new study points to a rare isotope of helium, helium-3, leaking from the Earth’s interior. Since nearly all helium-3 comes from the Big Bang, the gas leak adds evidence that Earth is forming inside the solar nebula, which has long been controversial.
Helium-3 has been measured in relatively small amounts at the Earth’s surface. But scientists don’t know how much is seeping out from the center of the Earth, from the middle layer, called the mantle.
A new study published today (March 26, 2022) in Geochemistry Geophysics Geosystems identifies the origin of Earth as a primary source of helium-3. Some natural processes can produce helium-3, such as the radioactive decay of tritium, but helium-3 is primarily produced in nebulae – huge clouds of gas and dust that are produced in our solar system. Since helium was one of the oldest elements in the universe, most of the element helium-3 dates back to the Big Bang.
As the planet grows, it accumulates elements around it, so its structure reflects the environment in which it forms. In order to have a high concentration of helium-3, the Earth must have formed in a rich solar nebula, not at its edges or in a weak phase.
The new study adds more clues to the mystery of Earth’s formation, providing more evidence for the theory that our planet formed inside a solar nebula.
The study was published in the journal AGU Geochemistry, Geophysics, Earth Systems, which publishes papers on geochemistry, physics, geology, biology and planetary processes.
About 2,000 grams of helium-3 leak from the Earth each year, said Peter Olsen, a geophysicist at the University of New Mexico, “enough to fill a balloon the size of your desk.” “It is a miracle of nature and a source in Earth’s history that there are still large numbers of these isotopes within the planet.”
The researchers modeled helium at two main stages in Earth’s history: initial formation, when planets accumulate helium and after the moon’s formation, helium is lost. Evidence suggests that an object about a third the size of Earth struck the Earth about 4 billion years ago, an effect that would remelt the crust and allow most of the helium to escape. Gas continues today.
Using recent models of helium-3’s leakage rate and the behavior of helium’s isotopes, the researchers estimated that the original portion contained 10 teragrams (1013 g) to 1 petagram (1015 g) of helium-3 — a significant amount, Olson said. During the formation of the Earth in the solar nebula, due to the high concentration of gas, it can accumulate in the depths of the Earth.
However, future work is looking for other nebula-producing gases, such as hydrogen, at the same rate as helium-3 and could be “strong evidence” of the origin as the source of the leak at the site, Olson said. “Mystery is more than certainty.”
Source: Peter L. Olson and Zachary D. Sharpe, American Geophysical Union, Direct News 99