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Japanese and Taiwanese researchers have concluded that in the earth’s core may contain large amounts of primary helium.
For a long time, helium was believed to be an inert gas, but scientists argue that in the Earth’s core it can bind to iron under extremely high pressure. The researchers used a diamond anvil cell that was heated with a laser and observed the interaction of helium with iron.
This discovery challenges conventional theories about the internal structure of the planet and its formation history, and may provide insight into how the nebula of the early solar system was formed from hydrogen and helium.
Volcanic eruptions primarily bring minerals and rocks to the surface, but also emit traces of an inert gas known as primary helium. Unlike the common isotope of helium-4 (⁴He), which consists of two protons and two neutrons and is continuously produced by radioactive decay, primary helium-3 (³He) has only one neutron and is not produced on Earth.
Given the high ratio of 3He/4 He, which was found in volcanic rocks, has long been believed by researchers to be deep in the Earth’s mantle are primary materials containing helium-3 However, graduate student Haruki Takezawa and members of Professor Kei Hirose’s group at the Department of Earth and Planetary Sciences at the University of Tokyo are now challenging this view by offering a new perspective on the familiar experiment of crushing things.
«I have spent many years studying the geological and chemical processes that occur deep in the Earth’s interior. Given the high temperatures and pressures involved, experiments to investigate some aspect of this environment must reproduce these extreme conditions. Therefore, we often turn to a laser-heated diamond anvil cell to apply such pressures to samples and see the results In this case, we pulverized iron and helium together under pressures of about 5-55 gigapascals and at temperatures ranging from 1000 to nearly 3000 kelvin. These pressures correspond to pressures about 50,000 to 550,000 times higher than atmospheric pressure, and higher temperatures could melt iridium — a material often used in automotive spark plugs because of its high thermal stability», — explains Professor Kei Hirose.
Previous studies had found only trace amounts of iron-helium combinations of 7 iron particles per million helium particles. However, the researchers found that the crushed iron compounds contained up to 3.3% helium, which is about 5 thousand times more than previously found.
«Helium tends to evaporate very easily under ambient conditions; everyone has seen a balloon wilt and shrink. We therefore needed a way to avoid this during our measurements. Although we synthesized the materials at high temperatures, the chemical measurements were performed at extremely low, or cryogenic, temperatures. This prevented the helium from evaporating and allowed us to detect helium in the iron», — said Kei Hirose.
This discovery could be important for understanding how our planet formed. The presence of primary helium in the Earth’s core indicates that the young planet probably captured some of the gas from a solar nebula of hydrogen and helium that surrounded the solar system in the early stages of formation This could also mean that some of the water on Earth could have been formed from hydrogen.
The study was published in the journal Physical Review Letters
Source: SciTech Daily