Helium Found in Earth's Core Suggests New Insights into Planetary Formation

Tokyo, Japan (SPX) Mar 01, 2025
A groundbreaking study from researchers in Japan and Taiwan has revealed that helium, an element typically considered chemically inert, can bond with iron under extreme pressures. Using a laser-heated diamond anvil cell, scientists observed this phenomenon, suggesting that substantial amounts of helium may exist in Earth's core. This discovery could challenge long-standing theories about the planet's internal composition and formation history while shedding light on the primordial nebula from which the solar system emerged.

Volcanic eruptions often release a variety of materials, including traces of what is known as primordial helium. This differs from the common helium isotope, 4He, which consists of two protons and two neutrons and is generated by radioactive decay. Primordial helium, or 3He, on the other hand, contains only one neutron and is not naturally formed on Earth. The presence of high 3He/4He ratios in volcanic rocks, particularly in Hawaii, has led scientists to believe that reservoirs of primordial helium-containing material exist deep within the mantle.

However, graduate student Haruki Takezawa and a research team led by Professor Kei Hirose from the University of Tokyo's Department of Earth and Planetary Science have now challenged this assumption through an innovative high-pressure experiment.

"I have spent many years studying the geological and chemical processes occurring deep within the Earth. Given the extreme temperatures and pressures involved, our experiments must replicate these conditions. To do so, we frequently employ a laser-heated diamond anvil cell, which can subject materials to extreme pressures," explained Hirose. "In this experiment, we compressed iron and helium together at pressures ranging from 5 to 55 gigapascals-equivalent to 50,000 to 550,000 times atmospheric pressure-and temperatures between 1,000 and nearly 3,000 kelvins. These higher temperatures can even melt iridium, a material known for its high thermal resistance and common use in spark plugs."

Earlier studies had only detected trace amounts of helium in iron, with concentrations reaching approximately seven parts per million. However, in their latest experiments, Hirose's team discovered iron compounds containing up to 3.3% helium-a concentration about 5,000 times higher than previously recorded. The researchers attribute this unexpected finding to a key methodological innovation in their experiment.

"Helium tends to escape easily under normal conditions-everyone has seen a balloon deflate over time. To prevent helium loss while taking our measurements, we synthesized the material at high temperatures but conducted chemical analysis at cryogenic temperatures. This approach allowed us to detect and quantify helium within iron more effectively," said Hirose.

The presence of helium in Earth's core carries significant implications for our understanding of planetary formation. If helium was incorporated into the core, this suggests that the young Earth retained some of the gases from the primordial solar nebula, which consisted mainly of hydrogen and helium. This raises the possibility that Earth's early water supply may have originated from hydrogen in that ancient gas, offering fresh insights into the planet's developmental history.

Research Report:Formation of Iron-Helium Compounds under High Pressure