Helium shown to bond with iron

The discovery suggests there could be huge amounts of helium in the Earth’s core.

Researchers in Taiwan and Japan have used high-pressure from a laser-heated diamond anvil to bond helium with iron, suggesting implications for the make-up of the Earth's core.

As previous studies have only shown small traces of combined iron and helium, ~7ppm helium within iron, the researchers were surprised to find crushed iron compounds contained as much as 3.3% helium, about 5,000 times higher than previously seen.

The team believe the finding has implications for understanding Earth's origins, as helium in the core suggests a young Earth captured some gas from the solar nebula of hydrogen and helium that surrounded the early solar system. This means some of the Earth's water may have come from hydrogen in this ancient gas, offering a different perspective.

Iron and helium were crushed together under ~5-55GPa at 1,000K to ~3000K, by the team from the National Central University in Taiwan and the University of Tokyo, Institute of Science Tokyo and Hokkaido University, Japan.

Professor Kei Hirose from the University of Tokyo says those pressures correspond to roughly 50,000-550,000 times atmospheric pressure and the higher temperatures used could melt iridium, the material often used in car engine spark plugs due to its high thermal resistance.

'Helium tends to escape at ambient conditions very easily; everyone has seen an inflatable balloon wither and sink. So, we needed a way to avoid this when taking our measurements,'

Hirose says. 'Though we carried out the material syntheses under high temperatures, the chemical-sensing measurements were done at extremely cold, or cryogenic, temperatures. This way prevented helium from escaping and allowed us to detect helium in iron.'