NewsChemistryA new iron compound hints primordial helium hides in Earths coreHelium atoms filled gaps in iron crystals under high pressure and temperature Under high temperature and pressure, helium atoms (red circles) move into the spaces between iron atoms (red circles with black centers) in a piece of iron metal, as show in this map called an electron localization function.Han Hsu/ National Central UniversityBy Skyler Ware45 seconds agoScientists have coaxed one of the universes most stubborn elements into a new compound.Formed under intense pressures, the newly discovered compound packs helium atoms into crystalline iron, researchers report February 25 in Physical Review Letters. The compound joins a short list of materials that incorporate the normally unreactive element and suggests that helium from the early solar system could be stored in the iron that makes up Earths core.Helium is one of the least reactive elements on the periodic table. Like the other noble gases, helium doesnt gain or lose electrons easily and so does not normally form chemical compounds. But under extremely high pressures, helium can interact with a few other elements, including nitrogen and sodium and now iron, research shows.An iron-helium compound, shown here in artificial color using a technique called secondary ion mass spectrometry, forms under high temperature and pressure. Blue and black areas mark the background, while the orange and red area represents the sample. 2025 Hirose et al. CC-BY-NDTo make the new iron compound, physicist Kei Hirose of the University of Tokyo and his colleagues squeezed iron and helium together in a diamond anvil cell, a high-pressure device that subjected the elements to pressures greater than 50,000 Earth atmospheres and temperatures above 1,000 degrees Celsius. This compression formed crystals containing both iron and helium.The volume of the crystal formed was larger than that of a crystal of pure iron at the same pressure, the team found. The researchers attributed this increase to helium ions packing into interstitial sites, the tiny spaces between iron atoms in the crystal. But the helium atoms dont bond directly to iron theyre too unreactive, even at extreme conditions.