Helium-3 could be bound-up with iron and oxygen deep within the Earth

The surprisingly high concentrations of helium-3 found at volcanic hotspots could be evidence for the existence of a rare helium-bearing chemical compound deep within the Earth. That is the conclusion of an international team of physicists who have calculated that crystalline FeO₂He could exist at temperatures and pressures found at the boundary between the Earth’s core and mantle. They have also shown that the material has acoustic properties associated with parts of this boundary.