At Lancaster University, one of the most valuable assets is stored in beer kegs – but not in a student bar. In a carefully locked laboratory, rows of metal kegs are arranged on shelves, linked by spindly copper pipework. They contain not prize beer but helium-3, one of the most expensive materials in the world, costing roughly $2,000 (£1,500) per litre.
"The lab has been going for 50 years or so. Back then, the helium was quite cheap," says Dima Zmeev, a senior lecturer at the university. "Our very wise predecessors stocked up." Today, however, helium-3 is in increasingly high demand, with applications in quantum computing and nuclear fusion. But the main source of the gas is tightly controlled: it comes from the decay of tritium, a form of hydrogen, inside nuclear weapons.
“Lancaster University stores valuable helium-3 in beer kegs, with demand soaring and plans to mine it from the moon.”
Around the world, tens of thousands of litres of helium-3 are likely produced this way every year, estimates David McCollum, distinguished scientist at Oak Ridge National Laboratory in Tennessee. But future demand could far exceed that supply, driving entrepreneurs and researchers to seek new sources. Though helium-3 exists on Earth, it is generally at very low concentrations.
Samples of moon dust, or regolith, from the Apollo missions suggest it may be present there at relatively high concentrations. As such, plans are now afoot to recover helium-3 from the moon.
Helium-3 is an isotope of helium, defined by the number of neutrons in the atom's nucleus. Helium-4, with one additional neutron, is the comparatively cheap version that fills children's party balloons. Zmeev uses helium-3 in physics experiments – for instance, filling tiny chambers with it to detect a type of mysterious dark matter particle. Should such a particle knock into one of the helium-3 atoms, it would make them jiggle, generating heat measurable as a slight temperature rise. The helium-3 can be reused again and again.
Scientists also mix helium-3 and helium-4 together at very low temperatures to create the lowest temperatures in the known universe, down to the millikelvin range (-273C). When helium-3 atoms gradually separate from the dilute mixture, they form a pure layer on top – a phase change that consumes energy, inducing a cooling effect like steam evaporating from hot water. This helium-3-based cooling, or dilution refrigeration, is crucial for quantum computers.
And helium-3 could also be used in some nuclear fusion reactors to one day create vast amounts of clean energy. As demand soars and terrestrial supplies remain limited, the race to tap the moon's resources is only beginning.