What is Helium-3 and could we get it from the moon?

One of the most valuable assets owned by Lancaster University is stored in beer kegs. But it’s not in one of the student bars. In a carefully locked laboratory, rows of metal kegs are arranged on shelves and linked together with spindly copper pipework. The containers aren’t loaded with prize beer but rather a gas called helium-3, one of the most expensive materials in the world. A single litre costs roughly $2,000 (£1,500), though the price can fluctuate significantly based on supply and demand. "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."

In the near future, more people could be looking to build up such a stockpile. Helium-3 has critical applications spanning quantum computing, advanced physics research, and holds immense, albeit distant, promise for clean nuclear fusion energy. However, the main source of it today is tightly controlled – it comes from nuclear weapons. Specifically, it is a byproduct of the radioactive decay of tritium, a heavy isotope of hydrogen, used in the boost stage of thermonuclear weapons. Around the world, tens of thousands of litres of helium-3 are likely to be produced this way every year, estimates David McCollum, a distinguished scientist at Oak Ridge National Laboratory in Tennessee. But future demand, especially from nascent quantum technologies and aspirational fusion projects, could far exceed that finite and strategically sensitive supply.

Some entrepreneurs and researchers contend that humanity urgently needs new sources of helium-3. While it exists in the Earth’s ground, it is generally at very low concentrations, trapped in the crust from primordial origins or rare geological processes. Our planet’s strong magnetic field largely shields us from the solar wind, the primary source of helium-3 in the solar system. However, samples of moon dust, or regolith, brought back by the Apollo missions, suggest it may be present there at relatively high concentrations, unimpeded by an atmosphere or magnetic field. As such, ambitious plans are now afoot to recover helium-3 from the moon, transforming science fiction into a potential economic reality.

Helium-3 is a rare, stable isotope of helium, defined by the number of neutrons in the atom’s nucleus. Unlike the common helium-4, which has two protons and two neutrons, helium-3 possesses two protons and only one neutron. This slight difference in atomic structure gives it unique quantum properties and makes it invaluable for certain scientific and technological applications. Helium-4, with one additional neutron, is the comparatively cheap version – a gas that fills children’s party balloons and is abundant on Earth, primarily extracted from natural gas deposits.

Zmeev uses helium-3 in highly sensitive physics experiments. For example, he fills tiny chambers with the stuff in a project 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 all jiggle, generating heat. This slight, measurable temperature rise could be the signature scientists are looking for. The beauty of this application is that the helium-3 can be re-used again and again, making the initial investment more palatable.

Beyond dark matter, scientists 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). This phenomenon, known as dilution refrigeration, occurs because when helium-3 atoms gradually separate from a dilute mixture containing the two isotopes, they form a pure helium-3 layer on top. This separation is a phase change that consumes energy, inducing a cooling effect, much like when steam evaporates off a cup of hot water. Helium-3-based cooling, or dilution refrigeration, is crucial for maintaining the delicate quantum states of qubits, the fundamental building blocks of quantum computers, which must operate at near absolute zero temperatures to function coherently.

One company planning to extract helium-3 from the moon is Interlune, based in Seattle. "We’ve spent the last four years developing, prototyping and testing technologies… We have a team of 30 people, and growing," says Rob Meyerson, co-founder and chief executive. Meyerson was president of Blue Origin, Jeff Bezos’ rocket company, between 2003 and 2018, bringing significant aerospace experience to the venture. One of Interlune’s other co-founders is Harrison "Jack" Schmitt, now in his 90s, who walked on the moon during the Apollo 17 mission. Schmitt, a geologist by training, has long advocated recovering helium-3 from lunar regolith, envisioning it as a future fuel source for clean energy.

Interlune has tested some of its equipment during parabolic flights, in which a plane flies in a big arc to simulate zero gravity, allowing for testing in microgravity conditions. The firm’s kit could be integrated into a lunar lander as early as autumn 2027, says Meyerson, aiming for initial reconnaissance and validation of extraction techniques. Eventually, Interlune aims to place autonomous, regolith-shovelling excavators on the moon to scoop up the powdery material and process it. The idea is to crush and churn the regolith, heating it to release not just helium-3, but also other valuable volatiles like hydrogen and water, which are contained within it from billions of years of solar wind bombardment.

The prospect of lunar helium-3 also ties into the long-term dream of nuclear fusion. While current fusion research primarily focuses on deuterium-tritium reactions, which produce energetic neutrons that cause material damage and radioactivity, a deuterium-helium-3 fusion reaction is often described as "aneutronic." It produces charged particles (protons) that can be directly converted into electricity, offering a potentially cleaner and more efficient energy source. The challenge is that D-He3 fusion requires significantly higher temperatures and more effective magnetic confinement than D-T fusion, pushing it further into the future. However, if these engineering hurdles can be overcome, the moon’s abundant helium-3 could be the key to limitless, clean energy on Earth.

However, significant uncertainties cloud the lunar helium-3 venture. No-one knows with certainty what kind of helium-3 concentrations are uniformly present on the moon. Paul Burke, at Johns Hopkins Applied Physics Laboratory, cautions that Apollo regolith samples might have lost some of their helium-3 during their long journey back to Earth and subsequent storage, potentially skewing our understanding of how much is truly there. Plus, there might not be as many helium-3 hotspots as hoped, or they could be at depths that are difficult to access with current or near-future technology. "It’s important that we understand where the helium-3 is," says Burke.

As Space News reported last year, lunar concentrations – perhaps between a few parts per billion (ppb) and 20-something ppb – could require excavating and processing hundreds of thousands of tonnes of the regolith just to obtain one kilogram of Helium-3. A "mountain-moving" prospect, says Burke, highlighting the sheer scale of the operation required. "We’re not ignoring the fact that we’ve got to process large amounts of regolith," says Meyerson. Is the plan economically sensible given the vast logistical and energy costs? "We have run the numbers… for everything we need to get to the moon, extract the [Helium-3] and bring it back to Earth," he asserts. However, Interlune declined to share those numbers with the BBC, or estimates for the total cost of developing its technology and establishing a lunar mining operation, leaving much to speculation.

Another US company, Astrotech Corporation, has also announced its intention to go to the moon. In its case, via a SpaceX Starship rocket, leveraging the next generation of heavy-lift launch vehicles. Astrotech would extract helium-3 from regolith by heating it up, a method that requires substantial power but could be efficient for gas extraction. Tom Pickens, chief executive and chief technology officer, acknowledges the immense difficulty: "All of it is challenging." In previous space-based applications, his company made mass spectrometers, sophisticated instruments that identify materials such as chemical elements and measure their concentrations, providing a basis for their expertise in lunar resource analysis. Work continues on a prototype for lunar helium-3 extraction, and Pickens is bullish: "You’ll see it." The company has "seven or eight" people working on the project, he adds, indicating a smaller, more focused team.

Quantum computers could eventually require thousands of litres of helium-3, depending on their design and the expansion of the quantum industry, suggests McCollum. He and colleagues recently published a paper scrutinising the energy and resource requirements of these cutting-edge devices, underscoring the potential demand surge. This means that the lunar helium-3 projects are already attracting significant interest and investment. Helsinki-based quantum computing company Bluefors, a leading provider of ultra-low temperature dilution refrigerators, has signed a $300m (£223m) deal with Interlune, for 10,000 litres of helium-3 annually from 2028-37. This substantial pre-order demonstrates a clear market signal and confidence in Interlune’s ability to deliver, despite the inherent risks.

But there are alternatives, and not everyone is convinced that lunar mining is the only path forward. Some scientists are working on methods of cooling quantum computers that don’t rely so heavily on helium-3, for example, points out Richard Easther at the University of Auckland. Innovations in cryogenics could reduce dependency or even find substitutes. And helium-3 hunters might be able to recover useful volumes from the Earth’s crust after all. Pulsar Helium, headquartered in Portugal, is actively investigating the presence of helium-3 at a site in Minnesota. Concentrations there are around 12ppb, says Peter Barry, a geochemist at Woods Hole Oceanographic Institution and a scientific advisor to the company. While still low, conventional drilling could potentially yield economically viable quantities of helium-3 from the ground there, especially if trapped in unique geological formations. Barry optimistically adds, "Minnesota is a lot easier to get to than the moon," a sentiment that encapsulates the immense challenges and costs associated with off-world resource extraction. The quest for helium-3 highlights humanity’s insatiable demand for rare resources and the incredible lengths we are willing to go to secure them, whether digging deep into our own planet or reaching for the stars.