helium-3

helium-3 (uncountable)

2. (physics) The rare isotope of helium, ³₂He, that has a single neutron.

   Hypernyms: helium < element < substance, material

   Coordinate term: helium-4 (the usual isotope on Earth)

   • 2017, BioWare, Mass Effect: Andromeda (science fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: H-047c Codex entry:

     With its magnetic field drastically weakened and much of its atmosphere lost, what remains intact of H-047c's surface is vulnerable to cosmic radiation. This has rendered the soil unable to support life, though it is a potential source of valuable helium-3.

   • 2025 September 2, Jeremy Bogaisky, “This Startup Is Racing To Be The First To Mine Helium On The Moon”, in Forbes‎^[1]:

     What Interlune is trying to do [the startup aims to develop robotic lunar mining camps] is far from child’s play. Helium-3, an industrially prized cousin of the isotope of the gas we use to fill party balloons, is rare on Earth. In 2024 it sold for $2,500 per liter, or roughly $19 million a kilogram, according to a report from Edelgas Group. […] The company faces daunting hurdles to get there. Though there is more helium-3 on the moon, it’s still far from abundant. Even if Interlune can find lunar regions with higher concentrations, collecting a commercially viable amount of helium-3 means developing and transporting to the moon machines that can chew through millions of tons of regolith, the loose debris that covers the lunar surface from billions of years of micrometeorite impacts. Autonomously. With no boots on the ground to repair them as they kick up dust more abrasive than anything on Earth. […] Interlune expects less than 1% of the gas they’ll get when they crush lunar regolith will be helium-3 – it’s estimated to exist only in the single- to double-digit parts per billion. To separate it from balloon helium and hydrogen, they’re cooling it all beyond negative 450 degrees Fahrenheit, at which point the other gases will liquefy and the helium-3 can be siphoned off.