Scientists Discover Unexplained Abundance of Rare Nuclear Fusion Fuel on Earth

An anonymous reader quotes a report from Motherboard: Scientists have discovered evidence that a key rare resource, called helium-3, is potentially ten times more common on Earth than previously known -- though the source of all this extra supply remains mysterious, reports a new study. The finding is important because helium-3 could serve as a foundation of limitless clean power for our civilization, but has been seen as inaccessible since it is largely found in outer space locations, especially the Moon. Helium-3 is an isotope of helium, which means it contains the same number of protons as this common element but a different number of neutrons. This isotope is considered a potentially powerful energy source for future fusion reactors, making it a star of science fiction as well as a sought-out resource in the real world. However, while small amounts of the substance are produced by geological processes and from the fallout of nuclear weapons testing, there is thought to be very little helium-3 available on Earth.

Now, scientists led by Benjamin Birner, a postdoctoral scholar in geosciences at the University of California San Diego, have captured evidence for a previously unknown abundance of helium-3 in the atmosphere, which 'presents a major puzzle in the helium-3 budget' and 'motivates a search for missing helium-3 sources on Earth, especially since helium-3 is considered an important, yet scarce, resource,' according to a study published on Monday in Nature Geoscience. Known sources of helium-3 on Earth only account for 10 percent of the surplus, the researchers said. Birner and his colleagues serendipitously uncovered this inferred surplus of helium-3 (3He) while tackling another challenging problem: measuring the overall rise in atmospheric helium as a result of human consumption of fossil fuels. The team pioneered a first-of-its-kind technique for estimating these anthropogenic helium emissions by examining another isotope, helium-4 (4He), which in turn led to the perplexing conclusion that there is some unknown source of helium-3 on our planet. 'We only measured the change in atmospheric 4He,' Birner said in an email. 'However, previous work by other researchers indicates that the helium isotopic ratio of the atmosphere (3He/4He) is roughly stable. Together these observations imply an increase in atmospheric 3He that matches the rise in 4He or we would see a change in the atmospheric isotope ratio.'

Helium-3 could be the ideal fuel for nuclear fusion, a potential energy source that mimics the same process that powers stars. Though nuclear fusion may not materialize as a practical power source for decades, assuming it is feasible at all, its potential to provide clean and limitless energy to the global human population makes it a tantalizing area of study. To that end, scientists across fields are likely to be interested in locating this unexplained surplus of helium-3 on Earth that has been implied by the new research. 'That increase of 3He is quite puzzling because we don't have a good explanation for the source of this 3He so far,' Birner noted. 'It's quite an important puzzle to solve also because 3He is an important and scarce resource for nuclear fusion reactors. Based on the reported uncertainties in previous studies of the atmospheric 3He/4He trend, the buildup of 3He looks significant, but our study clearly motivates a closer look at the atmospheric 3He/4He trend.'

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