Helium is the second most abundant element in the Universe, but it's relatively rare on Earth – so much so that some have called for a ban on party balloons to ward off a worldwide shortage. However, a team of scientists led by Diveena Danabalan of Durham University conducted a new study that indicates that there may be vast new sources of the gas in the western mountain regions of North America.
First detected in the spectrum of the Sun, in a century and a half helium has become a key resource in our high-tech world. The noble gas is used in cryogenics, MRI scanners, semiconductor manufacturing, welding, deep-sea diving, and blimps and balloons – though the latter makes up a surprisingly small fraction of the demand.
The problem is that even though helium makes up almost a quarter of all matter in the Universe, it's very rare on Earth with the main supply coming from natural gas wells in North America. This is because helium is a very light element that, once it escapes into the air, floats off into space. Hydrogen is lighter, but it's common on Earth because hydrogen is captured in molecules of water or organic compounds. Helium, on the other hand, forms no compounds even with itself except a few highly unstable ones under extraordinary laboratory conditions.
Recent studies have pointed to a drastic decline in known helium reserves and no large discoveries to replace them. This being the case, the fear is that we may run out of helium so soon that some scientists, such as Cambridge University chemist Peter Wothers, are calling for an end to its use in party balloons.
For the new study, a team of scientists from Durham and Oxford Universities looked at natural gas regions in North America, where they subjected gas samples from 22 wells in the United States and Canada to mass spectroscopy. By analyzing the isotopes of helium, neon, and argon, they were able to gain a better understanding of how helium is produced, transported, and trapped in the Earth.
Most helium on Earth is helium-4 (4He), which is produced by radioactive decay deep inside the planet. Over hundreds of millions of years, it migrates up to the crust, where it is released during periods of tectonic activity. By comparing the ratios of 4He with neon-20 (20Ne) in the helium-rich Hugoton-Panhandle gas field running through Texas, Oklahoma, and Kansas, the team found that released helium dissolves in groundwater, which transports it to natural gas deposits. According to Danabalan, This mechanism indicates that much more helium is waiting to be tapped than previously thought.
"We identified neon isotope tracers which show a strong association between helium and groundwater," says Danabalan. "This means that in certain geological regions, groundwater transports large volumes of helium into natural gas fields, where trapping potential is greatest. This suggests that we have probably underestimated the volumes of helium which are actually available to explore.
"On a continental scale, and we are talking about a line running right down the Rocky Mountains, we are seeing processes which are releasing the existing helium which has been built up deep underground over hundreds of millions of years," she continued. "In some places, like in Yellowstone Park in Wyoming, the deep helium is released directly into the atmosphere. In others, we are seeing that the deep helium which was released when the Rocky Mountains formed has percolated via the groundwater into the same underground reservoirs where we find natural gas. This means that there are almost certainly reservoirs of helium which we had not anticipated. More importantly, understanding how and why helium arrives in these reservoirs means that we now know where to look for new helium resources."
The team's findings were presented last week at the Goldschmidt geochemistry conference in Prague.
