Helium is the second most abundant element in the universe, making up about 25 percent of all mass, but it's relatively rare on Earth. And while it's technically renewable, emitted slowly as uranium decays, it's also one of the few elements light enough to literally leak off the planet. Our air tends to hold 5.2 parts per million.

Having so little helium might not matter if we only used it to float balloons and distort voices. Those are two of its most well-known applications, but it also performs many other, more practical duties for humanity. And given the high demand for helium in recent years, some experts have begun worrying about shortages.

Hopes are rising, however, thanks to a discovery last year of a huge helium reserve in Tanzania. A new 2017 analysis shows the field may hold even more helium than originally believed. Initially, experts estimated the size of the reserve to be about 54 billion cubic feet, or about one-third of the world's known reserves. But Thomas Abraham-James, a geologist and CEO of Helium One, tells Live Science that new measurements indicate it's more like 98 billion cubic feet — nearly double the size.

"This is a game changer for the future security of society's helium needs," says one of the discoverers, University of Oxford geochemist Chris Ballentine, in a statement. And on top of the stash, he adds, "similar finds in the future may not be far away."

Why is helium so important?

Aside from being nontoxic and chemically inert, helium has a unique combination of traits — like low density, low boiling point and high thermal conductivity — that make it useful for a variety of niche applications. They may not be as visible as floating balloons, but several are more important to modern life, such as:

Magnetic resonance imaging (MRI): About 20 percent of all the helium used by humans goes to MRI, a valuable imaging technique used in medical diagnosis, analysis and research. MRI scanners feature superconducting magnets, which generate lots of heat, and they widely rely on liquid helium for cooling. Due to its low specific heat, low boiling point and low melting point, "there is no foreseen substitute for helium in this very important use," according to Geology.com.

MRI scan A patient undergoes an MRI scan at Argenteuil hospital in a suburb of Paris. (Photo: Fred Dufour/AFP/Getty Images)

Keeping science cool: Liquid helium serves as a coolant in many other capacities, too, including satellites, telescopes, space probes and particle colliders like the Large Hadron Collider. Helium gas is also used in some pressure-fed rocket engines, and as a purging gas that can safely displace extremely cold liquids from fuel tanks or fuel-delivery systems without freezing.

liquid helium A tank of liquid helium, which is used as a coolant in many scientific instruments. (Photo: Shutterstock)

Industrial leak detection: Because of the way helium rushes toward a leak, it's often used as a "tracer gas" in industrial high-vacuum or high-pressure systems, helping operators detect breaches quickly after they occur.

leak detection machine A leak-detection machine produced by the Swedish company Kontikab. (Photo: Baravara/Wikimedia Commons)

Weather balloons and blimps: Beyond party favors and parade floats, helium keeps lots of different things afloat, and without the infamous flammability of hydrogen. Helium gas is still carrying around weather balloons, for example, and it still lifts blimps used for aerial views, advertising and science.

high-altitude science balloon This balloon carried NASA climate-science instruments into the upper atmosphere in 2013. (Photo: NASA)

Breathing gas: Helium can be blended with oxygen to create breathing gases like heliox, which is commonly used in health care as well as scuba diving. The element is well-suited for this role since it's chemically inert, has low viscosity and is easier to breathe under pressure than other gases.

heliox Scuba divers' air tanks often include some helium gas as well as oxygen. (Photo: Shutterstock)

Welding: In arc welding, a process that welds materials using an electric arc, helium often serves as a shielding gas to protect materials from contamination or damage.

arc welding Certain types of arc welding rely on helium as an inert shielding gas. (Photo: Photo Dudes/Flickr)

Manufacturing: Thanks to its low reactivity, low density and high thermal conductivity, helium gas is also a popular protective gas in other fields, from growing silicon crystals for semiconductors to manufacturing optical fibers.

electronic circuit Helium can help with the production of materials for semiconductors used in electronic circuits. (Photo: Shutterstock)

How do we get helium?

As radioactive decay releases helium in the Earth's crust, some of the gas drifts into the atmosphere, where it can float upward and even leak into space. Some also gets trapped in the crust, forming underground deposits similar to other gases like methane. That's where all the helium we use comes from.

Until now, helium reserves had never been found on purpose — just as a bonus during oil and natural gas drilling, and even then only in small amounts. But researchers from Oxford and Durham universities, along with a Norwegian company called Helium One, have developed a new way to search for hidden helium. And according to their report, the first use of this method has led to a "world-class" and "life-saving" discovery in the Tanzanian East African Rift Valley.

Batur volcano, Indonesia The discovery in Tanzania suggests helium may lurk in other volcanic regions, too. (Photo: Shutterstock)

Why is this discovery such a big deal?

The researchers estimate they found about 54 billion cubic feet (BCf) of helium in just one part of the valley, which is enough to fill 1.2 million MRI scanners. And given all the things MRI can do — like letting doctors non-invasively examine a patient's internal organs, monitor tumor growth, study inflammation or check on a developing fetus — the relevance for health care alone seems pretty significant.

"To put this discovery into perspective," Ballentine writes, "global consumption of helium is about 8 BCf per year and the United States Federal Helium Reserve, which is the world's largest supplier, has a current reserve of just 24.2 BCf. Total known reserves in the USA are around 153 BCf."

On top of the helium itself, this may set the stage for more discoveries in other volcanic regions. The researchers found that volcanoes can provide the intense heat needed to release helium from ancient rocks, and linked that process to rock formations that trap the gas underground. In this part of Tanzania, volcanoes scorched helium out of deep rocks and trapped it in gas fields closer to the surface.

There is a catch, though: If these "gas traps" are too close to a volcano, the helium could be diluted by volcanic gases. "We are now working to identify the 'goldilocks zone' between the ancient crust and the modern volcanoes where the balance between helium release and volcanic dilution is 'just right,'" says Diveena Danabalan, a Ph.D. student at Durham University's Department of Earth Sciences.

Once that balance becomes clearer, helium could become easier to find.

"We can apply this same strategy to other parts of the world with a similar geological history to find new helium resources," explains Oxford University geochemist Pete Barry, who sampled gases in the study. "Excitingly, we have linked the importance of volcanic activity for helium release with the presence of potential trapping structures, and this study represents another step toward creating a viable model for helium exploration. This is badly needed given the current demand for helium."

Having more helium would be cause for celebration, but first, it's worth noting that whatever they contain, disposable party balloons aren't as benevolent as they seem. So, even if it turns out we can spare some extra helium, let's not get carried away.

Editor's note: This story was updated since it was originally published in June 2016.