Helium could become the clean energy source of the 21st century. Colossal reserves of the gas are waiting to be mined from the moon's surface, and returned to Earth as a fuel for 100% green, radioactive-free nuclear power. So what are the hurdles to this endeavour?
Helium has a fascinating back story.
Here on Earth, helium is a rare resource derived from limited reserves of natural gas trapped in the Earth's crust. It has a handful of advanced medical and industrial applications, not to mention party balloons.
However, the Earth-shattering potential for helium lies in nuclear fusion: a technology not yet fully developed but promises abundant clean energy for centuries to come.
Scientists have long known that, despite its rarity on Earth, helium exists in abundance in space. There are thought to be vast reserves of the isotope helium-3 trapped just under the surface of the moon with a realistic potential for mining.
Its value as a nuclear power source pitches it at $3 billion per tonne, and even relatively small amounts shipped back to Earth could power entire countries year-round.
Combine the potential of lunar mining and nuclear fusion reactors and what have you got? An end to humanity's reliance on non-renewable fossil fuels and protection for life on Earth from continued shifts in the global climate.
Such a transition is not only worth trillions in economic terms, but will pave the way for the next industrial and political superpower.
The helium rush is on.
How Helium is Created
The universe is predominantly made up of hydrogen and helium as a result of the nuclear fusion that takes place inside stars.
As the two lightest elements, they are the building blocks of all heavier elements, which are simply an accumulation of more and more protons, neutrons and electrons.
Hydrogen, the most common element in the universe, makes up most of the stars in the night sky and of course our very own sun. It's usually composed of one proton and one electron (and zero neutrons; see my article Atoms 101 if you have no idea what I'm talking about).
Stars are hot. Really hot. And this energy has all the hydrogen atoms shooting around - with the eventual outcome of colliding into one another. Usually when this happens, they break apart.
However, sometimes the collision simply causes one proton to lose its positive charge and convert to a neutron, thanks to the weak nuclear force.
The result is an atom of deuterium: a stable isotope of hydrogen with one proton, one neutron and one electron. The collision also releases energy, ensuring stars stay hot, just as we puny humans like it.
But we still don't have helium yet, so how is helium created? Picture the hydrogen atoms and deuterium isotopes whizzing around inside the star (see below).
Eventually these collide too, giving us an isotope of helium-3 (by adding another proton to deuterium).
Finally, when two atoms of helium-3 smack together, we get an atom of helium-4, plus a couple of hydrogen atoms as a nice bonus.
Hundreds of billions of stars are doing this in every galaxy, which is why there is simply a lot of helium hanging around in the cosmos. Not only is it rife inside stars, but it's also ejected on a massive scale and dispersed by solar winds, which is how it ends up in excess on the moon. A lot more about this later.
Earth's magnetosphere protects us from solar winds and the accompanying helium bombardment. However, the gas is created in small quantities on Earth through a separate process in rock.
Helium is emitted as alpha particles (which Ernest Rutherford established are essentially helium nuclei - just add electrons) from the radioactive decay of heavy elements such as uranium, thorium and radium.
This process of decay, however, takes billions of years which is what makes helium such a finite resource on our planet.
The resulting helium pockets in the Earth's crust can be mined by humans, or when formed in the upper mantle, can be released by volcanic activity and lost into the atmosphere.
The helium in our atmosphere amounts to five-millionths or 0.000005% of it, to be precise. However its lightness means it escapes from our gravity with ease, so each time we deploy the stuff in party balloons or industrial applications, a little more is permanently lost to space.
You can't normally see, smell or taste helium, but it does glow in an electric field.
The Discovery of Helium
Helium was discovered in stars back in the 1800s with the use of a spectrometer. This is a tool which diffracts light, enabling the observer to measure the optical properties of any substance, near or distant.
A spectrometer exploits the fact that electrons have specific energies which differ according to their orbital. When an electron relaxes to a lower orbital it emits light which shows up as an emission spectrum.
Conversely, when an electron is excited to a higher orbital it absorbs light which shows up on the absorption spectrum.
As you can see below, different elements have different optical fingerprints, allowing us to identify them even from vast distances across space.
Prior to 1868, astronomers observed the sun during an eclipse and saw the spectral fingerprint of hydrogen, as well as a second unknown element, assumed to be sodium.
When the French astronomer, Pierre Janssen, made his own observations during an eclipse in India, he found the yellow line didn't match up with the wavelength of sodium. He went ahead an invented the spectrohelioscope, allowing him to take repeat measurements without the need for an eclipse, and confirmed the spectral fingerprint of helium - not sodium - coming from the sun.
In the same year in England, the astronomer Joseph Lockyer was working on the very same incongruity, and came to the same conclusion that the second solar element was helium.
It was a complete fluke that their letters, which stated identical findings, reached the French Academy of Sciences within a couple of hours of each other.
The previously unknown (and allegedly purely extraterrestrial element) they discovered was named helium, after the Greek god of the sun, Helios.
Fellow scientists showed a healthy scepticism about the findings and gave Lockyer and Janssen a hard time about it. But by 1881, the mysterious element helium was discovered in lava thrown up by an erupting Mount Vesuvius and the scientists hurriedly moved on with their day.
Helium's Current Applications
Helium is mined from the Earth's crust for a range of applications.
It's lighter than air which makes it ideal for inflating air ships, blimps and balloons. This gives it a reputation for fun and games, however huffing on helium gas is ill-advised as it can cut off the oxygen supply to the brain, cause embolisms, and burst the lungs, causing haemorrhage (especially if taken direct from a pressurised tank).
Why does helium make your voice go high? Helium molecules have less mass than the oxygen and nitrogen found in the air, so sound waves can travel through them three times as fast. The sped-up frequency gives you the adorable voice of a chipmunk. The opposite effect can be produced by inhaling sulphur hexachloride which is denser than air.
A mixture of 8:2 helium and oxygen is used in the air tanks of deep sea divers and for people working under pressurised conditions. Helium-neon gas lasers are used to scan barcodes in supermarket checkouts. And the Large Hadron Collider in Switzerland uses helium to cool and strengthen its electromagnets to -271°C; these magnets keep the beams of particles on track as they race around the collision course at close to the speed of light.
A new use for helium is a helium-ion microscope (HIM) that gives better image resolution than even a scanning electron microscope (SEM).
It's also valuable as a recyclable cooling agent for super-magnets in MRI machines, and is used in space programs to displace liquid fuel in rocket tanks.
However, as a non-renewable resource we're due to run out of helium on Earth in the next two decades, and many of its medical and industrial applications have no viable alternatives.
Above: Comparison images of a 3D-fibrin matrix. For SEM, the fibrin matrix was coated with gold particles. In contrast for HIM imaging, no coating is necessary.
But here's the bright side. An estimated 25% of the universe is composed of helium, with around 1.1 million tonnes in shallow pockets just under the surface of the moon.
Unlike Earth, the moon lacks a protective magnetic field and has been bombarded with helium-3 solar winds for billions of years.
With the sufficient investment, many scientists believe we could tap into the vast quantities of extraterrestrial helium for use on Earth... as well as our not-so-distant colonisation of other planets.
Of all the elements, helium has the lowest boiling point of -269°C. Cooled a little more, liquid helium will climb the sides of a container and remain unmoving in a spinning container. It freezes at -272°C but requires 50,000 times the air pressure in your car tyres to do so.
Helium as an Energy Source
The real value of abundant helium is as a source of nuclear power.
Today, all commercial nuclear power plants use nuclear fission to split heavy isotopes like uranium or plutonium, which generates heat to be turned into electricity.
However, nuclear fission comes with its drawbacks: accidents like those at Three Mile Island (1979), Chernobyl (1986) and Fukushima (2011) reveal the serious and long term dangers of accidentally releasing large amounts of radiation into the environment.
The heavy elements required in nuclear fission are finite and non-renewable, and produce radioactive nuclear waste as a by-product. This is not a sustainable source of energy for humanity.
The dream of nuclear fusion has far greater appeal and is a serious area of research among many nations, some of which have banded together for an international solution.
As opposed to splitting heavy atoms, fusion combines light atoms in high energy collisions, releasing large amounts of energy as a result. Not only is it more efficient than fission, but it's sustainable and produces virtually no waste.
Most nuclear research is geared toward the fusion of hydrogen isotopes (namely deuterium and radioactive tritium) with the former being abundant in water and the latter produced by the neutron bombardment of lithium.
However, there is a cost to supply and the issue of radioactivity (albeit much less than the heavy radioactive isotopes of nuclear fission). The nuclear fusion scenario becomes even more attractive when you bring the light and non-radioactive isotope, helium-3, to the table.
The problems with the fusion of helium are two-fold.
First, getting two protons to fuse together (regardless of whether you're using hydrogen or helium isotopes) takes an awful lot of energy in the first place. It happens easily inside stars but then they are giant balls of gas burning at millions of degrees Celsius.
But physicists are making astonishing advances on this front.
In 2016, Germany switched on its Wendelstein 7-X stellarator for the first time, creating temperatures up to 80,000,000°C to generate hydrogen plasma. Further development is ongoing to create an environment for higher temperatures and longer discharges, to reach the goal of net power generation, making nuclear fusion a reality.
In 2017, construction of the multi-billion-dollar International Thermonuclear Experimental Reactor (ITER) in France reached the halfway point, on track for completion in 2025. ITER is a partnership of 35 countries which promises to be the first fusion device to create net energy.
The race is on.
Above: The International Thermonuclear Experimental Reactor (ITER) Nuclear Fusion Reactor
It's looking like nuclear fusion reactors are no longer an impossible dream. Now the only problem with the helium energy plan is sourcing the actual helium.
As we've seen, helium exists in massive quantities on the moon thanks to the helium-3-rich solar winds. The gas is laid down in the top few metres of the moon's surface, making it a relatively easy mining operation, if you overlook the bit about it taking place on the moon.
The helium could be extracted by heating the lunar dust to 600°C before bringing it back to Earth.
If achieved, experts reckon the lunar deposits alone could power the entire Earth for the next 200 years.
A fully-loaded space shuttle could carry 25 tonnes of helium, and could power the entire US for a year. This gives it a value of $3 billion per tonne and makes that whole moon-mining escapade look pretty appealing in economic terms, if not logistical ones.
And this is why helium could be our saviour. Granted, there are obstacles we need to overcome. But nothing worth having is necessarily easy.
China's Lunar Exploration Program, called Chang'e, will send astronauts to the moon by the early 2020s, which I don't need to remind you is only two years from now and not at all as distant as it sounds.
Chang'e will explore for rich helium-3 deposits and create a sustained human outpost for mining operations. Having a monopoly on such a resource would give China economic supremacy.
Now the helium rush is on. Russian, American and Indian scientists have urged the mining of the moon for helium-3, and numerous governments have teased the idea in the past, although with little actual progress to date. Perhaps the idea is simply too ambitious to attract serious funding given the incomplete status of nuclear fusion research.
Nonetheless, as debates on peak oil, resource depletion and climate change rage on, there has never been more urgency to find abundant clean energy sources.