The Helium Conundrum (1)
Hint: The substance I’m referring to is produced in the Sun and other stars, as well as in Earth’s interior. Geologically, it is associated with natural gas, but costs 40 times more commercially.
The answer, if you haven’t guessed, is “helium”—family-head of the noble gasses, among which are also neon, krypton, argon, xenon and radon.
Despite its distinguished chemical lineage though, “helium” is hardly a household word. Poets and lyricists have left it for columns like this one. Nor are the ins-and-outs of “He-3” or “He-4” debated in pubs, or other public places.
But helium’s profile, in international discourse, is rising: Due in no small way, to a deepening production crisis, a spiraling political and economic conundrum that is ensnaring policy makers in both industrialized and developing nations.
Increasingly, this unsung industrial resource is inducing anxiety, because some scientists believe planetary reserves will have exhausted in 25 to 30 years—disrupting helium-dependent industries and professions, such as space, medicine, metallurgy, health and lighter-than-air flight.
A countervailing contention though, is that Earth’s reserves are quite adequate, if only world helium policy was more rational. Exponents point to large deposits of helium-rich natural gas in Russia, Poland, China, the Middle East, Africa and North America.
The conundrum stems partly from contrasting cosmic and terrestrial abundances. Helium is at once the second most plentiful element in the universe, after hydrogen—and one of the scarcest material substances on Earth.
Cosmically, helium makes up 23 to 25 percent of normal matter. All but a tiny portion of this is primordial, having been synthesized during the first few minutes after the Big Bang conflagration, 13.8 billion year ago.
The rest (one per cent or so) is the result of nuclear fusion in main sequence stars, like our Sun. Stars generate the energy our eyes sense as “light,” by combining four hydrogen nuclei into a nucleus of helium—two protons and two neutrons.
Earth contains no cosmic helium. Over the past 4.6 billion years, all has drifted off into space. Helium being “2” on the periodic table, only one substance is lighter—hydrogen. Helium thus finds it easy, to escape Earth’s gravity.
What is more, the element’s two protons and two neutrons actually occupy less space than a normal hydrogen atom—which has only one proton and an electron. Consequently, helium atoms can squeeze through openings in rocks that are too tight, even for hydrogen! So they seep to the surface and rise.
Where, then, does the helium associated with natural gas come from? Geologists and geochemists believe present terrestrial stocks formed over many millions of years, deep in Earth’s mantle, through a process called radioactive decay.
“Radioactive decay” occurs when an isotope (neutron configuration) of a particular element, has an unstable nucleus. Such nuclei seek stability by spontaneously transforming themselves. In this case, thorium-232 and uranium-238 (primarily) radiate “alpha particles”—another name for helium nuclei.
“Most of the helium that is removed from natural gas,” writes Hobart King, in Geology.Com, “is thought to form from the radioactive decay of uranium and thorium in granitoid rocks of Earth’s continental crust. As a very light gas it is buoyant and seeks to move upward as soon as it forms.
“When it… starts moving upward,” King continues, “it can fit through very small pore spaces within the rocks. Halite and anhydrite are the only sedimentary rocks that can block the upward migration of helium atoms. Shales [are]… a less effective barrier”. *To be continued.