Balloon sellers, power plants, doctors, deep-sea divers, and astronauts depend on it. So crucial is the rare gas helium in a range of energy, science, and engineering applications. India is now one of the few countries with the expertise to extract helium from natural gas. The ONGC, Saha Institute of Nuclear Physics and the Variable Energy Cyclotron Centre, Kolkata, and the Department of Science and Technology have jointly set up a pilot plant for this in Tamil Nadu.
Discovered in 1868 by British scientists, helium is found in natural gas deposits, and in the atmosphere where it accumulated over billions of years by the decay of uranium and thorium. Helium is inert (not chemically reactive with other elements or compounds), odourless, tasteless, and the lightest gas after hydrogen. Unlike hydrogen, however, it is non-flammable. This makes it ideal for use in weather balloons and — in its liquid state — as a cryogenic refrigerant for medical and industrial research. It eases breathing difficulties in asthmatic patients and deep-sea divers coming out of water. It cools the superconducting magnets in MRI scanners, nuclear fusion power plants, and electric systems, and Nasa uses it to pressurise space shuttle fuel tanks.
Although helium is the second most abundant element in the universe, on Earth we are fast running out of it. A by-product of fossil fuel extraction, helium is lighter than air and bubbles irrecoverably into the atmosphere. So its best source is extraterrestrial. At 93 million miles away, the sun is a wonderful, if inaccessible, helium factory. When the solar wind — the stream of charged particles emitted by the sun — strikes the moon, however, helium 3 is deposited in its powdery soil. Over billions of years, meteorite bombardment dispersed more than a million tons of helium 3 throughout the lunar surface. This is enough to power the world for thousands of years. The logistics of heating lunar soil to nearly 1000 C to liberate the gas and transporting it to Earth are daunting. But the moon would be a stepping-stone to other helium 3-rich sources like the atmospheres of Saturn, Uranus and Neptune.