In 1972, astronaut Harrison Schmitt scooped moon rocks into a bag for the ride back to Earth on Apollo 17. Along with those rocks, the bag contained a light helium isotope called helium-3. Some researchers think helium-3 could end the world's reliance on fossil fuels.

Abundance

Helium is made in the sun. When cosmic rays knock out a neutron, helium-3 is formed. Earth's magnetic field draws helium-3 to the moon, which means a large amount has formed on the moon's surface. Helium-3 exists in small quantities on Earth as the result of nuclear weapons maintenance.

Cheap Fusion

Combined with another isotope called deuterium, helium-3 would make fusion reactors less expensive than tritium-powered ones, since it eliminates the need for magnets.

Fossil Fuel Alternative

Mining helium-3 and bringing it back to Earth would be expensive, but it converts to electricity easily and would produce mass quantities of power, making it a great return on the investment. Harrison Schmitt estimates that five 1,000-megawatt helium-3 power plants would recoup the cost.

Cheaper Plants

Operating costs would be lower at fusion power plants because of the simpler technology of the reactors. Since the reactors produce no radioactive waste, plants would not have to pay for waste disposal. Helium-3 also would not pollute the air or water.

Moon Settlement

Mining lunar helium-3 would make moon settlement feasible and attractive. Power would never be an issue and mining would create byproducts useful for living there.

Source:

Popular Mechanics: Mining the Moon

Artemis Project: Lunar Helium-3