Mankind has dreamed of mining asteroids ever since the 19th century sci-fi serial "Edison's Conquest of Mars," but it has only come within scientific reach very recently. Asteroids are rich in metals found only in scarce quantities on Earth. If scientists figure out a way to tow an asteroid into the orbit of the moon, they can effectively harvest millions of dollars worth of minerals from even relatively small asteroids.
Many of these rare earth metals are used in high-tech devices like cell phones, computers and medical-imaging equipment. Scientists predict that asteroid mining will help keep prices low on these devices, but several things must occur to make investment in this process worth it from a financial standpoint. These include building a lunar base where rocket launches and mineral processing can occur, a demonstrable method for tethering an asteroid and changing its course to stay in the moon's orbit, and a way to return these minerals back to Earth using cheap, efficient and reusable rockets. Until then, mining asteroids is still just a science-fiction fantasy.
Private space exploration companies, like SpaceX funded by the famed entrepreneur Elon Musk, are working together with NASA and billionaire investors of the Planetary Resources group to attempt the first harvesting of materials and metals from an asteroid called Bennu in 2018.