NASA isn't too clear about what exactly it's hoping for private companies to do once they get to the moon. What exactly do they mean by commercial activities? How might companies make money by rocketing off to the moon? One possibility is mining – lunar soil is rich in rare earth elements that are in demand on our home planet, along with helium-3, which could be turned into a clean energy fuel for nuclear fusion. But Professor Ian Crawford of Birkbeck University, London, told BuzzFeed, "It can't be said that NASA are looking to mine the moon just yet."