President Trump issued an executive order last month allowing US companies to mine the moon, but—is this really possible? Sure enough, Popular Mechanics lays out enough of the science, current projects, and history of moon-mining enthusiasm to make it seem real. "We've just been moving in a circle for a long time," says George Sowers, a space-mining researcher. The story goes back at least to the Outer Space Treaty of 1967, which allowed for off-world commercialization but not sovereignty; the Obama administration updated it in 2015 to let Americans own and sell anything gathered off the planet. The moon's bounty includes an apparently healthy supply of oxygen and hydrogen, "the most efficient chemical propellants known," says Sowers. "You have rocket fuel."
That could turn the moon into an outpost for colonizing Mars, if miners harvest enough water from the lunar ice lurking in deep craters. But how to properly heat up that ice? Ideas range from mirrors to nuclear-powered thermal mining—and yes, there are small uranium reactors that could go to the moon—or, as a baby step, sifting the ice in shallow craters, which would extract fewer resources at lower cost. On the plus side, NASA is sending up small, exploratory rover missions to cull samples and map the moon's water resources. But it's not all rosy: The Guardian reported last year that some scientists are worried we'll mine moons and planets before Earth enters a crisis phase in which it lacks needed resources. "Once you've exploited the solar system, there's nowhere left to go," says an astrophysicist. (Read more moon stories.)