Best bet in the short term is asteroid mining. Some of the nickel-iron types have loads of valuable metals, the sort you might get if you could crack open a planet and get at the deep zones. You don't have to dig for it, just process it. All the solar power you need.

Ideally you would bring the asteroid into an Earth orbit, and then work on it. Easiest way to do this is start processing the asteroid, and fire the slag off as reaction mass. Would take years, but you could mine an object like that for years. See my (file no. 18 from the old board's gallery, not restored)

By the way, that would be a DISTANT Earth orbit, lunar or beyond. Or the L4 or L5 Lagrangian points (the others aren't stable). You think screwups are bad with nuclear plants, try screwups moving asteroids around.

Meanwhile, dig around on the Moon. Who knows what we'll find?