[T]he rare earth elements perplex us in our researches, baffle us in our speculations, and haunt us in our very dreams. They stretch like an unknown sea before us mocking, mystifying and murmuring strange revelations and possibilities. William Crookes
Five centuries from now - barring unimaginable catastrophe - the moon will be developed real estate. There's economic incentive to exploit the moon - the helium-3 will be useful in powering fusion reactors, and the rare earth elements could supplant the limited terrestrial supply of these materials. Seth Shostak