Mining the Oort — Frederik Pohl

Mars was harsh and unforgiving, but for the colonists who called it home, its future was as bright as the comets that hung in the night sky, for locked in those icy bodies were the water and gases that would make Mars live again, mined from the vast Oort Cloud beyond Pluto. Young Dekker DeWoe yearned to become an Oort miner. But when he finally arrived on Earth to begin training, the mining project was abruptly canceled. Then he began to hear rumors of a plan to force the restoration of the mining -- a plan that would result in the deaths of millions . . .