We'd never found a good way to do it. Porous rock is an excellent thermal insulator, so electric heaters don't work. Injecting steam-a technique sometimes used in conventional wells to make heavy crude oil and bitumen less gloopy-can heat up a section of rock but won't work past obstructions. The best option could be to lower a high-power, 2.45-gigahertze emitter-essentially a supercharged microwave oven-into the ground.