Solar energy is increasingly popular as a home heating source. But only recently has it been seriously considered as a source of industrial power. NOVA looks at this new industrial approach, such as the use of a huge windmill in Ohio, giant machines that may generate electricity from the heat of the tropical seas or from the motion of waves, and an orbiting solar power station able to beam microwaves to earth.

NOVA traces 300 years of speculation, investigation and discovery that have centered on Mars—particularly the theory that the planet could support life. Questions raised by NASA's 1976 Viking mariner missions about how the vast canyons were formed are also explored.