Over a billion miles from the sun, beyond the rocky inner planets and the gas giants, lie the ice words—Uranus and Neptune. NOVA takes you inside the missions that rewrote the story of the outer solar system: NASA’s Voyager 1 & 2 capture Neptune’s supersonic winds, and rings around a tipped-over Uranus. And when New Horizons flies by Pluto in 2015, it reveals jagged ice mountains and an underground ocean.

• Konstantin Batygin
• David Grinspoon