Airs Tuesdays at 9pm/8c on HISTORY. On alien planets, they rain from the sky as scalding iron. On distant moons, even at hundreds of degrees below zero, they slosh around in pristine lakes of methane. They can cover entire planets in miles-deep oceans of electrified hydrogen metal. Or erupt on alien worlds through miles-high geysers. They churn in the interiors of dead stars and even our own planet. Theyre so rare in the universe, they almost dont exist, but these are the magical liquids of our Liquid Universe. Visit the official fan page at http://facebook.com/TheUniverse, follow HISTORY on Twitter at http://twitter.com/History_Daily and visit the official website at http://history.com/theuniverse.