Encased in ice-cooled orange suits, scientists explore the Cave of Crystals, discovered a thousand feet (304 meters) below Naica (map), Mexico, in 2000.Expeditions in 2008 and 2009 uncovered biological mysteries, parallels with other planets, and the "Ice Palace," an unexplored cavern lined with rare crystal formations, according to Into the Lost Crystal Caves, a National Geographic Channel documentary to premiere Sunday. (The National Geographic Channel is part-owned by the National Geographic Society, which owns National Geographic News.)