Since the time of Aristotle, humans have wondered, "Are we alone?" The concluding hour tracks the accelerating search for planets and the presence of life beyond the solar system. Acclaimed planet hunters Geoff Marcy and Paul Butler examine what they believe is a previously undiscovered solar system and identify planets that appear cool enough to support water and possibly life. The program also explores the latest efforts in the search for extraterrestrial intelligence and goes behind the scenes as scientists prepare to look for evidence of primitive life on Mars through missions such as Pathfinder. Mysteries of Deep Space, a series of three one-hour programs, dives into the vastness of space as it presents the bold achievements of modern astronomy, joining astronomers as they probe the limits of the observable universe and peer into the violent worlds of black holes and supernovas.