One day, a cosmic disaster will make life on Earth impossible. To survive, we must find a new home amongst the stars. Scientists are already developing new propulsion systems to take us to these distant worlds.

It's a voyage of exploration like no other - to Titan, Saturn's largest moon and thought to resemble our own early Earth. For a small team of British scientists this would be the culmination of a lifetime's endeavour - the flight alone, some 2 billion miles, would take a full seven years. This is the story of the space probe they built, the sacrifices they made and their hopes for the landing. Would their ambitions survive the descent into the unknown on Titan's surface?

Andrew Graham-Dixon continues his exploration of German art by looking at the tumultuous 19th and early 20th centuries, and how artists were at the forefront of Germany's drive to become a single nation. Andrew travels to the north and the coastal town of Griefswald, the birthplace of Caspar David Friedrich, the most influential of the German Romantics, to discover how the Baltic coast impacted his mysterious paintings of the German landscape. He also visits Berlin and explores the art of the powerful Prussian state, which would spearhead the unification of Germany in 1871. The episode ends with the outbreak of World War I and the attempts of the artists Franz Marc and Otto Dix to rationalise the catastrophic experiences of the world's first technological war, a war driven by the Prussian innovations.