Environmental lawyers around the world have successfully made the case that rivers have rights, a movement that renowned science writer Dr. Robert Macfarlane tracks in his new book, 'Is a River Alive?'. Macfarlane takes us to some of the world's most beautiful rivers, and asks: what is it about running water that we find so compelling? And speaking of compelling, David Baron tells the story of how humans first become obsessed with the planet Mars. Was a 19th-century American's belief in Martians an accidental catalyst for modern space exploration?