Dr. James Tuttle Keane discusses why Pluto probably has a huge underground ocean. To make this discovery, he used images of Pluto taken by the New Horizons spacecraft, computer simulations, and good old-fashioned pen and paper.
Dr. Barbara Cohen returns to the show to talk about meteorite collecting in Antarctica. These trips, which involve weeks of camping on the ice, provide invaluable scientific samples. She talks about what it's like to search for the rocks that "don't belong" in the frozen desert.