Thousands of things could go wrong at any stage of the Mars Phoenix Lander's mission. But Peter Smith, the mission's Principal Investigator, says that the most nerve-wracking parts are getting Phoenix safely into space and back down again on Mars. Podcast produced by David Levin. Interview by Jonathan Grupper. NOVA is produced by WGBH in Boston. Funding for NOVA is provided by ExxonMobil, David H. Koch, the Howard Hughes Medical Institute, the Corporation for Public Broadcasting, and public television viewers. For more fun science stories, visit our website at pbs.org/nova/mars