Astronomer Phil Plait introduces his new book "Under Alien Skies." Plait has worked as part of the Hubble Space Telescope team as well and is a public outreach advocate for NASA missions. He has an upcoming talk at Clark Planetarium in Salt Lake City. (1:10)Then, when you think of NASA, you may think of mighty rockets, rovers and astronauts. What you may not know is that NASA is the home to the largest group of Earth scientists in the world, including NASA climate scientist Dr. Lesley Ott. (27:33)