Almost 85 years have passed since Edwin Hubble first categorized galactic shapes. Now we finally know why they form this way. Cal Tech cosmologist Andrew Benson takes us through his Galform computer model. Emily Lakdawalla explains how you can select a site on Mars to be imaged. Bill Nye reports from SpaceX with two special guests. It's a chilly night for What's Up with Bruce Betts and Mat Kaplan, but they'll still give away a signed copy of William Hartmann's Traveler's Guide to Mars" in the new space trivia contest."