It will dwarf all current optical instruments. GMT Director Patrick McCarthy describes the mammoth telescope project from his Pasadena base of operations. Emily Lakdawalla explains the bad case of acne on the face of Mars. Bill Nye says a solar sail could test a weird prediction by the theory of relativity. Bruce Betts joins Mat Kaplan immediately after the Planetary Society's open house for a look at the night sky. The boys also have Celestron astronomical binoculars to give away in the space trivia contest.