In an action-packed day and a half, NASA's Cassini spacecraft will be making its closest swoop over the surface of Saturn's moon Dione and scrutinizing the atmosphere of Titan, Saturn's largest moon. The closest approach to Dione, about 61 miles (99 kilometers) above the surface, will take place at about 1:39 a.m. PST (4:39 a.m. EST) on Dec. 12. One of the questions Cassini scientists will be asking during this flyby is whether Dione's surface shows any signs of activity. Understanding Dione's...
