Exploring The Mystery of Dark Matter with Richard Massey

How are we finding and even mapping dark matter when it can't be seen? CalTech's Richard Massey is one of the researchers who has learned how to map the mysterious material that dominates the universe. He comments on the recent discovery of a ring of dark matter. Emily Lakdawalla's Q&A closes in on Mercury with the MESSENGER spacecraft, while Bruce Betts and Mat Kaplan explore the night sky and announce a new space trivia contest in What's Up.