Planets everywhere, and soon we'll have discovered thousands. Now there's a way to score their suitability for life, says astrobiologist Dirk Schulze-Makuch and his colleagues. Emily Lakdawalla previews 2012's solar system missions of exploration. Bill Nye is thrilled by new discoveries about our moon. What graffiti would you leave on the sands of Mars? That's the new contest from Bruce Betts and Mat Kaplan in What's Up!