A Salty Sea on Mars

Mars Exploration Rover Opportunity has returned conclusive evidence that water once flowed over the Meridiani Planum. The probe's Microscopic Imager had a big part in this discovery. We talk with the lead scientist for the MI Ken Herkenhoff. Emily Lakdawalla wonders if night ever comes to people living in a double star system, and Bruce Betts gets his whole family in on the fun during this week's What's Up!