The European Rosetta today became the first man made craft to start flying alongside a comet. Previous missions have only managed to pass comets at high speed. The unmanned Rosetta probe aims to orbit it for at least a year. Scientists are hoping Rosetta will “open up a treasure chest of discovery”. The BBC’s David Shukman was at mission control in Darmstadt in Germany, to witness this landmark moment in space exploration. Plus, closer to home, we’ve got some good tech news as well. We’re hearing that Yelp is leasing 50,000 square feet of Merchandise Mart, making it the latest in a string of tech companies setting up or expanding their work forces in Chicago. Crain’s real estate reporter, Ryan Ori, broke the story about Yelp coming to Merchandise Mart today and joins us to talk about the move.