STS-125 Tweetup

NASA Astronaut Mike Massimino, known as "Astro_Mike" on Twitter, answers a question during a presentation with fellow STS-125 shuttle mission crew members at the NASA Tweetup event held at NASA Headquarters, July 21, 2009 in Washington. Nearly 200 of NASA’s Twitter followers are in attendance. Photo Credit: (Carla Cioffi)