Tracy Thumm, left, and Justin Kugler both from the International Space Station Program Science Office at Johnson Space Center speak at the STS-135 Tweetup, Thursday, July 7, 2011, at Kennedy Space Center in Cape Canaveral, Fla. About 150 NASA Twitter followers attended the event. The STS-135 mission will be NASA's last space shuttle launch. Photo Credit: (NASA/Paul E. Alers)