NASA astronaut Mike Massimino, far left, Sesame Street's Elmo and NASA astronaut Doug Wheelock, far right, speak at the STS-135 Tweetup, Thursday, July 7, 2011, at Kennedy Space Center in Cape Canaveral, Fla. Elmo asked the astronauts questions about living and working in space. 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)