NASA Administrator Charles Bolden answers social media attendees questions from just outside the launch pad where the United Launch Alliance Delta II rocket with the Orbiting Carbon Observatory-2 (OCO-2) satellite onboard sits ready to launch, Monday, June 30, 2014, Space Launch Complex 2 Vandenberg Air Force Base, Calif. OCO-2 will measure the global distribution of carbon dioxide, the leading human-produced greenhouse gas driving changes in Earth’s climate. OCO-2 is set for a July 1, 2014 launch. Photo Credit: (NASA/Bill Ingalls)