Apollo astronauts from left Jim Lovell Buzz Aldrin and Mike Collins pause during their tour of Launch Pad 39B.

At the Kennedy Space Center in Florida, Apollo astronauts, from left, Jim Lovell, Buzz Aldrin and Mike Collins pause during their tour of Launch Pad 39B for a group portrait. The pad is being modified to support the agency's new Orion spacecraft which will lift off atop the Space Launch System rocket. Orion is designed to take humans farther than they’ve ever gone before, serving as the exploration vehicle that will carry astronauts to deep space and sustain the crew during travel to destinations such as an asteroid or Mars.

The visit of the former astronauts was part of NASA's 45th anniversary celebration of the Apollo 11 moon landing. As the world watched, Neil Armstrong and Aldrin landed in the moon's Sea of Tranquility aboard the lunar module Eagle on July 20, 1969. Meanwhile, crewmate Collins orbited above in the command module Columbia. For more, visit http://www.nasa.gov/press/2014/july/nasa-honors-historic-first-moon-landing-eyes-first-mars-mission. Photo credit: NASA/Kim Shiflett