NASA Administrator Charles Bolden listens as Mercury astronaut John Glenn speaks to employees during the 50 Years of Americans in Orbit presentation.

NASA Administrator Charles Bolden, right, listens as Mercury astronaut John Glenn speaks to employees during the "50 Years of Americans in Orbit" presentation at NASA's Kennedy Space Center in Florida.

This year marks 50 years since Glenn and Carpenter became the first two Americans to orbit Earth. Photo credit: NASA/Kim Shiflett