As the astronauts flying on NASA's final space shuttle mission prepare for their return to Earth tomorrow (July 21), they took a moment to pay tribute to another historic space milestone: the 42nd anniversary of the first Apollo moon landing.
On July 20, 1969, Apollo 11 astronaut Neil Armstrong became the first man to step foot on the lunar surface, followed by Lunar Module pilot Buzz Aldrin.
"Forty-two years today, Neil Armstrong walked on the moon," Atlantis' commander Chris Ferguson radioed to Mission Control at the Johnson Space Center in Houston. "I consider myself fortunate that I was there to actually remember the event. I think there was probably a lot of folks in that room who didn't have that privilege or honor." [Giant Leaps: Top Milestones of Human Spaceflight]
"It's kind of interesting to be here on the final night of a shuttle mission. We don’t quite know what to think, we're just trying to take it all in," Ferguson said just before the his crew's sleep period.
NASA's Apollo moon program was sparked by President John F. Kennedy's compelling speech in 1961 that challenged the nation to put a man on the moon and return him safely to Earth before the end of the 1960s.
The dramatic events of July 20, 1969 achieved Kennedy's goal, and over the course of the Apollo program, five subsequent missions eventually landed astronauts on the lunar surface. In total, 12 ambassadors have had the unique privilege of leaving their boot prints on a world beyond Earth.
The last Apollo moon mission, Apollo 17, launched in December 1972, and the program officially ended in 1975.
Ferguson and his crewmates, pilot Doug Hurley and mission specialists Sandra Magnus and Rex Walheim, launched on the final mission of NASA's space shuttle program on July 8. Atlantis and its crewmates delivered critical supplies and hardware during its 13-day mission to the International Space Station.
Atlantis is scheduled to land on Thursday (July 21) at 5:56 a.m. EDT (0956 GMT).
After 30 years of flying the shuttles, NASA is retiring its three-orbiter fleet to focus on deep-space exploration missions to destinations like an asteroid and Mars.
You can follow SPACE.com Staff Writer Denise Chow on Twitter @denisechow. SPACE.com Senior Writer Clara Moskowitz (@ClaraMoskowitz) contributed to this report. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.