The entire crew of the Apollo 11 mission has made a rare public appearance in the United States to celebrate the 40th anniversary of the historic landing on the moon.
The American crew became the first to accomplish the dream of ages and walk on the lunar surface.
"That's one small step for man, one giant leap for mankind," said astronaut Neil Armstrong as he stepped down from the lander on 20 July 1969 as an estimated 500 million people on Earth crowded round televisions and radios.
At the United States Air and Space Museum in Washington, Mr Armstrong, the first man to set foot on the moon, said the race to get there had been the ultimate peaceful contest and it was an "exceptional national investment" for the United States and the former USSR.
"I'll not assert that it was a diversion which prevented a war, nevertheless it was a diversion.
"Eventually, it provided a mechanism for engendering co-operation between former adversaries. In that sense, among others, it was an exceptional national investment for both sides."
The commemoration was the first of a series for the week marking the anniversary, which also includes a reception at White House hosted by President Barack Obama.
Other celebrations will be held from the Kennedy Space Centre at Cape Canaveral, Florida, where the Apollo 11 mission blasted off, to mission control at the Johnson Space Centre in Houston, Texas.
Time to explore Mars, says Aldrin
The mission's engineer and the second person to walk on the lunar surface, Buzz Aldrin called for renewed efforts to send a manned mission to Mars.
"Apollo 11 is a symbol of what a great nation and a great people can do if we work hard, work together and have strong leaders with vision and determination.
"The best way to honour and remember all those who were part of the Apollo programme is to follow in our footsteps; to boldly go again on a new mission of exploration."
Apollo 11 member Michael Collins, who circled the moon alone while Mr Armstrong and Mr Aldrin walked on it, said Mars was more interesting than the moon and also urged further exploration of it.
"Sometimes I think I flew to the wrong place. Mars was always my favourite as a kid and it still is today."
The US space agency NASA's currently stated aim is to return astronauts to the Moon by 2020. But that vision is under review, along with the space vehicles that would get them there.
NASA is due to retire its space shuttles next year and replace them with the Orion spacecraft, an Apollo-like capsule that would launch on a new rocket called Ares 1.