Neil Armstrong's step marks for many mankind's greatest technological achievement.

The Apollo 11 mission was achieved by the collaboration of 400,000 people in the US space programme and cost $25bn.

But the anniversary has brought not just new details of the Moon landings but sadness that this first step into space was not followed by others.

John Andrew reports: "500 million viewers watched in amazement"

Edwin "Buzz" Aldrin, the second man on the Moon, puts it this way: "So titanic was that achievement and yet so timid our subsequent efforts."

Mr Aldrin said history would record the 20th century as the time when humans went from the Wright brothers' first powered flight to the moon in 66 years, only to languish in "low Earth orbit" for the next three decades.

The lander touched down with only 17 seconds of fuel left

"Humans must follow robots to the far reaches of the solar system and ... space must be made accessible, not just to scientists and engineers but to journalists, teachers, poets and all the people of the earth," he said.

The Apollo astronauts, now in their 60s and 70s, have publicly lamented the failure to establish a colony on the Moon and send an astronaut to Mars. They have issued fresh calls for such missions.

"Man can successfully travel to another planet ... but he cannot live in the past," said George Mueller, who as Nasa's associate administrator of manned space flight for much of the 1960s directed the Apollo programme

He looks back with mixed emotions. "I remember it being a great achievement. I also remember a disappointment that the political situation was such that we didn't continue the exploration of the moon and beyond."

BBC Science's Richard Hollingham talks about the technology that took man to the Moon

However, the anniversary comes at a time when interest in space exploration is again growing. This time businesses, not governments, are looking to space, hoping to exploit opportunities for satellite launches and space tourism. Last year private investment in the space industry exceeded public investment for the first time.

A unique view of Earth

Nasa will mark the moon landing anniversary on Tuesday with the launch of shuttle Columbia on a mission to deploy a 25-tonne X-ray telescope in space. The mission will be led by Eileen Collins, the first woman to command an astronaut crew.

The new revelations about Apollo 11 have included the fact that if Armstrong and Aldrin had been stranded on the Moon, their communications systems would have been turned off, leaving them to die in silence.

Also revealed is the truth about what Armstrong said when he put his foot on the Moon, one of the most famous quotes of all time.

Listening to the recording it sounds like: "That's one small step for man - one giant leap for mankind." But for years later the official transcript of the mission added an "a" before "man".

Astronomer, Patrick Moore talking to BBC Breakfast News

Now the mystery of what he did say has been solved and by the only person who really knows the answer. Armstrong has admitted he got his lines wrong.

In an extremely rare public appearance last Friday, he set the record straight.

Before the mission his wife helped him with the choice of words. As he stepped off the lander's footpad he wanted to say "a small step for a man, a giant leap for mankind", and that is what he thought he did say. But after listening carefully to recordings of his words he now admits that he forgot the "a".