A mistake made during the Apollo 11 moon landing could have brought lunar germs to the Earth, astronauts have revealed.

When the three astronauts flew to the Moon and back, 50 years ago this month, Nasa worked hard to ensure that no bugs were brought back from the lunar surface.

All three of the Apollo 11 crew were put into special clothes, scrubbed down and taken to a quarantine facility where they lived until scientists could be sure the Earth would not be contaminated.

But interviews from a new documentary – filmed by PBS and revealed by Space.com – show that the plan to protect Earth could easily have failed, and that space bugs could have got into the Earth’s atmosphere despite Nasa’s best efforts.

The astronauts noted that Nasa did not think there would be anything alive on the Moon that could be brought back down to the Earth. But the precautions were taken in case there were.

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However, astronaut Michael Collins – who stayed in the command module during the time his crewmates Neil Armstrong and Buzz Aldrin were on the moon, but would have picked up any possible germs as soon as they climbed back in – noted that all of that hard work could have been undone as soon as they landed back down on Earth.

“Look at it this way,” he said. “Suppose there were germs on the moon. There are germs on the moon, we come back, the command module is full of lunar germs. The command module lands in the Pacific Ocean, and what do they do? Open the hatch. You got to open the hatch! All the damn germs come out!”

Buzz Aldrin made a similar point as footage showed the astronauts being disinfected as they were on a raft next to the spacecraft they’d splashed down to Earth on.

He said that the rescuers had cleaned him down with a rag – and then thrown that same rag straight into the water.