A pilot aboard the 1969 Apollo 12 mission to the moon has revealed what he knows about aliens.

In an interview,  Alan Bean, one of the 12 people who have successfully set foot on the moon, said he is convinced that aliens do exist, but he does not believe that anyone from the outer space has ever visited the Earth.

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Bean, now 85, argued that if they had, they would have made contact and announced their arrival and shared high-tech innovations.

"One of the reasons I don't believe they have been here is that civilisations that are more advanced are more altruistic and friendly - like Earth, which is better than it used to be - so they would have landed and said 'we come in peace and we know from our studies you have cancer that kills people, we solved that problem 50 years ago, here's the gadget we put on a person's chest that will cure it, we will show you how to make it'," he said. 

Bean said that people on Earth would probably do so when given the chance to go to another star and see a planet, say 1000 years from now, as he assumed a cure for cancer would have been discovered by then.

The former astronaut believes that life also exists on other planets by saying "There's so many billions of stars and these stars have planets around them so there must be statistically many planets around many stars that have formed life."

Bean has been in space for 1,671 hours and 45 minutes. Over 10 hours of that were spent on the moon and in Earth's orbit

Stephen Hawking, one of the world's most celebrated scientists, meanwhile, does not believe that aliens are intelligent or even particularly dangerous.

He said that if humans ever came into contact with aliens, they would probably fear for us and not the other way around.