US astronaut Buzz Aldrin salutes the American flag on the lunar surface.NASA/public domain

Buzz Aldrin, the second man ever to set foot on the moon, has taken part in a reddit AMA ahead of the 45th anniversary of the Apollo 11 landing on 20 July.

Aldrin, who planted his feet on the lunar surface within minutes of Neil Armstrong, answered questions about the 1969 mission, as well as future expeditions to Mars and what he thought about last year's Oscar-winning movie Gravity.

On Mars

Speaking about the possibility of humans landing on Mars, Aldrin said there is "very little doubt" in his mind that humans will visit Mars, and that he thinks it will happen in the next 20 years.

He said the first people to visit, however, should not come back to Earth and instead set up a colony for later arrivals. "I know that many people don't feel that that should be done. Some people even consider it distinctly a suicide mission. Not me! Not at all.

"Because we will plan, we will construct from the moon of Mars, over a period of six to seven years, the landing of different objects at the landing site that will be brought together to form a complete Mars habitat and laboratory, similar to what has been done at the Moon."

Aldrin also said the mission should be a collective effort from countries across the world, rather than through a privately funded company, adding: "[Whoever achieves it] will be remembered throughout history, hundreds and thousands of years in the future of the history of humanity."

On Aliens

Aldrin was asked if he believes in aliens and if he saw any while on board the Apollo 11. He said he technically saw a UFO (unidentified flying object) en route to the moon but said it was the sun reflecting off one of four panels – he just did not know which, meaning it was "unidentified".

In terms of the possibility of alien life he said: "There may be aliens in our Milky Way galaxy, and there are billions of other galaxies. The probability is almost CERTAIN that there is life somewhere in space. It was not that remarkable, that special, that unusual, that life here on earth evolved gradually, slowly, to where we are today. But the distances involved in where some evidence of life may be, they may be hundreds of light years away."

On Gravity

Discussing the 2013 film Gravity, which saw Sandra Bullock and George Clooney stranded in space, Aldrin said he thought the depiction of people moving around space was the "best" he has ever seen. However, he observed a few pitfalls in the movie: "The free-falling, the actions that took place between two people, were very, I think, exaggerated, but probably bent the laws of physics. But to a person who's been in space, we would cringe looking at something that we hoped would NEVER, EVER Happen.

"It's very thrilling for the person who's never been there, because it portrays the hazards, the dangers that could come about if things begin to go wrong, and I think that as I came out of that movie, I said to myself and others, 'Sandra Bullock deserves an Oscar'."

Favourite ice cream

"COCONUT ICE CREAM."