The planet Mars may be around 250 million miles away, but getting there is the easy part.
That is the view of someone who knows a thing or two about space travel - Edwin "Buzz" Aldrin, who in 1969 became the second man to set foot on the moon.
The American astronaut believes that mankind could touch down on the red planet by 2040, and believes that the generation born around the year 2000 will be the first to make the journey.
Dr Aldrin, 86, believes that through international collaboration on Earth a human colony could be established on Mars.
Such an outpost would need people willing to stay there for long periods to set up a colony that could become self-sufficient, he said, and suggested that it would be necessary to use Earth's own moon and that of Mars as staging posts.
It would also require a constant "cyclical" transportation to get people and supplies from the Earth to Mars.
But getting to the planet itself would not be so difficult, he believes.
"That is the easy part", Dr Aldrin said. "We know how to do that, we know how to get people there. It is being able to sustain yourself.
"(Getting there) is very realistic, in my mind."
Speaking at the Science Museum in London, Dr Aldrin said that focusing man's attentions on the moon would be to regress to 50 years ago, when he and Neil Armstrong first stepped on the moon as part of the Apollo 11 mission.
But a journey to Mars would break new ground. He said: "To take the step, to take the movement, to take the action to begin to occupy ... is there anything bigger that humans could do on Earth than to leave and begin to occupy?"