COLOMBO, Sri Lanka (Reuters) -- With guided tours of outer space set to become a tourist attraction, space exploration will soon be driven more by commercialism than scientific curiosity, a U.S. astronaut said on Sunday.

Buzz Aldrin, the second man to set foot on the Moon, and science-fiction writer Arthur C. Clarke met in Sri Lanka to discuss their vision of the future of space travel.

"The immediate future of space travel depends on the ability of private citizens to get into space as paying tourists,'' Aldrin told a news conference after the meeting.

Clarke, 83, was internationally acclaimed as a space visionary in 1945 for his controversial theory forecasting a world linked up by a network of geostationary satellites. He said space tourism would be the "next big leisure activity of our species.''

Aldrin said cheaper, reusable rockets would be needed.

"We will soon have cheaper, safer rockets that can be used again and again to cater to...tourists,'' he said.

Both men agreed the benefits of commercial space travel would be more than just financial.

"Space tourism is the only way to build the space generation that will take us...to Mars and beyond,'' said Aldrin.

The British-born Clarke, who has lived in Sri Lanka for 40 years, said colonizing other planets was the only way for the human race to survive a collision between Earth and a big meteorite.