The idea of colonies of humans on the Moon or Mars lies not only between the pages of science fiction paperbacks.
NASA has been planning a lunar base since the 1960s.
Investment in the space shuttle program drew attention away from this goal, but interest has been revived.
In 1991, veteran astronauts described some likely scenarios.
Perhaps a lunar base would be used for training missions to Mars.
Or the focus may be on scientific study of the Moon itself, which would call for a different kind of base.
A scientific community could be up and running by the year 2015.
If the idea is to set up a permanent colony on the Moon, a self-sufficient community of some six astronauts could be started by 2010.
It is likely that the first person to set foot on Mars has already been born.
