Before another century is done it will be hard for people to imagine a time when humanity was confined to one world, and it will seem to them incredible that there was ever anybody who doubted the value of space and wanted to turn his or her back on the Universe.
Remember this: once the human race is established on more than one planet and especially, in more than one solar system, there is no way now imaginable to kill off the human race.
The single simplest reason why human space flight is necessary is this, stated as plainly as possible: keeping all your breeding pairs in one place is a retarded way to run a species.
I believe that the long-term future of the human race must be space and that it represents an important life insurance for our future survival, as it could prevent the disappearance of humanity by colonizing other planets.
I agree, along with Carl Sagan, that we should eventually become a two planet species. Life is too precious to place on a single planet.
If our long-term survival is at stake, we have a basic responsibility to our species to venture to other worlds. Sailors on a becalmed sea, we sense the stirring of a breeze.
I suggest that going to Mars means permanence on the planet - a mission by which we are building up a confidence level to become a two-planet species.
I can't think that leaving Earth once is enough.
The human race shouldn't have all its eggs in one basket, or on one planet. Let's hope we can avoid dropping the basket until we have spread the load.
