With the first flights NASA's new Orion spacecraft set to take place over the next several years, new human voyages beyond low Earth orbit are set to inspire a new generation of America's children. To celestial bodies beckon: the Moon and Mars.
What is the rationale for making Mars a long-term target of human space exploration? The finding that microorganisms live on Mars, whether made by astronauts or by robot probes, would be one of the most important discoveries of this new century. By studying such microbes, if they exist and are recovered by astronauts, it could do as much for biology and medicine as the discovery of the workings of DNA has been doing for the last fifty years. This may lead to medical breakthroughs unimaginable today and for this reason, even while emphasizing human Mars exploration, we mustn't neglect to send probes to the outer Solar System, particularly to Jupiter's moon, Europa, which may be as good a candidate as Mars for harboring native life.
Ultimately, human missions may or may not be needed in the search for living microbes or fossils from past life on Mars; that is, from a scientific perspective automated probes and robots alone may make more sense until we know more. And in the case of Europa, we are not even close to thinking about how a human mission would ever be carried out. But there is another reason for humans to make a trip to Mars beyond the needs of the search for life and that is to bring humanity together in the context of a space mission that should not be pursued by only one nation.
The same may or may not be true of the Moon, since our interest in it relates not to any prospect of finding life, but as a source of desperately-needed energy. Going to the moon is in our national interest. As for Mars, however, going as part of a new space race would be a missed opportunity and a terrible mistake. It is time to start talking with Russia, Europe, and anyone else who may be interested, about going to Mars together, as Carl Sagan proposed two decades ago. It is time to create an international space agency that would manage the expedition. And it is time for an international treaty against the militarization of space, modeled on the Antarctica Treaty, as Al Gore once proposed.