The margin between success and failure in the exploration of outer space have been uneasily sharing the headlines during the past few days. A greater contrast could not be imagined: a ten-year old semi-decrepit orbital shack where there are problems with the drains and the air, and the advanced and efficient Mars Pathfinder lander which seems as comfortable on the frigid surface of Mars as it does in the balmy climate of Southern California. But both are products of and affected by the same process: the exploration of space proceeds today in a economic and social environment which is hostile to it.

Recall that it is now almost forty years since the first human orbited the earth. What commentator from the 1960s would have imagined that in those forty years, with the exception of a brief foray to the Moon and back, the human exploration of space would be limited to repair missions in low earth orbit and (extremely boring) tests of endurance on a decade-old space station? After forty years there is still no permanent human presence beyond Earth's orbit and, with the exception of probes like the Sojourner rover, the solar system is still largely unexplored. The last landings on Mars were over twenty years ago. What happened?

A crisis faces science in our society today. The innate human desire to question to take risks and explore is challenged more and more often and with greater and greater vigour. The latest scientific discoveries are greeted not with acclaim and praise but with a raised finger and questions: 'Should we really be doing this? What are the consequences?', with no regard to the rewards they might bring. The need for certainty and freedom from doubt is incompatible with the practice of science and is indeed stagnating it.

At the Pathfinder news conferences, reporters continually focus on minor problems afflicting the mission rather than expressing interest in the wealth of scientific information flowing back from Mars. NASA officials state over and over again how inexpensive the project was - if only as much effort could be put into maximising scientific returns rather than keeping the costs down to that of a Hollywood feature film. Pathfinder is viewed differently from Mir only because it is a more successful adaptation to how the perception of risk and exploration has changed in society.

But the human exploration of space is a different matter - and one which is much more susceptible to today's uncertain mood and much less capable of adapting to it. It is a risky and extremely dangerous venture; that is why it is a frontier. It is also an activity where the potential rewards are much higher. By exploring the frontier of space and testing our abilities in extreme situations our ability to solve problems and cope with adversity in much less hazardous terrestrial environments is immeasurably improved. But instead economic analyses dominate all discussions and remain the primary factory in deciding whether or not any particular activity is carried out - regardless of its scientific benefits or intrinsic worth. And no specific, tangible and immediate economic benefits can be offered as a means to extend political vision beyond the surface of Earth.

Many commentators have taken the recent Mir accident as an opportunity to criticise the Russian space programme, using much the same rhetoric that was used ten years ago in the days of the Cold War. But it does well to remember that the Americans have not had a space station since the Skylab mission of the 1970s and that the Space Shuttle has not delivered anywhere near the number of launches which were planned - travelling into space has never become the routine matter which it was promised to become. In the aftermath of the failed Bush Space Exploration Initiative, the manned exploration of space has become, in the words of one commentator 'no longer politically correct'. But the manned exploration of space offers many returns which will never be fulfilled by robotic probes like Pathfinder. Human ingenuity and creativity can only be partially replicated on the surface of Mars by a robot probe 120 million miles from its controllers. To fully understand Mars, its geological and biological history, will require more than unmanned missions.

To venture into space we must be strong willed and determined. We must be fully committed to its exploration and discovery; space permits no half measures and is unforgiving of mistakes. But we will be well rewarded for the risks we take.