Why people shouldn't go to Mars - yet
Following the moon landings in the 1960's, a manned mission to Mars seemed to some to be the obvious next step. But it didn't happen. Many people still hope for such a mission, but not me. Rather I believe we should take stock and ask what we really want to achieve.
Inspiration and the lack of it
On September 12th 1962 John F. Kennedy announced that the USA would send a man to the moon, and within 7 years they had done so. It was a huge undertaking, and must have used a significant amount of the nation's resources, but it was an achievement anyone would be proud to take part in. For thousands of years the moon had represented the unattainable, so its hardly surprising that there was a decision to go there as soon as the technology allowed it. There was the expectation that the space program would continue to expand, with manned missions to Mars and the other planets within a short time. However it was felt that the money being spent could be used for better things, and so the program was scaled back, using unmanned probes instead. But many people still yearn for the return of those days of human exploration, and from time to time the space program seems to be going back that way. However, I don't think that it will ever be the same again. The recent plan to return to the moon talked about doing it in 16 years. Seemingly its not just a case of quickly redoing what we already have the technology for - this is more than twice as long as the original moon mission schedule! Talk of using the space-station or the moon as a 'stepping-stone' for further travel is really a red herring - if you want to go somewhere, then you plan a mission to go there, not somewhere else instead. I don't see such missions as being an inspiration in the same way as those of the 1960's.
The most important question which people want answered from a trip to Mars is 'Is there life there'. If life is found then we also want to know how similar it is to life on Earth. Is it too based on DNA, with similar code for translating DNA bases into proteins. This would imply a common origin. Or does it use some totally different system for storing the information specifying the organism. In this case we would have a independent example of life arising, which would be hugely useful in testing ideas concerning the origin of life. Now sending humans to search for life rather than robots would have many advantages. We are better at spotting the places where the organisms may be living, and much more flexible in carrying out the analysis. However there is one big problem. If we did find DNA which was like ours then there would always be the suspicion that we took it with us - that the samples had become contaminated. With robots its much easier to avoid this. Also the abilities of robots will continue to improve and so I would think that a robot could do the job at a fraction of the cost of sending humans to Mars.
My main reason for not wanting manned missions is that there are plenty of unmanned missions on the drawing board which really have the potential to advance our knowledge, which seem much better candidates for space expenditure. There's the James' Webb Space Telescope (the successor to the HST), but the power of a telescope is limited by its size, and it hard to get a really big telescope into orbit. In radio astronomy a technique called interferometry is used using several telescopes spaced out to simulate one of much greater diameter. Doing this is trickier in infra-red and optical wavelengths - the telescopes positions have to be known to a precision better than the wavelength being observed, which is a fraction of a millimeter. But it's worth doing as it allows unprecedented resolution for the simulated telescope. In the case of the DARWIN mission, this will be used to investigate planets around other stars and specifically the atmospheres of such planets, telling us whether there may be life there.
Interferometry is so sensitive to small changes in separation that in the case of LISA it is used to detect precisely these changes. This is the Laser Interferometry Space Antenna, and the changes it detects will allow the detection of gravitational waves, and so study violent events elsewhere in the universe, such as the mergers of black holes, as well as testing the general theory of relativity which predicts such waves.
There is one manned mission I'd like to see though, which is related to the above. This isn't sending a person anywhere specific, its more to do with getting away from everyone else on Earth. Quantum theory predicts that for certain systems the results of measurements at two different detectors are correlated in such a way to suggest a connection, even though its impossible for a signal to travel between them. This has been confirmed by experiment, but to fully test it needs two human experimenters independently deciding on the measurement to be made at each detector. These would need to be about half a light-minute, or ten million kilometres apart, which means that at least one would need to be in space. But I think it would be worth it, not only for the testing of quantum theory, but for the issues of free will it looks at.
And the future...
To me the above is all much more exciting that sending someone to plant a flag on Mars. So am I against any more human exploration of space. No, I believe that new technology will lead to a much cheaper method of space travel within the next 40 to 50 years. Many of the readers of this website will still be around then, especially considering the improvements in medical technology we can expect. Then a more reasonable number people can visit the planets, and perhaps even go to the stars in the way we hear of in science fiction. In conclusion, I would say that your best bet for going into space yourself is to push forward the basic physics that is being done here on Earth.