Space travel to Mars is undoubtedly feasible, but the cost-benefit ratio in all regards is far too high to justify continued investment. We should not just consider whether it is too dangerous for our astronauts which it undoubtedly is but also for our money.
Exciting, titillating data is often returned by the unmanned landers to Mars. The potential to discover life, to test new remote technology, to push the boundaries of space travel these are all amazing accomplishment. But has any assessments been made of the benefits gained from these probes in terms of information and technology? Could similar benefits be derived from exploring the moon again, or using remote-sensing techniques that do not require expensive, ultimately disposable space craft? Is it worth millions of dollars for each successful mission if the potential for unsuccessful missions - including complete failure - has already been substantiated? The prospects for life on Mars are slim. Considering how difficult it is for organisms to be fossilized and preserved on Earth, how likely is it that we could find traces of life on Mars even if the exist?
The prospect of manned mission is also very exciting. It would be the furthest boundary of exploration and human adventure yet achieved. But again, what is the cost-benefit ratio of sending a manned mission to mars? Do we want to invest in sending people to Mars if the potential exists that all we will accomplish is building the universe's most expensive coffin? I'm old enough to have seen TWO space shuttle explode; the process of take off and re-entry on routine missions is obviously very dangerous. The infamous Apollo 13 mission illustrates that even what had become routine missions it was the 13th Apollo, after all can have unexpected and potentially disastrous problem. Do we as taxpayers want to assume the financial and ethical risk of failure, when similar technology could be applied to further moon missions? If a mission to Mars is successful, we will have accomplished a great feat of adventure, but not much more. If a mission fails, even one, we will have spent hundreds of millions of taxpayer dollars killing our brave and expensively trained astronauts.
Given these considerations, a mission to Mars should not be viewed in terms of absolute risk, but in terms the cost-benefit to successful mission, and the cost of an unsuccessful mission. Given all the potential for things to go wrong between the 3rd and 4th planet from the sun, it is far to dangerous too invest our money and our talent astronauts on a fools errand to the Red Planet.