In the early years of the 20th century, zeppelins filled with flammable and explosive hydrogen were all the rage in Germany, a reckless infatuation that ended with the eruption and crash of the Hindenburg in 1937. Sometimes, technology is a triumph of wild-eyed enthusiasm over the unpleasant facts of the real world. Today we are witnessing a similar outburst of enthusiasm over the literally outlandish notion that in the relatively near future, some of us are going to be living, working, thriving and dying on Mars ... Unfortunately, this Mars mania reflects an excessively optimistic view of what it actually...