Perhaps you might find it hard to swallow... that you're already eating/drinking recycled bodily wastes from dinosaurs and many other animals (including humans). (And there is no noticeable tang at all.)
Re: sigh - just use left handed sugar and be done with it
There are actually a few reasons why you can't just replace regular sugars with non-digestible isomers. The problem is that non-digestible sugars don't give you calories, but they're also *not* digestible -- so they act like laxatives. That's part of the reason why artificial sweeteners are usually hundreds of times as sweet as regular sugar -- so that they don't occupy so much volume in your digestive tract.
Mars actually has much less than "half" the amount of Earth's atmosphere, and there's some debate over the cause. Mars may have had a thicker atmosphere in the distant past, but it could have been stripped away by the solar wind. The Earth's atmosphere might be protected by the solar wind due to its strong magnetic field.... http://www.space.com/11187-earth-magnetic-field-solar-wind.html
As for the term "suicide mission" -- that can be debated endlessly until we see the actual viability of the technical specs of Mars One in 2020-something. (So far, I'm not convinced that Mars One will even have a reliable launch vehicle -- unless it purchases one from SpaceX/etc -- much less a viable spacecraft for a multi-week space journey.)
Sorry to disappoint you. I'm not going to argue with you about whether these links were about "energy-generating systems" or not. I suppose everyone can choose their words more carefully to be more accurate, and I did not in this post.
Thanks for taking the time to write a thoughtful comment.