One thing that keeps flitting into my head when we talk about a human mission to Mars, is the ethics of it. Right now we don't have the ability for anything but a one-way mission, and still I know there are people who would jump at the chance. I seem to recall reading that women astronauts are required to go on birth control, primarily to eliminate their periods, and this already seems like such an invasion of personal choice. Imagine a trip that takes 3 years each way. In a situation like this NASA really will have to take steps to prevent pregnancies, or to be able to deal with them should they happen.
The one aspect that popped into my head today though upon reading the above linked article by Buzz Aldrin is the issue of consent. The standard for experiments performed upon humans (and you can't call a trip to Mars anything but an experiment) is one of informed consent: the participants must be made aware of the risks (and the risks must be below a certain level), and the participants must give consent. Moreover, the participants have the right to with draw consent at any point in time. Missions on the ISS and such are already seriously pushing the boundaries on this one IMO (does the screening of astronauts beforehand allow NASA to get around the ethics board? or is NASA not subject to an ethics board?). How much more questionable in terms of withdrawing consent is a round trip to Mars? What about a colonization trip?
On the other hand, the worry about consent is another incentive for mandatory birth control and/or sterilization: children are unable to give consent, and it would be unethical to put an infant into the situation of a trip to Mars. I wonder at what point in colonization we will determine it is safe enough to allow children. And will the requirements be different for children transported to the colony vs. children produced in situ?