The second part of Alex's views on travel to Mars:
Much like the interior of Antarctica, Mars remains inhospitable.
For humans to live on the planet for any significant period of time would require the recycling of water and air, along with other so-called "life systems".
At Concordia station in Antarctica (my current home) we use "grey water recycling" - taking the water generated from domestic activities such as laundry, bathing and dishwashing and recycling it on-site for other uses.This mirrors the system used on the International Space Station (ISS).
But there are even grander ideas that could further extend the duration of human habitation on Mars.