It would be challenging for humans to live on Mars for a large number of reasons. Cabrol and Grin (2018) cite “low and widely varying temperature, low atmospheric pressure, low water activity, and high ultraviolet and ionizing radiation” as the primary causes of the planet’s inhospitality. To enable life on Mars, it would be necessary to establish an area with stable livable temperatures, a breathable atmosphere, and radiation protection. However, these are only the basic requirements that need to be supplemented with the necessities of life.
Relying on Earth for food would be inadvisable due to the difficulty and risks of delivering it, so the colony would have to learn ways to grow plants locally or produce it in other ways. Per Choi (2016), there is water on Mars, frozen on its polar caps and trapped in minerals, and it could be extracted from there. If a plant ecosystem were established, it could help produce oxygen, though it would likely have to be supplemented by technology. Lastly, energy could be created in numerous different ways, though nuclear appears the most feasible due to its longevity and efficiency.
In the case that humanity was to send a mission to Mars, extensive preparation would be necessary. For permanent habitation endeavors, a reusable spaceship such as that SpaceX is building (Wall, 2018) is essential. The settlers would bring a supply of food as well as the tools they need to establish a small self-sustaining colony. Depending on how potent these tools are, they could potentially stay indefinitely, though realistically, a period of a year or less is more likely. The advice that the author would give those departing was to focus on coming back, as others could continue where they left off on Mars while nobody could compensate for their death.
References
Cabrol, N. A., & Grin, E. A. (Eds.). (2018). From habitability to life on Mars. Elsevier Science.
Choi, C. Q. (2016). Water on Mars: The story so far. NASA. Web.
Wall, M. (2018). A base on Mars? It could happen by 2028, Elon Musk says. Space.com. Web.