NASA believes that a colony on Mars is a viable concept and one may be established within the next 25 years if certain technological problems are solved.
The main impediment is the cost of the projects that will allow the building of the colonies in the first place. There are also more practical challenges, like shielding humans from deadly radiation, preventing muscle degeneration and developing new and efficient constructing methods.
Since Mars is far away from Earth, the challenges that a colonization mission poses are not entirely known. Using the most advanced rockets that are currently available, an astronaut would need a minimum of nine months in order to reach the Red Giant. Studies have already showed that prolonged exposure to zero gravity may cause long lasting damage. One of the consequences affects the blood vessels in the retina. Under zero gravity they change their shape, a process that will lead to vision degradation. Since Mars only exerts one-third of the gravity that exists on Earth, the effects of a one-year mission to Mars may be quite severe.
Reducing the time it takes to reach Mars is the first step in order to prevent any unnecessary problems. Some argue that a nuclear propulsion system should be adapted for space use, in order to provide a continuous source of energy.
As technology evolves, many of the current problems may be solved in the future. For now, there no suitable shielding technology that can withstand radiation during extended exposure periods.
Searching for information
NASA will launch another rover to Mars in 2020. This rover will analyze the Martian environment in order to determine if the planet is indeed suitable for a future colony. Some experts argue that additional moon mission will allow us to refine our technologies in order to be prepared for the harsher conditions that are present on Mars.
What will happen in the future remains to be seen as SpaceX and Boeing are putting the finishing touches on bleeding-edge space shuttles.