"The Next Prerogative for Colonization: Lunar Base or a Mars Habitat"," Several reasons are given for this ranging from the need to protect ourselves from nuclear annihilation (as stated by eminent scientists such as Stephen Hawking,) to creating an international cooperation environment for the various nations all across the world.
However, in order to accomplish this, first the proper strategy must be maintained for success.
In a way, this makes sense, since the moon has been studied completely by both manned missions as well as by probe missions.
Water is an important material, since it can be electrolyzed to produce hydrogen and oxygen separately.
On the other hand, oxygen is needed as an oxidizer for the fuel, as well as an element for breathing.
The existence of vacuum conditions, as well as the unavailability of atmosphere makes Moon a difficult place to expand.
The atmosphere of Mars is less than 1 percent dense, as compared to Earth's atmosphere, but it is still enough to diffuse the light and to provide at least some sort of protection against cosmic rays and other forms of radiation.
It would even be possible to plant some special genetically engineered plants in an outpost, while this would be practically impossible on the Moon due to vacuum.
This would help in humans to adjust more easily, as exposed periods to reduced gravity can cause serious medical problems to humans.
Both options would require billions of dollars to accomplish, but choosing the right option can allow man to start traversing around the stars in the next century.