The human race has existed for a relatively short time, and since the beginning we have grown in population and expanded our domain. Restricting the colonization of other planets goes against human nature, and would ultimately lead to the end of humanity. Aside from our Moon, Mars could be our best starting point for space colonization. Our need to colonize other worlds is great, and the ability is in our reach. With available technology, a manned mission to mars would have a fairly high chance of success.
Humans are known for adapting to various environments. We have walked, rode, sailed and even flew to discover and colonize most of the Earth. Our population continues to grow, and the earth does not. Living on other planets is the only option that allows humanity to flourish. In millions of years, our sun will even expand and envelop earth. At that point, regardless of what we have done to live on earth, our time on this planet will be over. That or a number of natural disasters could wipe out our entire race, just as with the dinosaurs. Living on Mars would help prevent something like that from wiping out possibly the only intelligent lifeforms in the universe.
Mars has many resources necessary for humans to live. Water ice is even known to exist. The martian atmosphere is abundant with carbon dioxide. Although this atmosphere would be impossible for us to breathe, our plants would fare much better. All of the resources available, as well as equipment available, make Mars a very suitable location for long term habitats. Terraforming the planet could also eventually lead to humans living openly on the martian surface. Once humans have lived on Mars, the entire solar system and beyond could be available to us.
A mission to Mars today would dangerous, but we are certainly capable of accomplishing it. NASA, Russia, and several civilian groups are even working toward the very goal of living on Mars. The planet Mars is a suitable candidate for human exploration and could supply many necessary resources for colonies. Human technology even makes the possibility of living on Mars a very real thing. Humanity has both the need and the capability for living on planets other than Earth. The earth is doomed inevitably, but humanity has the potential to last beyond. The earth was our beginning, let Mars be the next chapter.