Why Mars?

Mars is located in what is know as the "Goldilocks Zone", its not too cold, its not to hot, its just right. When a planet is in the Goldilocks zone, it is the perfect distance away from the sun so that it is not to  cold and it is not too hot. In our solar system, Earth and Mars are the only planets that are in the Goldilocks zone. For a planet to support life as we know it, said planet must be within the Goldilocks zone. The Goldilocks zone of a solar system my vary according to how big or hot that star is burning. If the star is burning very hot, then the Goldilocks zone will be much farther away than if it wasn't' burning very hot. This is the whole basis behind why we are so interested in Mars. If Venus was in the Goldilocks zone instead of Mars, then we would be working toward going there. If a planet is not considered to be within the Goldilocks zone, then is is automatically ruled out for a candidate for colonization. Although, just because a planet is not within the Goldilocks zone, that does not necessarily mean that it can not support some sort of life. Life as we know it depends on liquid water which requires a certain temperature to stay in liquid form. Although, for all we know, there could be some kind of life, whether it be complex for just single cell organisms, could depend on something else like liquid methane which exists in a stable liquid form on Saturn's moon, Titan (a subject for another post). If life does exist that depends on some other liquid, then that would create another Goldilocks zone for that certain liquid, but, frankly, that would be unimportant to the human race since humans probably would be able to live in that zone.