Mars. Actual, real, Mars.
The data that the Curiosity rover (which finds itself on the red planet right now) will provide, is going to be useful in determining the place of life on Mars. Despite our neighbour planet being classified as "alien" in every way, looking at the above image taken on it gives a sense of familiarity. Indeed, the processes by which those rocks formed, as well as the processes by which life arises, are perhaps more universal than we perceive them to be.
The classic image of the Earth in the solar system portrays our mother planet as special and unique. Many people go as far as to suggest there is no life in the universe as there is on Earth. I for one am tempted to believe that there is life in the universe, wide and tall and diverse.
Does the knowledge about the Earth render itself useless on another planet? On the contrary, all knowledge acquired is as relevant to the rest of the universe as it is to our planet.
Curiosity is a very apt name for the rover on Mars. It also names the human attribute which has led to many amazing discoveries and inventions throughout civilisation. The path has already been set for humans to colonise the universe.