There are some who raise ethical questions about the colonisation of Mars. Opponents of colonisation and terraforming argue that invading an alien world and meddling with its ecosystem is nothing more than pollution and could be tantamount to genocide, should their actually be any alien life forms present on Mars. Currently, the robots and probes that we send up to Mars have to be sterilised within an inch of their lives, with no more that 300,000 contaminants on their surface, in order to avoid interplanetary contamination. There is no way of sterilising humans to this extreme and so human presence on Mars would inevitably lead to contamination. The comparison is often drawn with the colonisation of the Americas, and the idea of imposing our influence on a pristine environment is unthinkable to many. This stance is regarded by some as, in simple terms, a bit over the top. For a start it asserts that human culture acts outside of nature, and so a space colony would be unnatural, however, there is no real reason to think that homo sapiens advancing to the point of becoming a space-faring species is anything other that in our nature. The idea that we should purposefully restrict the boundaries of our own exploration, and potentially dooming our own species, because of concerns that we might be littering feels a little short-sighted. What we would have to be careful of is the amount of Earth resources it would take to sustain a Martian colony, and whether it would in fact be counter-productive to the whole "survival of the species" thing, by sapping the resources of Earth even further in our quest for space colonisation.
