Mankind as a species has been polluting the environment since day one and will continue to do so until the earth is no longer habitable.If as a species we crack the idea of travelling to another planet and colonising it we'll start the whole process over again[because we never seem to learn].This is not to say we shouldn't be trying to do something to at least slow the process-I doubt it can be stopped let alone reversed-but what the real answer is I don't know,renewable energy sources[wind farms and the like]they say can't or won't provide for all the needs,nuclear power they say is pollution free,but what of all the radioactive stuff left over when a nuclear station is decommissioned?They used to drop it in the ocean,but what happens when the sea and all the creatures living in the real depths break down the containers and concrete[or whatever they were filled with]and this stuff is released into the water?Meanwhile I'll keep driving my "gas guzzlers"until I'm either physically unable to do so or forced to by legislation.