Philip Shropshire of Three River Tech Review has written a nice rant about space exploration

I might add that if you were seriously concerned about the Martian ecosphere it would be nice if there were some environmentally sensitive types on the Red Planet. Who would be more responsible about making that choice as to whether to preserve the precious Martian bacterial life: The head of the Sierra Club or those lobbyists who want the EPA to lessen clean air standards? Who do you want making that choice to pave over the rare Martian ruins for the new mall: the head of Wal Mart or the head of Greenpeace? I think the choice is clear.

Three River Tech Review: A Left Argument For Space