Mars

I don't think that environmental wingnuts would or
should be taken seriously when it comes to
terraforming other planets. The serious objections
will come from those who point out that there is no
good reason to go back down to the bottom of a gravity
well once we're at the top, and that the dismantlng of
Ceres for construction materials for space colonies
would provide 300 to 500 times the surface area of
Earth.