Excellent point. But, that was then, and this is now, and after the Martians built "the face", they migrated to Earth because Mars' atmosphere was being blown away by global warming caused by Martian activity.
:') That's precisely my point -- if the atmosphere has thinned out and destroyed the supposed civilization, how can Hoaxland claim that it was previously "too thin to carve"? As is generally the case, he's full of it.