It is probably a typo, but Mars doesn't have enough atmosphere to corrode things more than on Earth. If you need 50km long dredge, then it is a viable project

It is probably a typo, but Mars doesn't have enough atmosphere to corrode things more than on Earth. If you need 50km long dredge, then it is a viable project in future, just like now it is with space elevator. Apparently that type of dredge will be needed to extract materials from gas planets(and 50km might not be enough), so that dredge will have to be developed anyway. The most logical solution to make habitable world would be to bombard Venus with comets and small planets. They all have enough materials to stabilize Venus atmosphere and teraform it and also calculated bombarding can cause Venus to change axis and rotation.