Arguments Against Terraforming Mars
Time scales too long. How can any single organization,
government or otherwise, possibly commit themselves for 100s of
years?
Cost Benefits Uncertain. Almost nothing gets done without their being an economic driver. No such driver has been identified for Mars (look how little interest there is in the Moon!).
Destroying Mars' indigenous life. It might be the only form of life we find for thousands of years. What secrets might be lost about our past evolution?
Too early to begin. We might totally botch it! Think what we've done with Earth thus far. Why not wait until technology can work without causing undue harm?
Save our time and efforts for Home. The cost in money, personnel and resources will be ENORMOUS. Why work so hard to `doctor up' another planet, when we could work to fix up the beautiful one we already have?
There are no guarantees. The evolution of the Martian biosphere might be too unpredictable, wasting precious resources.
Preservation. There is something inherently beautiful about leaving Mars just as we found it-- not exploiting or commercializing it or bringing all our problems from Earth to rest on its pristine soil.
