Permanent probably does mean _eventually_ self-sustaining. Not in our lifetimes, maybe. But if we colonize mars in the next 3 decades it seems likely that in 1

Permanent probably does mean _eventually_ self-sustaining. Not in our lifetimes, maybe. But if we colonize mars in the next 3 decades it seems likely that in 1,000 years human life on Mars could be largely self-sustaining. When talking about creating planetary redundancy for human life 1,000 years is a small time-scale. We're guarding against 1/10,000,000 year kinds of extinction events on earth. It's unlikely that such an extinction event will happen on earth before a Mars colony could become reasonably self-sustaining. That said, it's important that we do it _eventually_, because over 100,000,000 years the odds of that earth wide extinction event goes way up.