There is nothing that we can do to this planet that would render the environment a tenth as inhospitable as any known other planet.
IIRC we've not even found one that has free oxygen in the atmosphere yet. Even if we did, anything with that and water would be extremely exiting by the standards of exoplanets, even if it had an average temperature of 75 C which would kill humans.
Being the splendidly reactive stuff that it is, molecular oxygen doesn't survive very long in any atmosphere: generally there's always something that needs oxidising. So it's thought to be a good indicator of life, only arising on Earth after photosynthesis began:
Oh, we can do a lot to make that planet inhospitable. You are right that it would take quite a while to reach anything resembling martian levels and we still have a magnetic core which helps with many things.
But I wouldn't underestimate the multitude of ways in which this planet could be made inhospitable by us.
We are trusting a lot on the self-correcting power of nature on this planet, but we just don't know if there isn't some tipping point after which there is no return.
> There is nothing that we can do to this planet that would render the environment a tenth as inhospitable as any known other planet
That's yet to be proven - although not in my lifetime, I hope. One would hope that humankind would finally manage to do something before it gets as bad as on Venus, but I wouldn't bet on it...
Getting as bad as Venus would require as a minimum crashing a quarter of the entire asteroid belt into planet Earth, and that's assuming there's enough oxygen and carbon in those rocks.
Even if we burned 100% of all biomass on Earth, leaving it dead, it's still not close to Venus, where the "air" is so thick it's passed the critical point and no longer distinguishable from a liquid.
Even if we did that, the day length on Venus is longer than its year.
Free oxygen is not something that happens naturally, it requires a specific kind of life to constantly replenish as it gets consumed by surface oxidization.
It becomes really tangible just how much we drank the kool aid of capitalism when people can more easily imagine moving ontonexoplanet colonies than a future where the gain of the few capitalists isn't literally priorized above the survival of the human race.
Why do you think the next planet won't fall victim to the same mechanisms?
