> surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the ast

> surely building a couple layers of solar sail material to shield the planet, stockpiling ozone generators to repair the damage quickly, gently nudging the asteroid, or simply digging some holes/eating a gas giant and weathering the storm, would be easier The assumption is that we have a problem getting anything off the planet. All these would require some good rocket engineering. I agree with everything else here a lot.